Getting Started with MariaDB

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Getting Started with MariaDB
Learn how to use MariaDB to store your data easily and
hassle-free
Daniel Bartholomew
BIRMINGHAM - MUMBAI
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Getting Started with MariaDB
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First published: October 2013
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Credits
Author
Project Coordinator
Daniel Bartholomew
Proofreader
Reviewers
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P. R. Karthik
Daniel Parnell
Indexers
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About the Author
Daniel Bartholomew has been using Linux since 1997 and databases since
1998. He has written dozens of articles for various magazines, including The Linux
Journal, Linux Pro, Ubuntu, User and Tux.
Daniel has been involved with the MariaDB project shortly after it began in
early 2009. He currently works for SkySQL and splits his time between MariaDB
documentation and maintaining the bits and pieces (including build, e-mail, web,
and other servers) that keep the MariaDB project running smoothly. In addition to
his day-to-day responsibilities, Daniel also serves as the MariaDB release coordinator
and has been deeply involved with almost every MariaDB release.
He lives in Raleigh, North Carolina, USA with his lovely wife and four children.
I'd like to thank Amy, Ila, Lizzy, Anthon, and Rachel for their
patience with me throughout the writing of this book. Thanks also to
Vladislav Vaintroub, Sanja Byelkin, Roger Bartholomew, and others
who were very helpful at various points during the project. Lastly,
I'd like to thank Monty and the rest of the MariaDB team for the
excellent database that they've created.
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About the Reviewers
P. R. Karthik started his career as a MySQL DBA. Currently, he is working as a
Senior MySQL DBA in Yahoo. They are managing one of the biggest MySQL farms
in the world.
I would like to thank my parents and friends for their support with
reviewing this book.
Daniel Parnell lives in Melbourne, Australia. He started messing around with
computers when he was very young. His first computer was an AIM65 with a 4 K of
RAM, BASIC and Forth in ROM, and no storage. From there, he tinkered with various
home computers ranging from the Apple II to the Commodore Amiga. These days
Daniel works on web and desktop apps. When Daniel is not programming or tinkering
with his latest hardware project, he is spending time with his wife and two children.
Stephane Varoqui is a senior MariaDB and MySQL consultant at SkySQL. He
is based in Paris. Before joining SkySQL in 2011, he worked at MySQL/Sun/Oracle
as a lead MySQL consultant in the Europe/Middle East/Africa (EMEA) region for
six years.
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Table of Contents
Preface1
Chapter 1: Installing MariaDB
7
Choosing a MariaDB series
8
The development series
8
The stable series
9
The maintenance series
9
Installing MariaDB on Windows
10
Installing MariaDB on Mac OS X
13
Installing MariaDB on Debian, Ubuntu, and Linux Mint
14
Installing MariaDB on Fedora, Red Hat, and CentOS
15
Installing MariaDB on other Linux distributions
17
MariaDB package security
18
After the installation
18
Troubleshooting installation issues
19
Summary20
Chapter 2: Configuring MariaDB
21
Filesystem layout for MariaDB
21
Filesystem layout for Windows
21
Filesystem layout for Linux
22
Modular configuration on Linux
23
The MariaDB configuration file
25
Comments
25
Groups26
Options which do not require values
26
Options which require values
27
Options, options everywhere
28
Activating configuration changes
28
Summary29
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Table of Contents
Chapter 3: MariaDB Security
31
Chapter 4: MariaDB User Account Management
41
Chapter 5: Using MariaDB
51
Securing MariaDB in ten seconds
32
Connecting safely
34
Server security
36
Building security
37
Internal network security
38
Internet security
39
Summary39
User privileges
Global administrative privileges
Database, table, and column privileges
Miscellaneous privileges and limits
Creating users
Granting permissions
Adding and removing privileges
Showing grants
Changing passwords
Removing users
Summary
Running the mysql command-line client
Using a database
Listing all databases on a server
Creating and dropping databases
Creating a database
Dropping a database
Creating, altering, and dropping tables
Creating a table
Showing the command used to create a table
Exploring the structure of a table
Altering a table
Adding a column
Modifying a column
Dropping a column
Dropping a table
Selecting, inserting, updating, and deleting data
Inserting data
Updating data
Deleting data
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41
42
42
43
44
45
47
47
48
48
49
51
52
53
54
54
55
56
56
58
59
60
60
60
61
61
61
62
63
64
Table of Contents
Reading data
64
Summary68
Chapter 6: MariaDB Maintenance
69
MariaDB log files
69
The all-important binary log
69
The error log
70
The general query log
71
The slow query log
71
Optimizing and tuning MariaDB
72
Backing up MariaDB
73
Basic backups with mysqldump
73
Restoring and importing data with mysqlimport
75
Making backups of MyISAM tables quickly with mysqlhotcopy
75
Making cold backups
76
Checking and repairing tables
76
Checking and optimizing tables with mysqlcheck
76
Repairing tables
77
Summary78
Appendix: MariaDB Next Steps
79
Index81
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Preface
Databases are all around us. Almost every website we visit and nearly every store
we shop at has a database (or several) working quietly behind the scenes. The same
goes for banks, hospitals, government agencies, theaters, doctors, amusement parks,
and police departments. All use databases to store, sort, and analyze information.
This information comes in many forms and can be anything that can be stored
electronically inside a computer. This includes books, catalogs, addresses, names,
dates, finances, pictures, money, passwords, documents, preferences, tweets, posts,
likes, blogs, articles, and many more. Databases are one of the primary pillars of
modern life.
Your posts on Facebook and tweets on Twitter are stored in a database. All your
financial information at your bank is stored in a database and so is your purchase
history at your favorite online retailer. Your progress in your favorite online game?
You guessed it. The record of when you last paid your water bill. You just can't get
away from databases. They are quite literally everywhere.
There is a new database that has caught attention of the database community over
the past few years like few others have. Its name is MariaDB; it is named after the
youngest daughter of its creator, Michael "Monty" Widenius. First released in 2009,
MariaDB may be relatively new, but it has a stellar parentage. It's a next-generation
version of the popular MySQL database, also created by Monty. (you may have
heard of it, but don't worry if you haven't).
MariaDB is open source. This means the source code is freely downloadable and
is governed by a license that helps ensure the source code stays free and open to
all. The MariaDB developers have also kindly provided installers for various
operating systems.
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Preface
Since its first release, MariaDB has gained a large, loyal following quicker than
almost any other database. Today it powers tens of thousands of websites, big
and small and is the database of choice for many companies in a wide variety of
industries around the world, with hundreds of thousands of users.
The great news is that we can install and use it ourselves, right now, on our personal
laptop and desktop computers. For all of its power, and make no mistake, MariaDB
is a very powerful and capable database; it is very easy to install and use.
This book provides an introduction to MariaDB—enough to get us started. Don't
worry if you've never used a database before, they're not that hard to understand.
Before we know it we'll be on our way to becoming an expert database administrator
(DBA). But even if we never move beyond just tinkering or playing around with
MariaDB, we'll have learned about one of the fundamental technologies of our times.
Not a bad accomplishment over a weekend or two.
What this book covers
Chapter 1, Installing MariaDB, explains how to install MariaDB on Windows and Linux.
Chapter 2, Configuring MariaDB, explains the basics of configuring MariaDB,
including the location of the configuration files, and how to set common
configuration options.
Chapter 3, MariaDB Security, gives out the best practices for MariaDB security and
how to easily secure a new MariaDB installation.
Chapter 4, MariaDB User Account Management, explains how to add and administer
MariaDB user accounts.
Chapter 5, Using MariaDB, explains the basics of using MariaDB, including adding
and dropping databases and tables, and selecting, inserting, and updating data.
Chapter 6, MariaDB Maintenance, explains how to maintain your MariaDB database
and keep it running smoothly.
Appendix, MariaDB Next Steps, will provide the user with the locations of official
sources of information and documentation.
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Preface
What you need for this book
To get the most out of this book, we will need a computer running Windows, with any
version from XP through Windows 8, a computer running MacOS X, or a computer
running one of the following Linux distributions: Ubuntu, Mint, Debian, Fedora,
CentOS, or Red Hat. MariaDB runs on many more operating systems and distributions,
but those are the ones that are specifically mentioned and talked about in this book.
To install MariaDB we will need an Internet connection and the necessary
administrative rights to install software.
To edit MariaDB configuration files, we will need a text editor. Notepad is a good
universal choice on Windows. TextEdit and TextWrangler work well on MacOS
X. There are many text editors on Linux, just pick a favorite: Vim, gedit, nano,
emacs, and many more are all good. A word processor such as Word, Wordpad,
OpenOffice, or Libre Office will not work.
No other software is required.
Who this book is for
This book is for anyone interested in learning about MariaDB or databases in general.
It doesn't assume any prior database experience, however it does assume prior
computer experience. You should be comfortable with installing software, editing
configuration files, and using the command line or terminal.
Conventions
In this book, you will find a number of styles of text that distinguish between
different kinds of information. Here are some examples of these styles, and an
explanation of their meaning.
Code words in text are shown as follows: "All of them can be changed later by
editing the my.ini file."
A block of code is set as follows:
SET PASSWORD FOR <user> = PASSWORD('<password>');
When we wish to draw your attention to a particular part of a code block, the
relevant lines or items are set in bold:
SET PASSWORD FOR <user> = PASSWORD('<password>');
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Preface
Any command-line input or output is written as follows:
sudo mv -vi MariaDB.repo /etc/yum.repos.d/
New terms and important words are shown in bold. Words that you see on the
screen, in menus or dialog boxes for example, appear in the text like this: "Click on
Finish to quit the installer."
Warnings or important notes appear in a box like this.
Tips and tricks appear like this.
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Preface
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Installing MariaDB
Before we can start using MariaDB, we have to install it. The MariaDB source
code can be compiled to run on a wide variety of different platforms and system
architectures, but there are pre-compiled packages available for Windows and Linux
which make the process much easier.
There are several packages types, including the source code:
• Windows MSI packages
• Linux YUM packages
• Linux APT packages
• Linux and Windows binaries
• Source code
Windows MSI packages are for computers and servers running Windows 8,
Windows XP, and everything in between. Linux .rpm packages are used on
distributions, such as Fedora, CentOS, and Red Hat, which use the Yellow Dog
Updater, Modified (YUM) package manager. Linux .deb packages are used on
distributions, such as Debian and Ubuntu, which use the Advanced Packaging Tool
(APT) package manager. We will cover how to install all these types in this chapter.
We will cover the fourth type, Linux and Windows Binaries, briefly. These packages
are mainly useful to experienced users of MariaDB who have nonstandard setups.
The Windows binaries come in a ZIP file (.zip) and the Linux binaries in a gzipped
tar file (.tar.gz).
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Installing MariaDB
Even though MariaDB binaries are recommended for more experienced users,
installing them is not especially difficult. Check the following links for the official
instructions for installing the Linux and Windows binary packages, respectively:
• https://mariadb.com/kb/en/installing-mariadb-binary-tarballs
• https://mariadb.com/kb/en/installing-mariadb-windows-zippackages
We will also go over how to install MariaDB on Mac OS X. Packages for it are not
supplied by the MariaDB developers, but by a third party.
The choice of which type of package to install is an easy one, just use whichever is
appropriate for your system. If you are on Windows, use the MSI package. If you are
on Ubuntu or Debian, use the APT packages. And if you are on Red Hat, Fedora, or
CentOS, uses the YUM packages.
The next few sections contain instructions for each type, but before we get to that we
need to talk about series. And no, it has nothing to do with baseball, but it does lend
itself to a baseball analogy.
Choosing a MariaDB series
MariaDB development proceeds along multiple development tracks called series.
There is a stable series and several maintenance series. Often, there is also a
development series. This is similar to the Debian practice of having both a stable
and unstable version.
The development series
The development series of MariaDB is where major new features and capabilities are
introduced. Think of this like minor league baseball where the up and coming future
stars are introduced and are polished and honed to perfection. At any given time,
the quality of the current development release could range from Alpha (which has
no guarantees that it will even work reliably) to Beta (which is feature complete but
generally needs lots of bug fixing and testing) to Release Candidate (which is ready
for general use except for some additional testing and minor bug fixing).
During the development cycle, there will generally be several alpha releases, where
new features are introduced, followed by a couple beta releases where the code
is refined and polished, followed by one or two RC releases where final fixes and
polishing take place. The final step for any development series is when it is declared
stable and moves into the major league stable series.
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Chapter 1
If the current development series release is an RC release, we may
want to choose that over the current stable release. Otherwise, it is
generally best to stick with whatever the current stable release is.
The stable series
For most users just starting out, whatever series is marked stable is the one to
use. This is the major league series. The best and most complete version currently
available. After a development series has reached a sufficient level of quality to
be considered stable, it is promoted to this series and becomes the recommended
version of MariaDB.
After being marked as stable, the MariaDB Foundation has a policy that major
MariaDB version will be well supported with bug and security fixes and
maintenance releases for a period of at least five years. This is regardless of whether
it is the current stable series, or if it is one of the maintenance series. It all depends on
when it first became stable.
The maintenance series
When a series moves from development to stable, whatever series was stable is
moved to the maintenance series. This means that it will still receive bug fixes but it
is no longer the recommended or preferred release of MariaDB. Think of it as the hall
of fame—full of great previous releases of MariaDB that, while still excellent, have
been replaced by a new generation. At any given time there may be three, four, or
more MariaDB major versions in the maintenance series.
We'll now go through installing MariaDB for each of the major operating systems.
First Windows, then Mac OS X, then Debian and Ubuntu Linux, then Fedora, Red
Hat, and CentOS Linux, and lastly other Linux distributions.
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Installing MariaDB
Installing MariaDB on Windows
There are two types of MariaDB downloads for Windows: ZIP files and MSI
packages. As mentioned previously, the ZIP files are similar to the Linux binary
.tar.gz files and they are only recommended for experts who know they want it.
If we are starting out with MariaDB on Windows, it is recommended to use the MSI
packages. Here are the steps to do just that:
1. Download the MSI package from https://downloads.mariadb.org/. First
click on the series we want (stable, most likely), then locate the Windows
64-bit or Windows 32-bit MSI package. For most computers, the 64-bit MSI
package is probably the one that we want, especially if we have more than 4
Gigabytes of RAM. If you're unsure, the 32-bit package will work on both 32bit and 64-bit computers.
2. Once the download has finished, launch the MSI installer by doubleclicking on it. Depending on our settings we may be prompted to launch it
automatically. The installer will walk us through installing MariaDB.
3. If we are installing MariaDB for the first time, we must be sure to set the root
user password when prompted.
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Chapter 1
4. Unless we need to, don't enable access from remote machines for the root
user or create an anonymous account. We'll cover creating regular user
accounts in Chapter 4, MariaDB User Account Management.
5. The Install as service box is checked by default, and it's recommended to
keep it that way so that MariaDB starts up when the computer is booted. The
Service Name textbox has the default value MySQL for compatibility reasons,
but we can rename it if we like.
6. Check the Enable networking option, if you need to access the databases
from a different computer. If we don't it's best to uncheck this box. As with
the service name, there is a default TCP port number (3306) which you can
change if you want to, but it is usually best to stick with the default unless
there is a specific reason not to.
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Installing MariaDB
7. The Optimize for transactions checkbox is checked by default. This setting
can be left as is.
8. There are other settings that we can make through the installer. All of them
can be changed later by editing the my.ini file (more on that in Chapter 2,
Configuring MariaDB), so we don't have to worry about setting them right
away.
9. If our version of Windows has User Account Control enabled, there will be
a pop-up during the installation asking if we want to allow the installer to
install MariaDB. For obvious reasons, click on Yes.
10. After the installation completes, there will be a MariaDB folder added to the
start menu. Under this will be various links, including one to the MySQL
Client, which we will find out more about in Chapter 5, Using MariaDB).
If we already have an older version of MariaDB or MySQL running
on our machine, we will be prompted to upgrade the data files for the
version we are installing, it is highly recommended that we do so.
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Chapter 1
11. Eventually we will be presented with a dialog box with an installation
complete message and a Finish button. If you got this far, congratulations!
MariaDB is now installed and running on your Windows-based computer.
Click on Finish to quit the installer.
To learn about installing MariaDB on Mac OS X or Linux, read on. Otherwise, feel
free to skip to the After the installation section at the end of this chapter.
Installing MariaDB on Mac OS X
One of the easiest ways to install MariaDB on Mac OS X is to use Homebrew, which
is an Open Source package manager for that platform. Before you can install it,
however, you need to prepare your system. The first thing you need to do is install
Xcode; Apple's integrated development environment. It's available for free in the
Mac App Store.
Once Xcode is installed you can install brew. Full instructions are available on
the Brew Project website at http://mxcl.github.io/homebrew/ but the basic
procedure is to open a terminal and run the following command:
ruby -e "$(curl -fsSL https://raw.github.com/mxcl/homebrew/go)"
This command downloads the installer and runs it. Once the initial installation is
completed, we run the following command to make sure everything is set up properly:
brew doctor
The output of the doctor command will tell us of any potential issues along with
suggestions for how to fix them. Once brew is working properly, you can install
MariaDB with the following commands:
brew update
brew install mariadb
Unlike on Linux and Windows, brew does not automatically set up or offer to set
up MariaDB to start automatically when your system boots or start MariaDB after
installation. To do so, we perform the following command:
ln -sfv /usr/local/opt/mariadb/*.plist ~/Library/LaunchAgents
launchctl load ~/Library/LaunchAgents/homebrew.mxcl.mariadb.plist
To stop MariaDB, we use the unload command as follows:
launchctl unload ~/Library/LaunchAgents/homebrew.mxcl.mariadb.plist
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Installing MariaDB
To learn about installing MariaDB on Linux, read on. Otherwise, skip to the After the
installation section at the end of this chapter.
Installing MariaDB on Debian, Ubuntu,
and Linux Mint
The procedure for installing MariaDB on Debian, Ubuntu, and Linux Mint is easy,
and starts with a visit to the Repository Configuration Tool at:
http://downloads.mariadb.org/mariadb/repositories
This tool is used for APT-based Linux distributions such as Debian, Ubuntu, and
Mint, YUM-based Linux distributions such as Fedora, CentOS, and Red Hat, and
other distributions that have support for MariaDB built-in such as Mageia, Arch
Linux, and openSUSE.
Before using the tool you need to know which version of Ubuntu, Debian, or Mint to
use. If you do not know, an easy way to find out is with the following command:
cat /etc/lsb-release
Type the command into the terminal and you will get an output similar to the
following:
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=10.04
DISTRIB_CODENAME=lucid
DISTRIB_DESCRIPTION="Ubuntu 10.04.4 LTS"
The output shows that this machine is running Ubuntu 10.04 LTS "Lucid". So using the
Repository Configuration Tool, click on Ubuntu, then 10.04 LTS 'lucid', then on the
version or series of MariaDB you want to install. Lastly, click on the mirror you want
to use. The tool will then output three pieces of text. The first are the commands to add
the MariaDB repository to your system. The second contains the commands to install
MariaDB, and the third contains the text and alternate instructions in case adding the
repository using the first set of instructions did not work.
For example, the generated commands for adding a repository for MariaDB 10.0
on the 64-bit version of Ubuntu 12.04 LTS "Lucid" and using the osuosl mirror
are as follows:
sudo apt-get install python-software-properties
sudo apt-key adv --recv-keys \
--keyserver keyserver.ubuntu.com 0xcbcb082a1bb943db
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sudo add-apt-repository \
'deb http://ftp.osuosl.org/pub/mariadb/repo/10.0/ubuntu precise main'
The first command installs the python-software-properties package, which
contains the helper command we will use. The second command installs the GPG
key that is used to sign MariaDB packages. See the MariaDB package security section
later in this chapter for more information on this. The third command adds the
repository using the add-apt-repository command.
The displayed installation commands are as follows:
sudo apt-get update
sudo apt-get install mariadb-server
The mariadb-server package depends on the other MariaDB packages, so these two
commands are all we need to install MariaDB. Once the second apt-get command
finishes, MariaDB will be installed and running. Congratulations!
Jump ahead to the MariaDB package security section if you're interested in the
MariaDB signing keys or skip to the After the installation section if you want to start
using MariaDB right away.
Installing MariaDB on Fedora, Red Hat,
and CentOS
The procedure for installing MariaDB on Fedora, Red Hat, and CentOS makes use
of the Yellowdog Updater, Modified (YUM) package manager. There are two steps:
first, create a repo file for MariaDB and second, install MariaDB.
To generate the required text for the repo file, we visit the MariaDB Repository
Configuration Tool at: http://downloads.mariadb.org/mariadb/repositories/.
This tool is used for both APT-based Linux distributions such as Debian and Ubuntu,
and YUM-based Linux distributions such as Fedora, CentOS, and Red Hat.
Click on the distribution we are using, the release available, and the version of
MariaDB we want to install. After doing so, contents of the appropriate repo file will
be displayed.
For example, the generated text for MariaDB 10.0 on the 64-bit version of CentOS 6 is:
# MariaDB 10.0 CentOS repository list - created 2013-03-09 20:58 UTC
# http://mariadb.org/mariadb/repositories/
[mariadb]
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name = MariaDB
baseurl = http://yum.mariadb.org/10.0/centos6-amd64
gpgkey=https://yum.mariadb.org/RPM-GPG-KEY-MariaDB
gpgcheck=1
The gpgkey line tells YUM where the MariaDB signing key is located. The gpgcheck
line directs Yum to always use the signing key to verify the MariaDB packages.
The first time we install MariaDB our system will not have the key so Yum will
download it and install it. If Yum has never used the key before it will ask for
confirmation whether it is OK to import the key. See the MariaDB package security
section for more information on the MariaDB signing key.
Copy and paste the generated text from the repository configuration tool into a
file using our favorite text editor. Naming the file something descriptive, such as
MariaDB.repo, is recommended. Move the file to the /etc/yum.repos.d/ folder
using a command similar to the following:
sudo mv -vi MariaDB.repo /etc/yum.repos.d/
Once the file is in place, we are ready to install MariaDB. Installing MariaDB from
the command line is as simple as:
sudo yum install MariaDB-server MariaDB-client
The capitalization of the package names is important. If we type mariadb-server
instead of MariaDB-server, we'll get a package cannot be found error.
YUM will gather in all of the dependencies for MariaDB and present us with a list
of things we need to install. If we are installing MariaDB on a new system, the list of
packages YUM installs because of dependencies could be quite large. The following
screenshot shows that there are more than 41 dependent packages that will be installed
when we install MariaDB.
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Chapter 1
After answering y, the installation will get going and we will be prompted to accept
the GPG signing key. We verify the fingerprint with y. Yum will then continue
downloading and installing MariaDB and will end with a Complete! message.
As a final step of the installation, we start MariaDB with the following command:
sudo /etc/init.d/mysql start
If everything has gone well, we will see output similar to the following:
[dbart@fedora18-amd64 ~]$ sudo /etc/init.d/mysql start
Starting MySQL..... SUCCESS!
MariaDB is now installed and running. Congratulations! Jump ahead to the After the
installation section or continue on to read about the MariaDB Package Security.
Jump ahead to the MariaDB package security section if you're interested in the
MariaDB signing keys or skip to the After the installation section if you want to start
using MariaDB right away.
Installing MariaDB on other Linux
distributions
MariaDB is also available on several other Linux distributions and even if no formal
packages are provided the MariaDB developers provide generic Linux binaries that
work with many versions of Linux. Instructions on how to install and use the generic
binaries are available at https://mariadb.com/kb/en/installing-mariadbbinary-tarballs/.
Before installing the binary packages, however, it is worth our while to look
in our distribution's package manager to see if MariaDB is already there. For
example, Mageia, Arch Linux, openSUSE, and others all include MariaDB in their
distributions' repositories. For those Linux distributions (including these three) that
the MariaDB developers are familiar with, installation instructions are provided
using the MariaDB repository configuration tool (https://downloads.mariadb.
org/mariadb/repositories/).
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Installing MariaDB
MariaDB package security
The packages provided by the MariaDB developers are signed with a security key
so that they can be verified by package managers such as Yum and Apt. The key
signing and verification infrastructure on Linux is called Gnu Privacy Guard (GPG).
It is a compatible Open Source version of Pretty Good Privacy (PGP) which is an
industry standard data encryption, decryption, and verification system.
The identification number (GPG ID) of the MariaDB signing key is
0xcbcb082a1bb943db. For long-time users of GPG, this ID may seem a little long.
That's because until recently, it was common to share a short form of the GPG ID.
This is discouraged now because of a GPG's vulnerability; however many utilities
will still display the short form by default. The long form of the ID is more secure,
so this is what the MariaDB developers share when talking about the key. But,
in case we want it, the short form of the ID is 1BB943DB (it's just the last eight
characters of the long form ID). For the extra cautious, the full key fingerprint is:
1993 69E5 404B D5FC 7D2F E43B CBCB 082A 1BB9 43DB
The key IDs and fingerprint are also posted in the MariaDB Knowledgebase,
which is the official location of the MariaDB documentation and is available at
https://mariadb.com/kb/en/gpg/.
By checking the signature of the packages, Linux package managers, and more
importantly, we, can verify whether the package that comes from the MariaDB
developers and hasn't been tampered with since they created it.
When configuring the MariaDB repository on Debian and Ubuntu, and during the
initial MariaDB install on Fedora, Red Hat, and CentOS, an important task is to
import the signing key. It's a good idea to verify the key by comparing it to the IDs
and the fingerprint when doing so. Thankfully, this is a one-time operation. Once
the key is imported the process is fully automatic. We'll only be notified if the
signature check fails.
After the installation
After installing MariaDB, we can quickly test that MariaDB is up and running by
opening a terminal or command-line window and running the following command
(on Windows we can also open the mysql client .exe in the MariaDB folder):
mysql -u root -p
This command connects to MariaDB as the root user (-u root) and prompts for the
password of that user (-p). When prompted, type in the password configured during
the install. If no password was set during the install, remove -p. Until a password is
set we can connect without a password.
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Chapter 1
Not having a password for the root user can be dangerous! If you did
not set one during the installation, be sure to set one immediately after
the install following the instructions in Chapter 3, MariaDB Security.
If MariaDB has been successfully installed and started, we should see something
similar to the following screenshot when connecting using the previous command
to launch the mysql command-line client:
If you get the MariaDB command-line prompt as illustrated in the preceding
screenshot, congratulations! You've just installed MariaDB and can successfully
connect to the server using the command-line client. You can quit the command-line
client for now. Don't worry; we'll come back to it soon.
Troubleshooting installation issues
The MariaDB installers work very well. And they are tested and retested constantly.
Occasionally issues with either installing MariaDB or running it for the first time are
discovered, but they are almost always fixed promptly so that users are not affected.
If we do happen to run into an issue when trying to start MariaDB, what should
we do?
The first thing we should do is look in the error log. The MariaDB error log is either
stored with the system logfiles (for example, under /var/log/ on Linux) or in the
MariaDB data directory. Common locations for the MariaDB data directory include
/var/lib/mysql/ on Linux, C:\Program Files\MariaDB <version>\data\ on
Windows (<version> is the version number of MariaDB we are using), and /usr/
local/var/mysql/ on Mac OS X. The error logfile itself will either be called mysql.
err or hostname.err where hostname is the name we've given our computer. It is
also worth noting that the name and location of the logfile can be customized by the
my.cnf or my.ini file. The next chapter on configuring MariaDB will go into this file
and its location.
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Installing MariaDB
Each entry inside the error logfile consists of a timestamp and a description of what
went wrong at that timestamp. Sometimes the information given is enough for us
to figure it out ourselves, but sometimes we may need to ask for help. We shouldn't
feel bad if we can't figure an error out, even experts are sometimes stumped! If we do
need to ask for help, the resources listed on the following page, especially the Maria
Discuss mailing list and the official IRC channel can help greatly: https://mariadb.
com/kb/en/where-are-other-users-and-developers-of-mariadb/
Summary
In this chapter we installed MariaDB. Our next task is to configure it, which just so
happens to be the subject, and title, of the next chapter.
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Configuring MariaDB
MariaDB is installed with a generic configuration suitable for light, casual use. This
is perfect for giving MariaDB a try but hardly suitable for a production database
application, or even a moderately busy website database. There are thousands of
ways to tweak the settings to get MariaDB to perform the way we need it to. Many
books have been written on this subject. In this chapter, we'll just cover the basics
that are enough to comfortably edit the MariaDB config files and get to know our
way around; think of it as a highlights tour.
Filesystem layout for MariaDB
A MariaDB installation is not a single file or even a single directory, so the first
stop on our tour is a high-level overview of the filesystem layout. We'll start with
Windows, and then move on to Linux.
Filesystem layout for Windows
On Windows, MariaDB is installed under a directory named with the
following pattern:
C:\Program Files\MariaDB <major>.<minor>\
The following is the location for MariaDB 10.0:
C:\Program Files\MariaDB 10.0\
The only alteration of this location, unless we change it during the installation, is
when the 32-bit version of MariaDB is installed on a 64-bit version of Windows. In
that case, the default MariaDB directory is at the following location:
C:\Program Files x86\MariaDB <major>.<minor>\
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Configuring MariaDB
Under the MariaDB directory on Windows, there are four primary directories: bin,
data, lib, and include. There are also several configuration examples and other
files under the MariaDB directory and a couple of additional directories (docs and
Share), but we won't go into them here. The bin directory is where the .exe files
of MariaDB are located. The data directory is where databases are stored; it is also
where the primary MariaDB configuration file, my.ini, is stored. We'll talk about
this file later in the The MariaDB configuration file section. The lib directory contains
various library and plugin files. Lastly, the include directory contains files useful for
application developers.
We don't need to worry about the bin, lib, and include directories, just be aware
that they exist and know what they contain. The data directory is where we'll spend
most of the time in this chapter.
Feel free to read the next section which explains the location of MariaDB files on
Linux systems, or jump ahead to the The MariaDB configuration file section.
Filesystem layout for Linux
On Linux distributions MariaDB follows the default filesystem layout available for
Linux. For example, MariaDB binaries are placed under /usr/bin/, libraries are
placed under /usr/lib/, manual pages are placed under /usr/share/man/, and
so on. However, there are some key MariaDB-specific directories and file locations
everyone should know about. Two of them have locations that are the same for the
systems based on Advanced Package Tool (APT) and Yellow Dog Updater, Modified
(YUM). These locations are /usr/share/mysql/ and /var/lib/mysql/ respectively.
The /usr/share/mysql/ directory contains helper scripts that are used during
the initial installation of MariaDB, translations (so we can have error and system
messages in different languages), and character set information. The /var/lib/
mysql/ directory is the default location for our actual database data. We don't need
to worry about the contents of /usr/share/mysql/. It's enough to know that it
exists and contains important files. Also, there is not much need to worry about the
/var/lib/mysql/ directory. MariaDB will handle the contents of that directory
automatically; just know that it exists.
The next directory is where MariaDB plugins are stored. On Debian and Ubuntu
systems the directory is at the following location:
/usr/lib/mysql/plugin/
As with /usr/share/mysql/, we don't need to worry about the contents of /usr/
lib/mysql/. It's enough to know that it exists and contains important files. Also, if in
the future we install a new MariaDB plugin, this directory is where it will go.
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Chapter 2
On YUM distributions such as Fedora, Red Hat, and CentOS, the location of the
plugin directory varies depending on whether our system is 32 bit or 64 bit. If
unsure, just look in both. The possible locations are as follows:
/lib64/mysql/plugin/
/lib/mysql/plugin/
A basic rule of thumb is that if we don't have a /lib64/ directory, we have the 32-bit
version of Fedora, Red Hat, or CentOS installed.
The last directory we want to know is only found on APT-based distributions
(Debian and Ubuntu) by default. It is as follows:
/etc/mysql/
The /etc/mysql/ directory is where configuration information for MariaDB is
stored. Specifically in the following two locations:
/etc/mysql/my.cnf
/etc/mysql/conf.d/
There are some other files in the directory, but we can ignore them for now.
We'll look into more detail of the my.cnf file in the The MariaDB configuration
file section. And we'll talk about the conf.d directory in the Modular configuration
on Linux section.
Fedora, Red Hat, and CentOS systems don't have a /etc/mysql/ directory by
default, but they do have the my.cnf file and a my.cnf.d directory. They are at the
following two location:
/etc/my.cnf
/etc/my.cnf.d/
The my.cnf files function the same on all Linux versions and on Windows, where it
is often named my.ini. The my.cnf.d and conf.d directories, despite their different
names, serve the same purpose. We'll spend the rest of our highlights tour talking
about the my.cnf file after going over the my.cnf.d and conf.d directories. Feel free
to skip the next section if you are working with Windows.
Modular configuration on Linux
The my.cnf.d and conf.d directories are special locations for MariaDB configuration
files. They are found on MariaDB releases for Linux such as Debian, Ubuntu, Fedora,
Red Hat, and CentOS. By default, they are at the following two locations:
/etc/my.cnf.d/
/etc/mysql/conf.d/
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Configuring MariaDB
We will only have one of them and regardless of which one we have, they function
the same. The basic idea is to allow the package manager (APT or YUM) to be able to
install packages for MariaDB, which include additions to the MariaDB configuration
file without needing to edit or change the main my.cnf file. It's easy to imagine the
harm that would be caused if we installed a new plugin package and it overwrote
a carefully crafted and tuned configuration file. With these special directories, the
package manager can simply add a file to the appropriate directory and be done.
The MariaDB server, or any client or utility included with MariaDB, will read both
the main my.cnf file and any files in the my.cnf.d or conf.d directories that have
the extension .cnf when it starts.
For example, MariaDB includes a plugin called feedback whose sole purpose is to
send back anonymous statistical information to the MariaDB developers. They use
the information to help guide future development efforts. It is disabled by default
but can easily be enabled by adding feedback=on to the [mysqld] group of the
MariaDB configuration file (we'll talk about configuration groups in the following
section). Instead of adding this to the main configuration file, we can instead create a
file called feedback.cnf with the following contents:
[mysqld]
feedback=on
Place this file in the my.cnf.d or conf.d directory and when we start or restart the
server the feedback.cnf file will be read and the plugin will be turned on. Doing
this for a single plugin on a solitary MariaDB server may seem like too much work,
but suppose we have 100 servers, and further assume that since the servers are
different, each of them has a slightly different my.cnf configuration file. Without
using these directories to turn on the feedback plugin on all of them, we would have
to connect to each server in turn and manually add feedback=on to the [mysqld]
group of the file. This would get tiresome and there is also a chance that we might
make a mistake with one, or several of the files we edit, even if we try to automate
the editing in some way. Copying a single file to each server that only does one thing
(turn on the feedback plugin in our example) is much faster, and much safer. And, if
we have an automated deployment system in place, copying the file to every server
can be almost instant.
One thing to be aware of is that since the configuration settings in the my.cnf.d or
conf.d directories are loaded after the settings in the my.cnf file, they override the
settings in the main my.cnf file. This can be a good thing if that is what we want and
expect. Conversely, it can be a bad thing if we are not expecting that behavior. So
keep it in mind.
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The MariaDB configuration file
On Windows, the MariaDB configuration file is named my.ini by default and is
found in the data directory (see the Filesystem layout for Windows section to find
out the data directory's location). The file can also be named my.cnf just as it is on
Linux, and MariaDB will also look in the following additional locations for it:
C:\WINDOWS\my.ini
C:\WINDOWS\my.cnf
C:\my.ini
C:\my.cnf
On Linux, the MariaDB configuration file is always named my.cnf and is almost
always found at one of the following two locations:
/etc/my.cnf
/etc/mysql/my.cnf
MariaDB will look for the file at both locations, but if both files exist, the options
in the file MariaDB reads last will override the options it read in the first file. So to
avoid confusion, we should only have one or the other and if we discover we have
both for some reason, we should combine them into one file.
The configuration file is just a text file and we can edit it with our favorite text editor.
Even though the extensions may be different (.ini or .cnf) the contents of the files
are laid out the same. Apart from empty lines, which are ignored, there are four main
types of lines in a MariaDB configuration file. These are: comments, groups, options
with no values, and options with values.
Comments
Comment lines are lines that begin with # or ;. Comments are ignored by MariaDB.
They often contain useful information and are a great place to keep notes when we
make changes to the file. Comments can also start in the middle of the line. Just think
of anything from the initial comment character to the end of a line as a comment.
Here are some examples:
# Here is a comment
; This is also a comment
port = 3306 # Here's a comment about the port number
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Groups
Groups are sections in the configuration file. Each MariaDB program or utility can
have its own configuration information in it. Even individual series of MariaDB
have their own group (these are useful if we are testing a development version
and want to enable a new feature without affecting older servers that use the same
configuration file).
A group begins with the name of the group, enclosed in brackets ([]) on a line by
itself. The group continues to the end of the file or to the beginning of the next group.
Here is an example:
[mysqld]
# Configuration options for the mysqld program go here
In addition to [mysqld], other common groups include:
[mysql]
# configuration
[client-server]
# configuration
[mysqladmin]
# configuration
[mysqlcheck]
# configuration
[mariadb-10.0]
# configuration
options for the mysql command-line client
options for both clients and the server
options for the mysqladmin program
options for the mysqlcheck utility
options just for MariaDB 10.0 series servers
There are many other possible groups, but I think we get the picture. We just use the
ones we want and can ignore the others.
Options which do not require values
Configuration options either take a value or not. Those that do not need a value
appear on a line by themselves with no equals sign (=). They are used for options that
are either on or off so there is no need for arguments. If it exists in the configuration
file (and isn't commented out) the feature is on. If it doesn't exist (or it is commented
out) the feature is set to whatever the default is (ON or OFF). An example would be:
no-auto-rehash
To turn OFF a feature that is ON by default, just add =OFF to it as follows:
no-auto-rehash=OFF
We can also be more explicit about turning a feature on by appending =ON to an
option. It's not necessary though.
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One other thing worth noting is that option names are not case sensitive. We can also
choose to use dashes (-) or underscores (_) in the names. For example, the following
two options are the same:
• max_allowed_packet = 1M
• MAX-Allowed-Packet = 1M
One exception to this is with options that have values (described in the Options
which require values section). If the value is a file or location on a case-sensitive
filesystem like those used on Linux, that value will be case sensitive. The option
name is not case sensitive, but the value is. For example, the first two of the following
three examples work the same but the third does not (and on Linux it will almost
assuredly not work):
socket = /var/run/mysqld/mysqld.sock
Socket = /var/run/mysqld/mysqld.sock
socket = /VAR/run/mysqld/mysqld.sock
To keep our my.cnf file readable it is best to keep option names lowercase, even
though MariaDB will accept upper or mixed case. It is advised to keep options in
lowercase, unless they need to be otherwise.
Options which require values
As mentioned in the previous section, some configuration options require a value of
some sort to be set. For example, the default [client] section in the Ubuntu version
of the MariaDB my.cnf file contains the following two options:
port = 3306
socket = /var/run/mysqld/mysqld.sock
Setting options such as port or socket, or any other setting which requires a value,
without giving a value, will cause an error and MariaDB may refuse to start.
There is also a special line at the end of Linux my.cnf files. It begins with an
exclamation point (!) and its purpose is to include the special conf.d or my.cnf.d
directories. Don't change or remove this line!
Downloading the example code
You can download the example code files for all Packt books you
have purchased from your account at http://www.packtpub.
com. If you purchased this book elsewhere, you can visit http://
www.packtpub.com and register to have the files e-mailed directly
to you.
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Configuring MariaDB
Options, options everywhere
Each individual program and utility included with MariaDB has its own set of
configuration options. Run one from the command line with --help and we'll
get a list of all the options the program has and what they are currently set to.
Run the command with --print-defaults and we'll see the values that we've set.
For example, here's the output of the mysql command-line client program on my
local machine:
shell> mysql --print-defaults
mysql would have been started with the following arguments:
--port=3306 --socket=/var/run/mysqld/mysqld.sock
If we want to see all of the default values for a command (what they would be if we
didn't have a config file), use --no-defaults --help --verbose. For example:
shell> mysqld --no-defaults --help --verbose
The list that gets printed by this command is quite long, so we won't show it here.
And it shows more information than just the default values of options. What we're
interested in for now is a table towards the end of the output that begins with:
Variables (--variable-name=value)
and boolean options {FALSE|TRUE}
Putting all of the above information into practice, I've created a fairly generic and
heavily commented example my.cnf file. It is available in the code bundle given
away with this book.
There isn't space here to go into detail on the many options available for configuring
MariaDB. If we want to learn more, a good place to start is in the Optimization and
Tuning section of the MariaDB Knowledge Base available at https://mariadb.com/
kb/en/optimization-and-tuning/.
Activating configuration changes
The last stop on our highlights tour of MariaDB configuration is how to activate
changes once we've made them. To do so, we need to reload or restart MariaDB.
On Windows, we perform the following command:
sc stop mysql
sc start mysql
These two commands assume that we set the service name to mysql (the default)
during installation. If we set it to a different name, we would specify that instead.
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Chapter 2
On Linux systems, we generally do the following (and we may need to preface it
with sudo):
/etc/init.d/mysql reload
Example my.cnf file
There's an awful lot of information in this chapter about file locations,
comments, options, groups, and so on. If you're anything like me, your
head is probably swimming, wondering how you're ever going to make
sense of it all. To see a big picture view of how everything works together
I've created an example my.cnf file with lots of comments to explain the
different parts and settings of a typical my.cnf file. You can download it
from the book's website.
Summary
That's it for our configuration highlights tour! The next chapter is on securing
MariaDB. After all, now that we know how to configure MariaDB to our liking, we
wouldn't want some nefarious character to mess things up, now would we? We'll
cover an easy way to secure our new installation of MariaDB, and go over basic
things we can do to keep our database secure.
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MariaDB Security
Bad things happen—accidentally and on purpose—and we want to protect our
MariaDB database against both. Threats come in many different forms and come
from many different places including—but not limited to—physical threats,
filesystem threats, network threats, and user threats.
You can think of the data in your database as being at the center of a set of rings as
illustrated by the following diagram:
The outermost ring is the Internet. This is the outside world. If we are running a
business this is where our customers are. It's also where many attacks originate.
The next two rings are our Internal Network and the Building where our MariaDB
database server is located. Internal corporate networks can span several buildings,
but if we're a small business or a hobbyist the network might just be a single building
or even a room or two inside a building or house. We need to be careful of the
security on our internal network as we are on the external Internet, especially since
more attacks come from inside networks than from the outside world.
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MariaDB Security
Physical security is also important. If an attacker can simply walk in and take the
server or computer our MariaDB database is present and walk out with it, none
of our network and other security measures will mean anything. It's trivial for an
attacker to gain access to our data if they have physical access to the machine.
The next ring is the Server on which MariaDB is running. Who can log in? Where
can they log in from? Who has administrative rights? Does it have monitoring and
backup systems in place so we can keep an eye on it? The answers to these questions
depend on factors that are out of the scope of this book. We should find out the
answers though.
For example, if you know that only three other people have login access to the server,
we could tighten up security to a level—such as requiring SSH keys to login—that
might be unacceptable on a server that has hundreds of users or is shared with other
departments. Knowing who are the administrators of the server is useful because
we want to know who to call if something goes wrong. It's the same for backup
and monitoring systems; we need to know where they are and how to access them
because if we don't they won't be of much use to us when a problem occurs.
Now we're inside the server and have come to the center of the rings — the MariaDB
database itself. If it looks like MariaDB is sitting right at the center of a bullseye,
that's because it is. Security starts here and there's no better time to secure our
MariaDB installation than right now. We'll begin by working our way from the
inside out.
Securing MariaDB in ten seconds
The first thing we need to do after we install MariaDB is to run the mysql_secure_
installation script. This useful script ships with MariaDB and its sole purpose
is to quickly and easily set up some basic security. To run it, open a command line
and enter:
mysql_secure_installation
The script will ask several questions. For nearly all of them, it's best to answer yes
(y). The only question we might want to answer no to is when the script asks us to
set a root user password. If we've already set a root password we can safely skip this
question (the script is helpful enough to tell us when it is safe).
The other questions include removing the test database, removing the default
anonymous user, and disallowing remote root user logins. The anonymous user and
test database are included in the default MariaDB installation for testing purposes,
but there's almost never a reason to keep them. We can always create a new test user
and database, or several, for our testing needs.
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Following is the output of a complete run of the script on a server running Fedora 18:
[dbart@fedora18-amd64 ~]$ mysql_secure_installation
NOTE: RUNNING ALL PARTS OF THIS SCRIPT IS RECOMMENDED FOR ALL MariaDB
SERVERS IN PRODUCTION USE! PLEASE READ EACH STEP CAREFULLY!
In order to log into MariaDB to secure it, we'll need the current
password for the root user. If you've just installed MariaDB, and
you haven't set the root password yet, the password will be blank,
so you should just press enter here.
Enter current password for root (enter for none):
OK, successfully used password, moving on...
Setting the root password ensures that nobody can log into the MariaDB
root user without the proper authorization.
Set root password? [Y/n] y
New password:
Re-enter new password:
Password updated successfully!
Reloading privilege tables..
... Success!
By default, a MariaDB installation has an anonymous user, allowing anyone
to log into MariaDB without having to have a user account created for
them. This is intended only for testing, and to make the installation
go a bit smoother. You should remove them before moving into a
production environment.
Remove anonymous users? [Y/n] y
... Success!
Normally, root should only be allowed to connect from 'localhost'. This
ensures that someone cannot guess at the root password from the network.
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Disallow root login remotely? [Y/n] y
... Success!
By default, MariaDB comes with a database named 'test' that anyone can
access. This is also intended only for testing, and should be removed
before moving into a production environment.
Remove test database and access to it? [Y/n] y
- Dropping test database...
... Success!
- Removing privileges on test database...
... Success!
Reloading the privilege tables will ensure that all changes made so far
will take effect immediately.
Reload privilege tables now? [Y/n] y
... Success!
Cleaning up...
All done! If you've completed all of the above steps, your MariaDB
installation should now be secure.
As the output of the script says, after running it, our MariaDB installation is now
secure. In fact, if we run it immediately after installing MariaDB the only user that
will now be able to connect is root, and it will only be able to do so while we are
logged in to or sitting in front of the actual computer MariaDB is running on. This
isn't very convenient and we don't want to give other users or applications the root
user password, so we'll eventually have to add users and open things up at least a
little. Chapter 4, MariaDB User Account Management, goes into this subject.
Connecting safely
Now that the root user has a password, it's up to us to make sure the password—and
the passwords of all other users we will inevitably create—stay secure. One of the
most important ways to do that is to always follow a good connection practice.
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When connecting to MariaDB as root, or any other user, we tell the mysql command
line client that we are connecting with a password by using the -p flag. When we do
so we can either specify the password right after the -p flag with no space between,
as shown in the following command line:
mysql -u root -pmypassword
Or we can just leave the -p flag by itself and the client will prompt us for the
password, as shown in the following command line:
mysql -u root -p
Enter password:
It is almost never a good idea to type our password on the command line. The reason
is because status and system logs may record the command. This is very useful for
determining who is connecting and when, but it can be very dangerous as it exposes
the password to anyone who can access the logs. By using just -p and then entering
the password when prompted, the password is not echoed to the screen and is not
logged or displayed.
A situation might arise if we want to create a script that connects to our MariaDB
database at certain times to do some housekeeping or other tasks. Naturally, we want
the user to have rights to only do the things that it needs to do and we want the user to
have a good password. Using the password prompt method will work if we use a tool
such as Expect on Linux, but that may not be available, or work, in all cases. So how do
we connect without exposing the password? The answer is option files.
Option files are just text files, and technically we can create one anywhere, but it
should probably be in a logical location, like in the same folder that the script is in or
in a hidden directory in our home directory.
The contents of the option file can be any of the options we can put into a my.cnf file,
but for the preceding example of supplying a script with a username and password
the contents are very simple, only three lines, the first starting a client section and
the other two specifying the username and password to use (scriptuser and
scriptpassword in this example):
[client]
user = scriptuser
password=scriptpassword
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Notice that the preceding example uses spaces on the user line, but not on the
password line. This is because passwords can have spaces in them, so the MariaDB
mysql command-line client starts reading the password immediately after the equals
sign. So unless the first character of our password is a space, we start the password
immediately after the equals sign.
We tell the client to read the file by using the --defaults-file option, as follows:
mysql --defaults-file=/path/to/my-file
With the preceding in place, the client will read the file as it connects and use the
username and password we supplied (along with any other client options that we
add in the file).
To be safe when using this method, we should set the file so that it is readable
only by the user that will run the script. We can consult our operating system
documentation for the specifics on how to do this. On Linux-based systems a good
command to use is:
chmod 600 my-file
The preceding command sets the file as readable and writable by the user that
owns the file (6) and no access for everyone else (the two zeroes). Consult the chmod
documentation for full details.
On Windows, we can accomplish the same thing by right-clicking on the file in the
file manager, selecting Properties and then adjusting the access permissions. Consult
the Windows documentation for full instructions.
Server security
With MariaDB itself locked down nice and tight, and with us using good password
practices, we now need to look at the computer MariaDB is running on.
If we are running MariaDB on our own desktop or laptop, and we are the only one
who can log in to it, then there's not much to worry about apart from the normal
things we do to keep our computer secure—virus and malware protection, system
updates, keeping it in a secure location, and so on. It is also useful to encrypt our
hard drives, or at least our home folders using an operation supported by most
modern operating systems.
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When we install MariaDB on a dedicated server then there is more that we have to
worry about. Servers are almost always multiuser, so as part of server security, we
need to know who can log in and most importantly, who has root or administrator
access. If we are the administrator of the machine, we can ensure that only those we
want to have access to the administrator or root have access. If we're using MariaDB
on a machine that our I. T. department gave us access to then we need to find out
who has access and what their rights are, if for no other reason so that we know who
has sufficient rights on the server to make changes that could be harmful.
Building security
We come to building security by continuing out to the next ring. All the protection
inside the server won't do us any good if the server decides to take a walk at three
in the morning. Just as we secure the inside of the server, we need to secure the
outside too.
Firstly, where is the server located? Is it in a common area where anyone in the office
could get to it? This could be bad on a number of levels, the first being that someone
could accidentally or on purpose cut power to it. We can mitigate external power
outages to some extent by installing battery backup units and such, but someone with
physical access to the machine can easily get around that and cut power to our servers.
To its credit, MariaDB—when we use a transactional or crash safe storage engine—
guards against losing or corrupting data in such cases, but at the very least, a surprise
power outage will disrupt every application that needs to talk to that database server.
If the server is in a locked room, we should find out who has access to the room.
Also consider the building. Most businesses and offices close at night—the building
or office is locked at closing time and opens again in the morning—however this is
not true for all businesses. For example, what if the server is located in the manager's
office of a 24x7 supermarket and the door to that office is always open or unlocked?
If so then we need to think about locking that door (automatically if people keep
forgetting to lock it), or getting a small lockable server cage installed which is bolted
to the wall or floor, or come up with some other way of securing the server.
An easy analogy is to treat a server like money. We use database servers to either save
money, generate income, or both, so the analogy is apt. If we would feel comfortable
leaving a large stack of money in the location our server is in, then it is probably a
pretty good place for our server (assuming there is power and adequate cooling).
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The best place for a server is usually with other servers in a dedicated server room.
Preferably it should be a room that is secure and where access is controlled with
well-defined security policies and procedures. These could range from a locked
closet (that only a few chosen people can access and which has a the server sitting on
a shelf) to a locked server cage at a large data center (that has a raised floor cooling,
24x7 on-site security, and everything in surplus). There is no one particular location
that is right for every situation, but we need to evaluate ours and make sure our
server is physically protected.
Internal network security
The security of the internal network is related to building security. If our MariaDB
server is located in a locked server closet, then we will likely be accessing it remotely
from our desk. If so, then we need to at least be aware of the security of our internal
network. Some key questions to ask our local network administrator include:
• Is there a firewall in place to prevent outside access to our network?
°°
If there is, great! If not, suggest that one be added.
• Is there a Wi-Fi network that is directly connected to our internal network, or
is the Wi-Fi sectioned off into its own network?
°°
If the Wi-Fi network is connected directly to the internal network, see
if that can be changed.
• What type of access, if any, do telecommuting employees have—VPN, SSH,
something else?
°°
If telecommuting employees are forced into using VPN or SSH to
connect, that is good, as both of those access methods are encrypted.
If the answer is something else, we need to find out if it is secure and
encrypted (if it isn't, we need to complain).
°°
Are our database users defined with % for the network part or
are they all restricted to localhost or known valid locations and
networks? The % character is the wildcard character and its presence
in the network part of a username means that the user named can
connect from anywhere, which may be convenient, but is not good
from a security standpoint.
• If we are in a large company, do different departments have their own
segregated networks, and if so do they have access to the network the
server is on?
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• If our database is part of a project inside the company for a product in the
early stages of development, we might not want the salespeople, for example,
finding out about it until it is ready.
• At the very least, when we connect to the server remotely, we must always
do so securely using SSH or an encrypted tunnel. And if we don't know how
to do so we need to learn right away.
Internet security
The last ring is the outside world, that is, the Internet. Generally speaking, we don't
want to expose our MariaDB database server directly to the Internet ever. It's not that
MariaDB is especially vulnerable, any more than any other piece of software, it's just
that it's almost never necessary to expose it to the Internet and part of good security
is to not expose something unless we have to (in the same way that a poker player
doesn't want to reveal his hand to the other players, or the rest of the world). When
MariaDB is running on a web server, the web server software can directly connect with
no need for a network connection. If our MariaDB server is separate from our web
server, then we can almost always connect the two of them together over our internal
network and if not, we can set up some sort of secure tunnel between the two.
If you do think you've found a legitimate reason to expose your
MariaDB server to the entire Internet, I strongly encourage you to talk
with one of the many fine MariaDB consulting companies and have
them help you work out an alternative solution.
Summary
In this chapter, we learned a bit about how to secure our MariaDB server. Security is
a big topic, and cannot possibly be covered completely in a single chapter. There are
many resources, both online and offline, to help you learn more about this important
topic. But don't limit yourself to books or articles about securing MariaDB or other
databases; also take the time to learn about system, network, and physical security.
That said, the most secure safe in the world is one with no doors, windows, or other
openings of any kind, but it's not a very useful or safe if you can't access it when
you need to. So in the next chapter, MariaDB User Account Management, we'll make
our currently secure MariaDB server a bit more useful by adding user accounts and
learning how to manage them.
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MariaDB User Account
Management
The root user in our MariaDB database has rights to every database and table, we
don't want to use it for day-to-day operations or hand out the login ID and password
of root to anyone who doesn't absolutely need to have it. Instead, we want to create
users that have specific rights to the specific databases they need to work with.
User privileges
The privileges or rights that we can grant to users are many and varied. They break
down into three main categories:
• Global administrative privileges
• Database, table, and column privileges
• Miscellaneous privileges
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Global administrative privileges
The following table lists the global administrative privileges. Global privileges
apply to all databases and tables within those databases, which belong to the entire
MariaDB database server.
Privilege
CREATE USER
Description
The ability to create a user using the CREATE
USER statement.
FILE
The ability to use the LOAD DATA INFILE
statement and the LOAD_FILE() function.
PROCESS
The ability to use the SHOW PROCESSLIST
command.
RELOAD
The ability to use the FLUSH statement.
REPLICATION CLIENT
The ability to use the SHOW MASTER STATUS
and SHOW SLAVE STATUS commands.
REPLICATION SLAVE
The ability to get updates made on the
replication master server.
SHOW DATABASES
The ability to list all of the databases on the
server.
SHUTDOWN
The ability to shut down the server using the
mysqladmin shutdown command.
SUPER
The ability to use superuser statements such
as CHANGE MASTER TO..., PURGE LOGS; to
SET global variables; and to KILL other users'
threads.
Database, table, and column privileges
The following table lists the database and table privileges. These privileges only
apply to a specific database or table within a database.
Privilege
ALTER
Description
ALTER ROUTINE
The ability to change or delete procedures
and stored functions.
CREATE
The ability to create databases and tables.
CREATE ROUTINE
The ability to create procedures and
stored functions.
CREATE TEMPORARY TABLES
The ability to crate temporary tables.
The ability to change indexes and tables.
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Privilege
CREATE VIEW
Description
DELETE
The ability to delete rows from tables.
DROP
The ability to delete entire databases and
tables.
EVENT
The ability to alter, create, and drop
events from the event scheduler.
EXECUTE
The ability to execute stored functions
and procedures.
INDEX
The ability to create or delete indexes.
INSERT
The ability to insert new rows of data into
a table.
LOCK TABLES
The ability to lock and unlock tables.
SELECT
The ability to read data from a table.
SHOW VIEW
The ability to use the SHOW CREATE
VIEW statement.
TRIGGER
The ability to use the CREATE TRIGGER
and DROP TRIGGER statements.
UPDATE
The ability to modify rows in a table.
The ability to create views.
Column privileges apply to individual columns within a table. There are only three
of them: INSERT, UPDATE, and SELECT.
Miscellaneous privileges and limits
The following table lists miscellaneous privileges which don't quite fit into either of
the two previous categories.
Privilege
USAGE
Description
ALL PRIVILEGES
Can be used to grant all available privileges to a
user. Does not grant the GRANT OPTION privilege.
Can be shortened to ALL.
GRANT OPTION
Gives a user the ability to give other users the
privileges they have. This is given at the end of
the GRANT statement. See the Granting Permissions
section of this chapter for some examples.
Grants nothing real, but can be used to change
global options for a user.
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There are also several limits we can place on user accounts. These are given in
the following:
Limit
MAX_QUERIES_PER_HOUR
Description
MAX_UPDATES_PER_HOUR
The number of SQL update statements
(not queries) the user account can issue
per hour.
MAX_CONNECTIONS_PER_HOUR
The number of connections the user
account can start per hour.
MAX_USER_CONNECTIONS
The number of simultaneous connections
to the database server the user account
can have. If set to zero, the number will be
equal to the max_connections setting.
If the max_connections setting is also
zero then there is no limit to the number
of simultaneous connections.
The number of SQL statements or queries
the user account can issue per hour. This
includes updates.
Full documentation of the various privileges can be found at https://mariadb.
com/kb/en/grant/.
Creating users
Creating a user in MariaDB is a two-step process. First, we create the user using the
CREATE USER statement, and then we give, or GRANT, the user the privileges we want
them to have. We'll go over the CREATE USER statement in this section and the GRANT
statement in the Granting permissions section.
A CREATE USER statement has the following pattern:
CREATE USER 'username'@'host' IDENTIFIED BY 'password';
We customize the username, host, and password parts to the appropriate values.
If we don't want to specify a password (not recommended!) then we can drop the
IDENTIFIED BY 'password' part. This and all SQL statements that we input into
MariaDB need to end with a semicolon (;).
The host part can be several things. It can be the hostname of the computer the user
connects from, the IP address of the computer the user connects from, the network
the user connects from, or it can be the wildcard symbol %, which means any host.
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Here are some examples. This first example user can login from anywhere because of
the wildcard character, %, in the host part. The user's password is: bomber.
CREATE USER 'boyd'@'%' IDENTIFIED BY 'bomber';
The following three examples demonstrate using various host names. The first
specifies the localhost on which means the local server MariaDB is running. The
next specifies a single host. The third uses % to specify any subdomain of the
example.net domain.
CREATE USER 'tom'@'localhost' IDENTIFIED BY 'retail';
CREATE USER 'richard'@'powr.example.net' IDENTIFIED BY 'nuclear';
CREATE USER 'robert'@'%.example.net' IDENTIFIED BY 'pilot';
Instead of hostnames we can also use IP addresses as shown in the following three
examples. The first has an exact IP address identifying a single computer. The second
uses a % sign in the last quad of the IP address so any computer where the first three
sets of numbers in the IP address match will be able to connect. The third uses a
subnet mask, but the end result (in this example at least) is the same as the second.
CREATE USER 'dallin'@'192.168.1.1' IDENTIFIED BY 'judge';
CREATE USER 'russell'@'192.168.1.%' IDENTIFIED BY 'surgeon';
CREATE USER 'russell'@'192.168.1.0/255.255.255.0' IDENTIFIED BY
'business';
One benefit to using IP addresses instead of domain names is that no name
resolution or domain validation needs to be made. Such system calls to lookup
and check the validity of domains can be costly and might take time and resources
better spent on other things. To enforce a no domain names policy, add skip-nameresolv=1 to the [mysqld] section of the my.cnf or my.ini file.
Complete documentation of the CREATE USER statement is available at
https://mariadb.com/kb/en/create-user/.
Granting permissions
By default, new users do not have permission to do anything except logging
in, which is not very useful. So the next thing we need to do is give them the
permissions they need. This is done using the GRANT statement. Using this statement,
we will be able to GRANT users the appropriate permissions. The GRANT statements
have the following basic pattern:
GRANT <privileges> ON <database> TO <user>;
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We customize the <privileges>, <database>, and <user> parts as needed. The
<user> section should match the 'username'@'host' part of the CREATE statement,
otherwise, we'll be creating what is essentially a new user. We can also add an
IDENTIFIED BY 'password' section to the end of the GRANT statement if we want to
change the password (or add a password to an account that doesn't have one).
Here are some examples. This first one grants all privileges including the grant
option on all databases and the user can log in from anywhere. We should not often
set up users with such broad authority, and when we do we need to make sure, we
use an appropriate CREATE USER statement first and assign the user a password
(or assign the password here). If the user doesn't exist, the GRANT statement will
create one, but if the user doesn't exist and our GRANT statement doesn't include
an IDENTIFIED BY 'password' section then the user will be created without a
password, so it's a good habit to first create the user with a password, and then grant
the user the rights they need.
GRANT ALL ON *.* TO 'robert'@'%' WITH GRANT OPTION;
The following example is a standard set of permissions for a regular user who needs
read and write access to a database called serv. If a user just needs read access, we
can just assign the user the SELECT privilege. By specifying serv.* as the database,
the user only has these rights on tables in the serv database. Multiple privileges are
separated by commas.
GRANT SELECT,INSERT,UPDATE,DELETE ON serv.* TO 'jeffrey'@'localhost';
This following user has read access (SELECT) to just the staff table in the edu
database, and the user has the GRANT OPTION privilege so they can grant that same
right to other users.
GRANT SELECT ON edu.staff TO 'david'@'localhost' WITH GRANT OPTION;
The following example gives a user all rights on the logan database. We'll also limit
this user to 100 queries per hour, just because we can.
GRANT ALL ON logan.* TO 'quentin'@'localhost' WITH MAX_QUERIES_PER_HOUR
100;
Complete documentation of the GRANT statement is available at
https://mariadb.com/kb/en/grant/.
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Adding and removing privileges
Sometimes it becomes necessary to remove a privilege or two from a user, or to give
them more privileges. Giving additional privileges is easy, just run an additional
GRANT statement with the new rights and they will be added. To remove privileges,
we use the REVOKE statement. It has the following pattern:
REVOKE <privileges> ON <database> FROM <user>;
To remove a GRANT OPTION privilege, specify it in the privileges section. The
following example removes the DELETE and GRANT OPTION permissions from the
todd user:
REVOKE DELETE,GRANT OPTION ON cust.* FROM 'todd'@'%';
To remove all privileges from a user ('neil'@'%.example.com' in this example), we
use the following special command:
REVOKE ALL,GRANT OPTION FROM 'neil'@'%.example.com';
We, of course, need to customize the user part to match the user for whom we are
removing privileges. The previous statement is special in that it must be used as
written even if the user doesn't have the GRANT OPTION privilege. If we remove the
GRANT OPTION privilege from it the statement won't run.
Complete documentation of the REVOKE statement is available at: https://mariadb.
com/kb/en/revoke/.
Showing grants
To show the grants available for a user, we use the SHOW GRANTS command. It has
the following pattern:
SHOW GRANTS FOR <user>;
All we have to do is customize the <user> part with the information of the user we
want to look at. Here is an example:
SHOW GRANTS FOR 'dieter'@'10.2.200.4';
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The output of the SHOW GRANTS command is a GRANT statement that encapsulates all
of the user's privileges. This is useful if you want to give another user the exact same
privileges. For example, the output of the preceding SHOW GRANTS command might
be as follows:
+------------------------------------------------------+
| Grants for dieter@10.2.200.4
|
+------------------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO 'dieter'@'10.2.200.4' |
+------------------------------------------------------+
Changing passwords
To change the password of a user, we use the SET PASSWORD statement. It has the
following pattern:
SET PASSWORD FOR <user> = PASSWORD('<password>');
Here is an example:
SET PASSWORD FOR 'henry'@'%' = PASSWORD('niftypassword');
Complete documentation of the SET PASSWORD statement is available at
https://mariadb.com/kb/en/set-password/.
Removing users
To remove a user completely, we use the DROP USER statement. It has the
following pattern:
DROP USER <user>;
Here is an example:
DROP USER 'tom'@'%';
When a user is dropped, all grants are automatically removed.
Complete documentation of the DROP USER statement is available at
https://mariadb.com/kb/en/drop-user/.
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Summary
In this chapter, we learned about adding and removing users and how to give those
users the permissions they need or take them away as needed. Up till now, we've
only talked about things related to our databases (securing them, managing users,
and so on). We haven't actually done anything with the actual data—you know the
stuff that databases are good at storing and retrieving. Well, the time to talk about it
is now. In the next chapter, Using MariaDB, we'll learn some basic SQL commands
that we can use with the mysql command-line client program to create databases,
insert data, read data, and so on.
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This chapter will focus on using the command-line mysql client to perform common
tasks. We'll learn about creating and dropping databases and tables, making
modifications to our tables, inserting and updating data, viewing the results, and
more. When finished we will have a good grasp of the basics. We'll know our way
around, a skill which is always useful, even if we end up spending most of our time
using graphical point-and-click clients, or applications that interact with the database
for us.
Running the mysql command-line client
A big part of becoming a MariaDB expert is learning how to effectively and
efficiently use the command-line mysql client program. Many MariaDB users interact
with the server using custom programs that have been developed specifically for
or by them. At a lower level though, every interaction these applications have with
MariaDB can be done with the command-line client.
MariaDB has a client-server architecture, which means there are two parts to it: the
server, which is the part that does the heavy behind-the-scenes stuff, and the client,
which is the part we use to access and interact with the server. We hardly ever
interact directly with the server part. There are many different clients for MariaDB,
but only one is maintained by the MariaDB developers and included with every copy
of MariaDB—the mysql command-line client.
To start the client, we open up a command-line or terminal window and type mysql
with some options and press Enter. The basic syntax is as follows:
mysql [-u <user>] [-p] [-h <host>] [<database>]
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All of the options in the previous example are in brackets ([]) to show that they are all
optional. The parts in angle brackets (<>) are bits that we must supply if we choose to
use that option. For example, if we use the -u option, we must supply a username.
Most of the time, we will use the user (-u) and password (-p) options. We will also
often specify the database that we want to connect to when the client launches. When
we connect remotely to a MariaDB server on another computer, we will use the host
(-h) option.
A successful connection will look similar to the following:
daniel@gandalf ~ $ mysql -u root -p
Enter password:
Welcome to the MariaDB monitor. Commands end with ; or \g.
Your MariaDB connection id is 31
Server version: 5.5.30-MariaDB-mariadb1~quantal-log mariadb.org binary
distribution
Copyright (c) 2000, 2013, Oracle, Monty Program Ab and others.
Type 'help;' or '\h' for help. Type '\c' to clear the current input
statement.
MariaDB [(none)]>
The last line of the output, MariaDB [(none)]>, is the MariaDB prompt. It appears
whenever MariaDB is waiting for us to give it a command. Apart from its primary
purpose, the prompt gives us two pieces of very useful information. First, the
prompt says MariaDB which tells us that we are connecting to an actual MariaDB
database server (as opposed to a compatible database server that isn't actually
MariaDB). Second, the part in brackets tells us which database on the server we are
currently using; in this case, we aren't using any database, so it says (none).
Using a database
We generally want to be connected to a specific database when we use the commandline client. To use a database, we either specify it on the command-line when
launching the client as shown in the previous section, or we use the USE command,
to tell the client which database we want to talk to. The following example illustrates
connecting to a database named test. Notice that the prompt changes to let us know
the name of the database it is currently connected to.
MariaDB [(none)]> USE test;
Database changed
MariaDB [test]>
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If the database does not exist when we try to USE it, we will get the following error.
MariaDB [(none)]> use test1;
ERROR 1049 (42000): Unknown database 'test1'
Listing all databases on a server
To show a list of all of the databases on a server, use the SHOW DATABASES command
as in the following example:
MariaDB [(none)]> SHOW DATABASES;
+--------------------+
| Database
|
+--------------------+
| information_schema |
| dbt3_s001
|
| flightstats
|
| mysql
|
| performance_schema |
| test
|
+--------------------+
6 rows in set (0.00 sec)
MariaDB [(none)]>
You may have noticed in the previous examples that all the commands
ended with a semi-colon (;). This is called the delimiter and it is a
characteristic feature of Structured Query Language (SQL). We interact
with the command-line client using this language. In basic terms, SQL is
a computer language optimized for interacting with a database. MariaDB
uses its own variant of SQL which is similar to but not exactly the same
as the SQL variants used by other databases. When we learn how to write
SQL statements for MariaDB, we also learn a good deal about writing
SQL for other databases, but there are some differences. For instance, USE
and SHOW are commands, which exist in MariaDB but not in some other
databases that use their own variety of SQL.
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Creating and dropping databases
When we install MariaDB, we're installing a database server, not a specific database,
and a single MariaDB database server can have several databases inside it. Here's an
analogy that can help us understand this arrangement: a database can be thought of as
a large filing cabinet. The filing cabinet contains a number of drawers and inside each
drawer are files with information. In this analogy, the filing cabinet is a database, the
drawers are tables within the database, and the files are rows of data within the tables.
So what is MariaDB? It's the room the filing cabinet is located in, and it's a large room
so we can put many filing cabinets inside it. When MariaDB is installed, the installer
creates a system database that MariaDB uses to keep track of users and databases
and other housekeeping information. The installer also creates a test database for
experimentation and learning and a read-only database where MariaDB stores
performance statistics. We don't want to use the system database as we could mess up
the entire server if we made a mistake. We can't put data into the statistics database,
called performance_schema, because it is read only. We can use the test database,
but we probably don't want to use it for anything permanent. So one of our first tasks
when we start using MariaDB is to create at least one database for us to use.
Generally, databases are created for specific things or specific applications. For
example, we could have an accounting database for the finance department, a human
resources database for the HR department, and a parts database for the warehouse.
Creating and dropping (deleting) databases are two things that we will do less often
than just about anything else when working with MariaDB. There just isn't much
call for it in day-to-day work. We generally create a database and then use it as long
as it is needed (which could be for years or decades) and then we delete (drop) it.
Thankfully, the commands for creating and dropping a database are very simple, so
they're easy to remember.
Creating a database
As mentioned previously, creating a database is not something we do often. To
create a database in MariaDB, we use the CREATE DATABASE command. The basic
syntax is as follows:
CREATE DATABASE <databasename>;
If the database already exists when we try to create it, we will receive an error. We
can suppress the error with IF NOT EXISTS.
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Here are some examples:
CREATE DATABASE my_database;
CREATE DATABASE IF NOT EXISTS my_database;
The previous two commands are equivalent if the database does not exist. If the
database does exist, the first command will exit with an error and the second
command will do nothing.
Full documentation of the CREATE DATABASE command is available at
https://mariadb.com/kb/en/create-database/.
Dropping a database
As mentioned before, it isn't often that we need to remove or delete a database, but
when we do, we use the DROP command. The basic syntax is as follows:
DROP DATABASE <databasename>;
If the named database doesn't exist when we try to drop it, we will receive an error.
We can suppress the error with IF EXISTS.
Here are a couple of examples that drop the database we just created:
DROP DATABASE my_database;
DROP DATABASE IF EXISTS my_database;
The preceding two commands are equivalent if the database my_database exists. If
the database does not exist, the first command will exit with an error and the second
command will do nothing.
When dropping a database, user privileges for the database are
not removed. We need to revoke them manually, or drop the user
entirely; otherwise, if or when the database is recreated the user will
still have the privileges. See Chapter 4, User Account Management, for
information on managing users and their privileges.
Complete documentation of the DROP DATABASE command is available at
https://mariadb.com/kb/en/drop-database/.
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Creating, altering, and dropping tables
Databases contain tables. Tables are two-dimensional data structures containing
rows and columns. A row corresponds to a single record in a database and records
are divided into columns. Think of database tables like a specialized spreadsheet.
The many multiple tables in a MariaDB database have columns, which can relate in
one way or another. For example, the id column in an employee table may relate to
the employee_id column in an address table. These relationships (also called foreign
keys) are why we call MariaDB a relational database.
A database without tables of data is nothing more than a name. Until we create some
tables and start adding data to those tables, our database is empty and useless.
Creating a table
There are few things in MariaDB we will spend more time on, at least in the
beginning than when we do creating or defining the tables for our database.
We use the CREATE TABLE command to create tables. Using the command, we
define the structure of the table. The structure includes such things as the number
of columns and the type of data that we want to store in each column. Datatypes
include things such as numbers, text, and dates. For example, if we are creating an
employee table, we might decide to store an employee ID number (number), last
name (text), given names (text), preferred name (text), birthdate (date), and so on.
We might also want to store the e-mail addresses, phone numbers, and home
addresses of the employees, but we don't want to store duplicate data, or define extra
columns that are hardly ever used, so we should put those in separate tables and
then link the records back to the appropriate employee. We do this because people
often have multiple phone numbers and e-mail addresses, and sometimes even extra
home addresses and we might want to store all of them.
The process by which we refine our table definitions is called normalization.
There isn't space here for a complete discussion of this process, but the MariaDB
Knowledge Base has a page which discusses it in depth available at https://
mariadb.com/kb/en/recap-the-relational-model.
For a basic database for an online store, we might have tables for customers,
products, orders, product reviews, customer addresses, and more. We can create as
many tables as we need, but as mentioned previously, we should give the design
some thought so that we don't store duplicate or unused data. That said, don't
worry too much, we can always make changes after the fact with the ALTER TABLE
command (see the Altering a table section in this chapter).
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The basic syntax of the CREATE TABLE command is as follows:
CREATE TABLE table_name (<column_definitions>);
As with creating a database, we can add an IF NOT EXISTS command before the
table name to suppress the error that would appear if the table exists when we try
to create it.
The <column_definitions> part has the following basic pattern:
<column_name> <data_type>
[NOT NULL | NULL]
[DEFAULT <default_value>]
[AUTO_INCREMENT]
[UNIQUE [KEY] | [PRIMARY] KEY]
[COMMENT '<string>']
The parts in angle brackets (<>) are the bits that we fill in. The parts in square
brackets ([]) are optional and the pipe character (|) means or. For example, we can
(but do not have to) specify NULL or NOT NULL in a single column definition but we
cannot specify both. Columns are allowed to be NULL, or have no value, by default.
Marking a column as NOT NULL means it can never be empty; some value has to be
assigned to it. Multiple column definitions are separated by commas.
There are many different datatypes (<data_type>) to choose from. A datatype
(<data_type>)is a type of data being stored. They exist because each is efficiently
stored somewhat differently. Plain numbers can be treated differently than dates
and vise versa. Common ones include numeric, string, and date datatypes. Numeric
datatypes include INTEGER (commonly written as INT), and FLOAT (for floating point
numbers). String (or text-based) datatypes include CHAR, TEXT, and VARCHAR. Lastly,
date and time datatypes include DATE, TIME, and DATETIME.
See a complete list of supported datatypes at https://mariadb.com/kb/en/data-
types/.
Don't worry about trying to memorize all of the different datatypes now.
They'll become second nature as we gain experience using MariaDB.
After specifying the type, length, and precision (for some datatypes), we specify other
options. We can specify whether or not the column is allowed to be empty (or NULL),
what the default value (<default_value>) is, if anything, whether the column autoincrements (only for numeric datatypes), whether the value in the column should be
UNIQUE, whether the column is a primary key, and a comment, if desired.
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A primary key is a column or group of columns, which uniquely identifies a specific
row in the table. No other row in a given table is allowed to have the same primary
key. If we try to input a row with a primary key that matches another primary key in
the table we will get an error.
For our preceding employees example, we might use the following CREATE
statement to create the table (use the test database or CREATE a new database
and then USE it if you want to follow along):
CREATE TABLE employees (
id INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
surname VARCHAR(100),
givenname VARCHAR(100),
pref_name VARCHAR(50),
birthday DATE
);
When we run the preceding code, the output looks like this:
Query OK, 0 rows affected (0.00 sec)
A result of Query OK means that the table was created successfully. Zero rows
were affected because this brand new table has no data in it yet.
Full documentation of the CREATE TABLE command can be found at
https://mariadb.com/kb/en/create-table/.
Showing the command used to create a table
At any time, for example, if we want to create a similar table in a different database,
we can use the SHOW CREATE TABLE command to show a command that will recreate
the table exactly. Here is an example:
MariaDB [test]> SHOW CREATE TABLE employees\G
*************************** 1. row ***************************
Table: employees
Create Table: CREATE TABLE `employees` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`surname` varchar(100) DEFAULT NULL,
`givenname` varchar(100) DEFAULT NULL,
`pref_name` varchar(50) DEFAULT NULL,
`birthday` date DEFAULT NULL,
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PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1
1 row in set (0.00 sec)
The \G at the end of the command in this example is an alternative
to using a semicolon (;) and when used it presents the output in a
slightly different way which works well for this example.
The actual CREATE TABLE command that is displayed is slightly different from the
CREATE TABLE command that we used to create it, but the table created is exactly
the same. The differences exist because MariaDB is giving us enough information to
recreate the table exactly, even if we're creating it on a different server with different
defaults.
For example, the ENGINE and DEFAULT CHARSET parts after the column definitions
are default table options on this MariaDB Server. Here they are specified because on
a different MariaDB server the defaults may be different.
Full documentation of the SHOW CREATE TABLE command can be found at
https://mariadb.com/kb/en/show-create-table/.
Exploring the structure of a table
If we don't necessarily want to look at the commands used to create a table but we
want to know the structure of a table, we can use the DESCRIBE command as follows:
MariaDB [test]> DESCRIBE employees;
+-----------+--------------+------+-----+---------+----------------+
| Field
| Type
| Null | Key | Default | Extra
|
+-----------+--------------+------+-----+---------+----------------+
| id
| int(11)
| surname
| PRI | NULL
| auto_increment |
| varchar(100) | YES
|
| NULL
|
|
| givenname | varchar(100) | YES
|
| NULL
|
|
| pref_name | varchar(50)
| YES
|
| NULL
|
|
| birthday
| YES
|
| NULL
|
|
| date
| NO
+-----------+--------------+------+-----+---------+----------------+
5 rows in set (0.03 sec)
Full documentation of the DESCRIBE command can be found at https://mariadb.
com/kb/en/describe/.
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Altering a table
We can spend hours, days, and even weeks getting our tables defined just the way
we want them, but chances are at some point we'll need to make some changes. This
is where the ALTER TABLE command comes into play.
The basic syntax for the ALTER TABLE command is as follows:
ALTER TABLE table_name <alter_definition>[, alter_definition] ...;
An <alter_definition> command can ADD, MODIFY, and DROP (delete) columns
from tables, among other things. Multiple alter definitions in a single ALTER TABLE
command are separated by commas. Because we can have multiple alter definitions
in one ALTER TABLE command, the syntax examples in the next four sections will
not contain the beginning ALTER TABLE table_name part that must begin an ALTER
TABLE command. The examples that demonstrate actual usage will.
Adding a column
An <alter_definition> attribute of an ALTER TABLE command is used to add a
column has the following pattern:
ADD <column_name> <column_definition> [FIRST | AFTER <column_name>]
The FIRST and AFTER parts are optional. We can use one, but not both. The FIRST
option puts the new column as the first column of the row. The AFTER option lets us
specify, which column the new column appears after.
For example, the following will create a new username column and place it after the
pref_name column:
ALTER TABLE employees ADD username varchar(20) AFTER pref_name;
Modifying a column
An alter definition of an ALTER TABLE command to modify a column has the
following pattern:
MODIFY <column_name> <column_definition>
For example, the following ALTER TABLE command will change the pref_name
column to varchar(25):
ALTER TABLE employees MODIFY pref_name varchar(25);
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Dropping a column
An alter definition of an ALTER TABLE command to delete a column has the
following pattern:
DROP <column_name>
For example, the following ALTER TABLE command will delete the username column
we created earlier:
ALTER TABLE employees DROP username;
Full documentation of the ALTER TABLE command is found at https://mariadb.
com/kb/en/alter-table.
Dropping a table
When we no longer need a table, just as when we no longer need a database, we
drop it. Out of the table commands, this one is by far the easiest. The basic syntax of
the command is:
DROP TABLE <table_name>
If we try to drop a table that doesn't exist we will receive an error. We can suppress
the error with IF EXISTS.
Here are a couple of examples:
DROP TABLE mytable;
DROP TABLE IF EXISTS mytable;
If the table exists, the preceding two commands are equivalent. If the table doesn't exist
the first command will exit with an error and the second command with do nothing.
Full documentation of the DROP TABLE command can be found at
https://mariadb.com/kb/en/drop-table.
Selecting, inserting, updating, and
deleting data
Getting data into and out of our database tables and updating, and deleting data when
necessary is where we will spend most of our time when working with MariaDB.
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Inserting data
To put data into our database, we use the INSERT command. The basic syntax is
as follows:
INSERT [INTO] <table_name> [(<column_name>[, column_name,...])]
{VALUES | VALUE}
({expression|DEFAULT},...)[,(...),...];
As with the CREATE TABLE command, the parts in angle brackets (<>) are what we'll
replace with our own values. The square brackets ([]) are optional and the pipe
character (|) means or. The curly brackets ({}) specify a section that is mandatory
but for this there is a choice of the key word you can use. For example, the INTO
keyword is optional but makes the INSERT line more readable and we can use the
keyword VALUES or VALUE depending on whether or not we are inserting a column of
information or multiple items but we must use one of them. Anywhere when we see
three dots (...) it represents a part where the previous part can be repeated.
Expression just means the value we want to put in the column. It could be a
calculated value (such as today's date + four days), a static value (such as John) or it
could be the default value assigned to the column (if it has one). Default values are
assigned using the keyword DEFAULT without any quotes.
If we do not specify the columns we want to insert into, then we must specify a
value for each column. If we don't want to assign a value (and if the column
definition allows it) we can specify NULL, which means no value.
We can also insert multiple rows at once (remember to use the keyword VALUES
when doing so!). Each row is wrapped in parentheses and multiple rows are
separated by commas.
Following are some basic INSERT examples. They are split onto multiple lines to aid
reading but can be entered with a single long line if desired. Remember that a single
command ends with either the semicolon (;) or \G delimiters.
INSERT INTO employees (surname,givenname) VALUES
("Taylor","John"),
("Woodruff","Wilford"),
("Snow","Lorenzo");
INSERT INTO employees (pref_name,givenname,surname,birthday)
VALUES ("George","George Albert","Smith","1970-04-04");
INSERT employees (surname) VALUE ("McKay");
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INSERT INTO employees VALUES
(NULL, "Kimball", "Spencer", NULL, NULL);
Full documentation of the INSERT command is found at https://mariadb.com/kb/
en/insert/.
Updating data
When data in a table needs to be updated, we use the UPDATE command. The basic
syntax is as follows:
UPDATE <table_name>
SET column_name1={expression|DEFAULT}
[, column_name2={expression|DEFAULT}] …
[WHERE <where_conditions>];
Unlike the INSERT command, when we are updating data we specify the data we
want to insert right after each column name. Another difference is inclusion of a
WHERE section. The WHERE section is very important because we use it to specify
the exact column or columns of data in the table we want to change. If we omit the
WHERE section the UPDATE statements will update every instance of that column. For
example, we could accidentally change every employee's phone number to the same
number when all we wanted was to update Gordon's.
One thing we should do in our example employees table is add birthdays and
preferred names for some of our employees:
UPDATE employees SET
pref_name = "John", birthday = "1958-11-01"
WHERE surname = "Taylor" AND givenname = "John";
UPDATE employees SET
pref_name = "Will", birthday = "1957-03-01"
WHERE surname="Woodruff";
UPDATE employees SET
birthday = "1964-04-03"
WHERE surname = "Snow";
For each of the preceding commands, MariaDB should output the following two
lines (the amount of time, 0.03 seconds in the example, may be different):
Query OK, 1 row affected (0.03 sec)
Rows matched: 1
Changed: 1
Warnings: 0
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What these two lines are telling us is that one row matched our WHERE section and
that one row was changed.
Full documentation of the UPDATE command is found at https://mariadb.com/kb/
en/update/.
Deleting data
When data needs to be removed from a database table, we use the DELETE command.
The basic syntax is as follows:
DELETE FROM <table_name> [WHERE <where_conditions>];
As with UPDATE statements, the WHERE part of a DELETE statement is optional, but if
we leave it off, the command will delete every row in the table, which is even more
catastrophic than leaving off the WHERE part in an UPDATE statement, if such a thing is
possible, so make it a habit to always include it.
As an example, let's delete the Spencer Kimball employee:
DELETE FROM employees
WHERE givenname="Spencer" AND surname="Kimball";
Full documentation of the DELETE command is found at https://mariadb.com/kb/
en/delete/.
Reading data
The command for reading data from our database is called SELECT. Of all SQL
commands, this is the one we will probably use most often. As such the syntax is
rather complex, or can be, if we choose to use all the various options. The basic
syntax is as follows:
SELECT <what> FROM <table_name>
[WHERE <where-conditions>]
[ORDER BY <column_name>];
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A common <what> condition is to grab everything. This is done using an asterisk (*)
as follows:
MariaDB [test]> SELECT * FROM employees;
+----+----------+---------------+-----------+------------+
| id | surname
| givenname
| pref_name | birthday
|
+----+----------+---------------+-----------+------------+
| 1
| Taylor
| 2
| 3
| John
| John
| 1958-11-01 |
| Woodruff | Wilford
| Will
| 1957-03-01 |
| Snow
| Lorenzo
| NULL
| 1964-04-03 |
| 4
| Smith
| George Albert | George
| 1970-04-04 |
| 5
| McKay
| NULL
| NULL
| NULL
|
+----+----------+---------------+-----------+------------+
5 rows in set (0.00 sec)
However, when our table contains lots of columns, we probably will only want to
select certain of them. To do so we list the columns, separated by commas, in the
<what> section. For example, we could select just the preferred names and surnames
as follows:
MariaDB [test]> SELECT pref_name,surname FROM employees;
+-----------+----------+
| pref_name | surname
|
+-----------+----------+
| John
| Taylor
|
| Will
| Woodruff |
| NULL
| Snow
|
| George
| Smith
|
| NULL
| McKay
|
+-----------+----------+
5 rows in set (0.00 sec)
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Another thing we may want to do is select only certain rows, for example, everyone
born after 1 January, 1960:
MariaDB [test]> SELECT * FROM employees
-> WHERE birthday > '1960-01-01';
+----+---------+---------------+-----------+------------+
| id | surname | givenname
| pref_name | birthday
|
+----+---------+---------------+-----------+------------+
| 3
| Snow
| Lorenzo
| 4
| Smith
| George Albert | George
| NULL
| 1964-04-03 |
| 1970-04-04 |
+----+---------+---------------+-----------+------------+
2 rows in set (0.00 sec)
The > sign is a comparison operator. Just like in math, it means greater than.
There are many other comparison operators. See https://mariadb.com/kb/en/
comparison-operators/ for a complete list.
The arrow (->) in the previous output example is not something we
typed. The mysql command-line client program inserted it to show
that we pressed the Enter key before ending our command with a
semicolon (;), and so the command we are entering is continuing on a
second line. If we pressed Enter and just forgot to end our command,
we can just type a semicolon and press Enter again. In the previous
example, I did it on purpose to split the command onto two lines to
make it easier to read.
Our output, by default, is sorted based on the order in which it was inserted into the
database. For a list of employees we really should sort on the surname column. To
do this we use an ORDER BY clause as follows:
MariaDB [test]> SELECT * FROM employees ORDER BY surname;
+----+----------+---------------+-----------+------------+
| id | surname
| givenname
| pref_name | birthday
|
+----+----------+---------------+-----------+------------+
|
5 | McKay
| NULL
| NULL
| NULL
|
|
4 | Smith
| George Albert | George
| 1970-04-04 |
|
3 | Snow
| Lorenzo
| NULL
| 1964-04-03 |
|
1 | Taylor
| John
| John
| 1958-11-01 |
|
2 | Woodruff | Wilford
| Will
| 1957-03-01 |
+----+----------+---------------+-----------+------------+
5 rows in set (0.00 sec)
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We can set the order of any column the way we wish using ORDER BY, and even
specify multiple columns, separating each column with a comma just as we do in the
<what> section.
We can also use pattern matching to select rows when we only know some of the
information. For example, suppose we want to look up an employee whose name
begins with the letters McK but we don't remember the rest. We can look up this
employee using a WHERE clause as follows:
MariaDB [test]> SELECT * FROM employees
-> WHERE surname LIKE "McK%";
+----+---------+-----------+-----------+----------+
| id | surname | givenname | pref_name | birthday |
+----+---------+-----------+-----------+----------+
| 5
| McKay
| NULL
| NULL
| NULL
|
+----+---------+-----------+-----------+----------+
1 row in set (0.00 sec)
The percent sign (%) is what is known as a wildcard character. It matches zero or
more instances of any character or group of characters. So by specifying the surname
pattern McK%, we are saying that we want any surnames that begin with those letters
and are followed by zero or more other characters. This pattern would match items
such as McKay, McKinsey, McKool, and even McK.
Full documentation of the SELECT command is found at https://mariadb.com/kb/
en/select/.
The SELECT commands are even more powerful when we start using JOINS to gather
data from multiple tables. For example, if we had an address table along with our
employee table, we could SELECT the names and addresses of all employees who live
in a certain city and whose birthdays are less than a month away so that we can send
them a gift certificate to a restaurant in that city. Full documentation of JOIN syntax
is found at https://mariadb.com/kb/en/join/
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Summary
In this chapter, we learned some basic commands which are useful when using
MariaDB and connecting with the mysql command-line client program. We've also
become familiar with the basic SQL database Create, Read, Update, and Delete
(CRUD) operations that will be part of nearly all of our interactions in MariaDB.
In the next chapter, MariaDB Maintenance, we will learn how to keep our database
running smoothly.
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MariaDB Maintenance
Just like houses and cars, databases need to be maintained if they are to run
smoothly. In this chapter we'll cover a variety of maintenance-related topics. We'll
start with an exploration of the various MariaDB log files, which tell us what
MariaDB is doing. Then we'll move on to a discussion about optimizing MariaDB.
We'll then discuss what is probably the most important part of maintaining our
database: backups. Lastly, we'll cover the utilities MariaDB includes to repair tables.
MariaDB log files
Depending on how we configure it, MariaDB will keep very detailed or very sparse
logs. The location of these logs is configured in our my.cnf (my.ini on Windows)
MariaDB configuration file. On Linux, the default location is /var/log/mysql/ and
on Windows the default location is in the MariaDB data directory.
There are several different kinds of logs, each kind serving a different purpose.
The all-important binary log
The MariaDB binary log is a series of files that contain events. An event is a description
of a modification to the contents of our database. As indicated by the name, and unlike
most other kinds of log files, MariaDB binary log files are in a binary format. They are
not readable by us unless we use a helper program such as mysqlbinlog.
The binary log is controlled by the log_bin variable. The main purpose of the
variable is to turn binary logging on and off. Basically, if the variable is present in the
[mysqld] section of our config file, binary logging will be turned on, and if it isn't,
binary logging will be turned off. An optional function of this variable is to set the
name and location of the binary log. Here is an example:
log_bin = /var/log/mysql/mariadb-bin
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MariaDB will take the name and add numbers to the end of the actual files it writes
to. Here is an example of using the mysqlbinlog program to display the contents of
a binary log in human-readable text:
mysqlbinlog /var/log/mysql/mariadb-bin.000269
Each event in a binary log file is preceded with some comment lines that give the
date and time of the event and its position in the log.
Apart from its informational value, the MariaDB binary log has some other uses.
First, it can be used to recover after a server crash. It is also used when replicating
from one server to another. When used for replication, they are transferred to the
slave servers as relay logs, but they are basically the same as regular binary logs and
can be read with the mysqlbinlog program.
More information about the binary log can be found at https://mariadb.com/kb/
en/binary-log/.
The error log
The error log is where MariaDB logs information about critical errors. This is also
where MariaDB records startup and shutdown information. If MariaDB crashes or
fails to start, this is the log where we should look first.
We can control the location using the log_error variable, which, like other
logging variables, is placed in the [mysqld] section of our configuration files.
Here is an example:
log_error = /var/log/mysql/error.log
The default configuration files shipped with MariaDB on Linux configure this file to
be at this location, but it can be placed elsewhere.
Unlike the binary log, the absence of this variable does not turn error logging off.
If the location is not configured in our my.cnf or my.ini file, error logging is still
enabled and the default location is the data directory. Also, the default name will be
hostname.err where hostname is the name of the computer MariaDB is running on.
More information about the error log can be found at https://mariadb.com/kb/
en/error-log/.
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Chapter 6
The general query log
The general query log is disabled by default. This is because the general query log,
when enabled, stores a record of every query MariaDB receives, including queries
that don't change any data. This is in contrast to the binary log, which only stores
queries that change data. On a busy server with lots of users, storing all queries can
lead to lots of huge log files very quickly. It is not usually necessary or recommended
to enable this log.
However, if we are trying to discover a hidden performance bottleneck or absolutely
need a record of everything the server is doing, this log can be enabled with the
general_log and general_log_file variables. The first is used to explicitly turn
the general log on (=1) or off (=0). The second configures where we want the log to
be and what we want it to be called. Here is an example:
general_log = 1
general_log_file = /var/log/mysql/mysql.log
If we are only interested in queries which change data, the only log we need to look
at is the binary log and we do not need to enable the general query log. As it says
in a comment in the default my.cnf file shipped with MariaDB, the general log is
a performance killer, so we should only enable it if we need to, and only for short
periods of time.
More information about the general query log can be found at https://mariadb.
com/kb/en/general-query-log/.
The slow query log
The MariaDB slow query log, when enabled, contains a record of queries that take
longer than a configured amount of time to run. This log is very useful when tuning
and optimizing MariaDB as it stores lots of useful information such as the time it
took to execute a long query, the user who executed the query, the hostname the user
came from, and other details.
This log is disabled by default. To enable it we add the following to the [mysqld]
section of our my.cnf or my.ini config file:
slow_query_log = 1
There are four other variables that we use to control the behavior of the slow query
log. We use the slow_query_log_file variable to set the location of the log file. We
use the long_query_time variable to set the amount of time the query has to run
before MariaDB considers it to be slow. Times can be expressed in whole seconds
down to microsecond precision (0.000001).
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MariaDB Maintenance
The log_slow_rate_limit variable is used to control how often long queries
are actually logged. For example, a setting of 20 would log every twentieth query,
or 5 percent of the slow queries. This is useful if our slow query log is growing too
fast. If this variable is not present, the default is for the slow query log to log every
slow query.
Lastly, the log_slow_verbosity variable controls what information is logged.
Possible values include:
• microtime: Makes the log to log the queries in microseconds
• query_plan: Logs query execution plan information
• innodb: Adds additional statistical information about queries that touch
XtraDB and InnoDB tables
• standard: Turns on both the microtime and innodb variables
• full: Turns on all options
• profiling: Allows the logged queries to be profiled
We can specify multiple options if we separate them with commas. Here is an
example which turns on the slow query log and sets some common options:
slow_query_log = 1
slow_query_log_file = /var/log/mysql/mariadb-slow.log
long_query_time = 0.05
log_slow_rate_limit = 30
log_slow_verbosity = query_plan,standard
More information about the slow query log can be found at https://mariadb.com/
kb/en/slow-query-log/.
Optimizing and tuning MariaDB
The subject of tuning and optimizing MariaDB, and the applications that connect
to it, for maximum performance is worthy of a book in itself. We won't go into the
details of specific strategies here because it's generally not necessary when we're just
getting started with MariaDB. It is useful to know a little about the subject though,
which is explained in the following section.
The basic process of tuning and optimizing MariaDB starts with identifying the
choke points, that is, the places that are causing unnecessary slowdowns. Using the
slow query log to identify these choke points is a good place to start.
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Chapter 6
Once a problem query (or set of queries) has been identified, the next step is to
implement a fix of some sort. This could be as simple as rewriting the query to be
more efficient. Or it could be sped up by adding an index to the table.
We can also gather and examine user and table statistics to identify patterns of usage
that we can potentially optimize. Or we can examine our table definitions to see if
there are any tweaks that can be made there to make things faster or more efficient.
The list of ways to squeeze more performance out of MariaDB goes on and on.
If the query and our database are as optimized as we can make them, there are still
things that we can do. Hardware, for example, can be a limitation. A busy database
that needs to respond quickly needs to be on fast hardware. Fast disks, lots of
memory, and a fast processor are all important.
More information on optimizing and tuning MariaDB can be found at
https://mariadb.com/kb/en/optimization-and-tuning/.
Backing up MariaDB
MariaDB ships with a couple of utilities that can be used to back up our databases.
Data in MariaDB is written to special files on disk, so it may be tempting to think
that we can just backup the MariaDB data directory and be done. The problem with
this is that the data files are always open and in use while MariaDB is running and
problems can arise if we try to back up the files directly.
Basic backups with mysqldump
By default, the mysqldump client backup utility generates SQL backups. These
backups contain all the necessary SQL commands to recreate tables and restore the
data in those tables.
There are many options, but the basic syntax is as follows:
mysqldump [-u username] [-p] database_name [table_name]
If table_name is not given, mysqldump will backup all the tables in the named
database. For example, the following command will backup the entire test database:
mysqldump -u root -p test > test.sql
The output of mysqldump goes to standard out. When running the command from
a terminal, it will be echoed directly to the screen. So in the preceding example
command, we use the > redirect character to direct the output into a file named
test.sql.
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MariaDB Maintenance
To restore the preceding backup, we can use the mysql command-line client as
follows:
mysql -u root -p test < test.sql
As with the mysqldump example, we use a redirect character, but this time it is
redirecting in the opposite direction, from the test.sql file to the mysql client.
The mysql client reads the file and executes all of the SQL commands, restoring the
backed up tables and their data.
We can also use mysqldump to create tab-delimited files. This is done using the --tab
option. When using this option, mysqldump will create two files. A tablename.sql
file with the SQL commands to recreate the table, and a tablename.txt file with the
actual data in tab-delimited format. Here is an example using mysqldump and --tab
to backup up the employees table in our test database:
mysqldump --tab /tmp/ -u root -p test employees
The --tab option needs a directory after it where it can write the files. The SQL file is
owned by whichever user we used to run the mysqldump command. The TXT file, on
the other hand is owned by the mysql user, so whatever directory we specify needs
to have permissions so that both users can write to it. The /tmp/ directory is used in
the example since, by default on Linux, this directory can be written to by anyone.
So why would a tab-delimited file of our data be useful? Well, for starters, the
mysqlimport program reads tab-delimited files. Popular spreadsheets also read
and write to tab-delimited files. So, for example, if we've been keeping our data in
a spreadsheet, and have decided to move it to a MariaDB database, we can export
our spreadsheet data as a tab-delimited file, create the tables in MariaDB, and then
use mysqlimport to import our data. At a later point, we could use mysqldump to
dump the data or a subset of the data to a file and then open it with our spreadsheet
program, and create some nice pie charts or other graphs.
There are scores of other options that we can use to tweak and customize what and
how mysqldump backs up our data. It's well worth it to take the time necessary to
learn all of its many options.
Full documentation of the mysqldump utility is found at
https://mariadb.com/kb/en/mysqldump/.
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Chapter 6
Restoring and importing data with mysqlimport
We talked briefly about mysqlimport in the previous section. In short, this command
is used to import data into MariaDB. This data could be a backup that we made
previously or completely new data. There are several options, but the basic syntax is
as follows:
mysqlimport [--local] [-u username] [-p] database_name filename
The filename attribute must be the name of the table we want to import into. The
--local option tells mysqlimport to read from the local filesystem instead of from
the data directory of the server.
Here is an example importing the employees.txt file that we generated earlier:
sudo mysqlimport --local -u root -p test /tmp/employees.txt
Any records that cannot be imported will be skipped and not imported, and
mysqlimport will report this and generate a warning. An example would be if our
file has a column in it that contains values that must be unique in our database and if
some of them match the existing records in the database.
Full documentation of the mysqlimport utility is found at https://mariadb.com/
kb/en/mysqlimport.
Making backups of MyISAM tables quickly
with mysqlhotcopy
The mysqlhotcopy backup program is actually a Perl script. It can make backups
quickly, but only if our tables use the MyISAM or ARCHIVE storage engines. The
default storage engine for MariaDB is InnoDB, so this script is less useful than it
used to be back when MyISAM was the default storage engine. If we do have the
MyISAM tables, however, it remains a useful tool.
The basic syntax of the mysqlhotcopy command is as follows:
mysqlhotcopy db_name [/path/to/new_directory]
If a path to a new directory is not given, mysqlhotcopy will make the backup in the
MariaDB data directory.
Other limitations are that the command must be run by a user that can read the
data files in the data directory, and when connecting to MariaDB, if we use a
password, we must specify it on the command line or specify it in a my.cnf file as
mysqlhotcopy does not support prompting us for the password.
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MariaDB Maintenance
Full documentation of the mysqlhotcopy program is found at https://mariadb.
com/kb/en/mysqlhotcopy/.
Making cold backups
Another option for backing up MariaDB is to just copy the entire data directory. This
is called a cold backup. As mentioned at the beginning of this section, problems can
arise if we try to do this while MariaDB is running, but if we stop MariaDB briefly,
and are using a filesystem that supports snapshots (called shadow volume copies on
Windows) we can stop MariaDB briefly, make a snapshot, and then start MariaDB.
Total downtime for an operation such as this, depending on various factors, might be
only a few seconds. The snapshotted directory may then be backed up like any other
filesystem directory backup.
This is obviously not an ideal way to make backups in all situations, especially when
stopping the database server, even for a few seconds, is not an option. But it can
work very well in some cases.
Checking and repairing tables
After a hardware failure, after a power outage, or even after an upgrade, it is a good
idea to check the tables in our MariaDB databases to make sure they are ok. MariaDB
includes several utilities to do this.
Checking and optimizing tables with
mysqlcheck
The mysqlcheck program can check, analyze, optimize, and repair MariaDB
database tables. Basic syntax for the command is as follows:
mysqlcheck [options] [-u username] [-p] database_name [table_name]
Here is an example of running the command to check our test database, and its output:
daniel@gandalf:~$ mysqlcheck -u root -p test
Enter password:
test.employees
OK
We can specify multiple databases using the --databases option as follows:
mysqlcheck -u root -p --databases db_name1 db_name2 db_name3
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Chapter 6
We can also tell the program to check all of our databases with the --all-databases
option, as follows:
mysqlcheck -u root -p --all-databases
By default, mysqlcheck will only check tables when it is run. To get it to optimize,
analyze, or repair tables, we use one of the following options:
• --optimize
• --analyze
• --repair
Not all of the options work on all tables. For example, InnoDB tables cannot be
repaired with mysqlcheck. The program displays an error message if it cannot
perform a requested action.
Full documentation of the mysqlcheck utility is found at https://mariadb.com/
kb/en/mysqlcheck/.
Repairing tables
Thankfully, MariaDB is a very mature and stable program. Problems are few and
very far between. However, power does sometimes go out and hardware sometimes
fails catastrophically or gradually, so there may come a time when a table in our
database has problems and needs to be repaired.
MyISAM and Aria tables can often be repaired with the mysqlcheck program, so if
mysqlcheck reports that a table needs repairing then we can usually simply re-run
the program with the --repair option. Unfortunately, mysqlcheck cannot repair
InnoDB tables.
Thankfully, InnoDB and XtraDB are crash safe, which means they are protected
to a certain extent when failures do occur. This protection means that the chances
of a hardware failure causing corruption are very low. InnoDB and XtraDB also
have a built-in crash-recovery mechanism. The way to use it is to add the innodb_
force_recovery option to the [mysqld] section of our my.cnf or my.ini file with
it set to a number between 1 and 6. Setting this variable to 0 or removing it entirely
disables it. While this option is set, MariaDB will not allow any InnoDB tables to be
changed. The higher the number, the more aggressively MariaDB will try to repair
the tables. Full documentation of this feature is at https://mariadb.com/kb/en/
xtradbinnodb-recovery-modes/.
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MariaDB Maintenance
If innodb_force_recovery does not work, we may need to dump and reload our
affected tables. This procedure can take a long time on a large server, so it should
only be used as a last resort. The basic procedure to dump and reload a database is as
we went over in the mysqldump section previously, but here it is again:
mysqldump [options] database_name > dump.sql
mysql database_name < dump.sql
So to dump and reload our test database we might do the following:
mysqldump -u root -p test > dump.sql
mysql -u root -p test < dump.sql
This reload process can be more likely to succeed if it is used in conjunction with
the innodb_force_recovery variable. For example, a setting of 1 tells InnoDB and
XtraDB to skip corrupt indexes and records instead of attempting to read them.
Refer to the XtraDB/InnoDB Recovery Modes page in the MariaDB Knowledge Base
found previously in this section for more information.
If the preceding reload process doesn't fix the error, we might want to call in
some experts. There are various recovery strategies out there, but they are
beyond the scope of this book. We could also try reloading from a backup, we may
lose some data depending on how old the backup is, but losing some data is better
than losing everything.
Summary
In this chapter, we learned about the various MariaDB log files and what they are
used for. We also went over common backup methods and programs. We briefly
discussed optimization. Lastly, we wrapped things up with a discussion of various
things that we can do if something goes wrong.
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MariaDB Next Steps
This book provides an introduction to MariaDB, with enough information to get
us started. MariaDB is a large system with many parts, options, and capabilities.
So where do we go from here? If we have a question, where do we go for help?
Here is a list of various online resources available to help us on our way to becoming
a MariaDB expert.
Let's begin with the official MariaDB website. MariaDB downloads, the
MariaDB Foundation blog, and other official MariaDB information is found at
http://mariadb.org.
Next is the MariaDB Knowledge Base available at https://mariadb.com/. This is
the official location of MariaDB documentation. New information is being added
here on a daily basis. Whenever something is added to or changed in MariaDB it
is documented here. Release notes and change logs for MariaDB releases are also
posted here.
There is also an Ask a Question feature that can be used if you have a question about
something in MariaDB. Just navigate to the section or item you are interested in,
click on the button and ask away. You can also provide your own tips and tricks by
leaving comments on the page. Registration is required (to cut down on spam) but it
is free and all the content is released under either a Creative Commons, GFDL, or GPL
license. The direct link to MariaDB Knowledge Base is https://mariadb.com/kb/.
If we want to talk to someone right now, there are a few options. First is IRC,
where we can engage in real-time chat conversations with other users and with the
developers of MariaDB. The official MariaDB channel is #maria on the Freenode IRC
network. See the Knowledge Base entry on IRC (https://mariadb.com/kb/en/irc)
for more information.
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MariaDB Next Steps
To engage in a direct conversation, there are three MariaDB e-mail lists. The
developers list is for technical discussions about MariaDB development. The discuss
list is for general discussions about using MariaDB. The docs list is for discussion
and planning related to MariaDB documentation. All three lists are hosted on
launchpad.net. The most useful list for end users is the discuss list. Following are
the links to these lists:
• MariaDB developers list – https://launchpad.net/~maria-developers
• MariaDB discuss list – https://launchpad.net/~maria-discuss
• MariaDB docs list – https://launchpad.net/~maria-docs
Lastly, MariaDB is active on the major social media platforms. Here are the locations
of the official MariaDB accounts on Twitter, Google+, and Facebook:
• Twitter – http://twitter.com/mariadb
• Google+ – http://google.com/+mariadb
• Facebook – http://fb.com/MariaDB.dbms
I hope you enjoy working with MariaDB!
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Index
Symbols
--all-databases option 77
<alter_definition> attribute 60
<alter_definition> command 60
--databases option 76
--local option 75
-p option 52
--tab option 74
-u option 52
<what> section 65
cold backup
creating 76
column
adding 60
dropping 61
modifying 60
comments 25, 26
CREATE DATABASE command 54, 55
Create, Read, Update, and Delete (CRUD)
68
CREATE TABLE command 56, 59, 62
A
D
Advanced Package Tool (APT) 22
Advanced Packaging Tool. See APT
AFTER option 60
Alpha 8
ALTER TABLE command 56, 60
APT 7
Aria table 77
data
deleting 64
importing, mysqlimport used 75
inserting 62
reading 64-67
restoring, mysqlimport used 75
updating 63, 64
database
creating 54
dropping 54, 55
listing, on server 53
using 52, 53
database and table privileges
ALTER 42
ALTER ROUTINE 42
CREATE 42
CREATE ROUTINE 42
CREATE TEMPORARY TABLES 42
CREATE VIEW 43
DELETE 43
DROP 43
EVENT 43
B
backups
creating, mysqldump used 73, 74
Beta 8
binary log, MariaDB
about 69
URL 70
working 69, 70
Building 31
C
CentOS
MariaDB, installing on 15, 16
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EXECUTE 43
INDEX 43
INSERT 43
LOCK TABLES 43
SELECT 43
SHOW VIEW 43
TRIGGER 43
UPDATE 43
datatype 57
Debian
MariaDB, installing on 14
DELETE command 64
delimiter 53
DESCRIBE command 59
development series 8
DROP command 55
DROP DATABASE command 55
DROP TABLE command 61
general query log, MariaDB
about 71
URL 71
global administrative privileges
about 42
CREATE USER 42
FILE 42
PROCESS 42
RELOAD 42
REPLICATION CLIENT 42
REPLICATION SLAVE 42
SHOW DATABASES 42
SHUTDOWN 42
SUPER 42
Gnu Privacy Guard (GPG) 18
I
E
Enable networking option 11
error log, MariaDB
about 70
URL 70
event 69
F
Fedora
MariaDB, installing on 15, 16
filename attribute 75
filesystem layout, MariaDB
about 21
comments 25- 27
configuration changes, activating 28
for Linux 22, 23
for Windows 21, 22
MariaDB configuration file 25
modular configuration 24
options 28
FIRST option 60
foreign keys 56
G
general_log_file variable 71
general_log variable 71
IF NOT EXISTS command 57
InnoDB 75
innodb_force_recovery variable 78
innodb variable 72
INSERT command 63
Install as service box 11
installing
MariaDB, on CentOS 15, 17
MariaDB, on Debian 14, 15
MariaDB, on Fedora 15-17
MariaDB, on Linux Mint 14, 15
MariaDB, on Mac OS X 13
MariaDB, on other Linux distribution 17
MariaDB, on Red Hat 15-17
MariaDB, on Ubuntu 14, 15
MariaDB, on Windows 10-13
Internal Network 31
internal network security 38
Internet 31
internet security 39
L
Linux
filesystem layout 22, 23
Linux Mint
MariaDB, installing on 14
log_bin variable 69
log_error variable 70
log_slow_rate_limit variable 72
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log_slow_verbosity variable 72
long_query_time variable 71
M
Mac OS X
MariaDB, installing on 13
maintenance series 9
MariaDB
about 21, 51, 79
backing up 73-76
comparison operators, URL 66
connecting to 34-36
database, creating 54
database, dropping 54, 55
database, using 52, 53
data, deleting 64
data, inserting 62
data, reading 64-67
data, updating 63, 64
end users list 80
filesystem layout 21
installing, on CentOS 15-17
installing, on Debian 14, 15
installing, on Fedora 15-17
installing, on Linux Mint 14, 15
installing, on Mac OS X 13
installing, on other Linux Distributions 17
installing, on Red Hat 15-17
installing, on Ubuntu 14, 15
installing, on Windows 10-13
internal network security 38
internet security 39
Knowledge Base 79
log files 69-72
on Facebook 80
on Google+ 80
on Twitter 80
optimizing 72, 73
optimizing, URL 73
post installation 18, 19
securing 32, 34
security 31
security, building 37
server security 36
supported data types, URL 57
tuning 72, 73
tuning, URL 73
user privileges 41
Window installations, MSI packages 10
Window installations, ZIP files 10
working 52
MariaDB back up
basic backups, mysqldump used 73, 74
cold backups, creating 76
data importing, mysqlimport used 75
data restoring, mysqlimport used 75
MyISAM tables backup, creating 75
MariaDB configuration file 25
MariaDB installation
issues 19
MariaDB log files
about 69
binary log 69, 70
error log 70
general query log 71
slow query log 71, 72
types 69
MariaDB Package Security 18
MariaDB series
choosing 8
development series 8
maintenance series 9
stable series 9
microtime variable 72
miscellaneous privileges
about 43
ALL PRIVILEGES 43
GRANT OPTION 43
limits, MAX_CONNECTIONS_PER_HOUR
44
limits, MAX_QUERIES_PER_HOUR 44
limits, MAX_UPDATES_PER_HOUR 44
limits, MAX_USER_CONNECTIONS 44
USAGE 43
modular configuration 23, 24
my.cnf files function 23
MyISAM table 77
MyISAM tables backup
creating, mysqlhotcopy used 75
mysqlbinlog program 70
mysqlcheck program
URL 77
used, for checking tables 76, 77
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used, for optimizing tables 76, 77
used, for repairing tables 77, 78
mysql command-line client
running 51, 52
mysqldump
URL 74
used, for backup creating 73, 74
mysqlhotcopy
URL 76
used, for MyISAM tables backup creating
75
mysqlimport
used, for data importing 75
used, for data restoring 75
normalization 56
server security, MariaDB 36
shadow volume copies. See snapshots
SHOW CREATE TABLE command 58
SHOW DATABASES command 53
SHOW GRANTS command 48
slow_query_log_file variable 71
slow query log, MariaDB
about 71
log_slow_rate_limit variable 72
log_slow_verbosity variable 72
long_query_time variable 71
slow_query_log_file variable 71
switching on 72
URL 72
snapshots 76
SQL 53
stable series 9
Structured Query Language. See SQL
O
T
N
Optimize for transactions checkbox 12
ORDER BY clause 66
P
passwords
changing 48
performance_schema database 54
permissions
granting 45
grants, showing 47
physical security 32
Pretty Good Privacy (PGP) 18
primary key 58
R
Red Hat
MariaDB, installing on 15, 16
relational database 56
S
SELECT command 64, 67
series 8
server
about 32
databases, listing on 53
table alteration
column, adding 60
column, dropping 61
column, modifying 60
table creation
create table command, showing 58, 59
table structure, exploring 59
tables
altering 60, 61
checking, mysqlcheck used 76, 77
creating 56-59
dropping 61
optimizing, mysqlcheck used 76, 77
repairing, mysqlcheck used 77, 78
test database 58
U
Ubuntu
MariaDB, installing on 14
UPDATE command 63, 64
USE command 52
user privileges
adding 47
database and table privileges 42
global administrative privileges 42
miscellaneous privileges 43
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removing 47
users
creating 44
removing 48
W
WHERE clause 67
wildcard character 67
Windows
filesystem layout 21, 22
MariaDB, installing on 10-12
X
XtraDB/InnoDB Recovery Modes page 78
Y
Yellow Dog Updater, Modified. See YUM
Yellow Dog Updater, Modified (YUM) 22
YUM 7
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CouchDB and PHP Web
Development Beginner's Guide
ISBN: 978-1-84951-358-6
Paperback: 304 pages
Get your PHP application from conception to
deployment by leveraging CouchDB's robust features
1.
Build and deploy a flexible Social Networking
application using PHP and leveraging key
features of CouchDB to do the heavy lifting
2.
Explore the features and functionality
of CouchDB, by taking a deep look into
Documents, Views, Replication, and much
more.
3.
Conceptualize a lightweight PHP framework
from scratch and write code that can easily port
to other frameworks
Please check www.PacktPub.com for information on our titles
www.it-ebooks.info
Mastering phpMyAdmin 3.4 for
Effective MySQL Management
ISBN: 978-1-84951-778-2
Paperback: 394 pages
A complete guide to getting started with
phpMyAdmin 3.4 and mastering its features
1.
A step-by-step tutorial for manipulating data
with the latest version of phpmyadmin
2.
Administer your MySQL databases with
phpMyAdmin
3.
Manage users and privileges with MySQL
Server Administration tools
4.
Learn to do things with your MySQL database
and phpMyAdmin that you didn't know were
possible!
Ruby and MongoDB Web
Development Beginner's Guide
ISBN: 978-1-84951-502-3
Paperback: 332 pages
Create dynamic web applications by combinig the
power of Ruby and MongoDB
1.
Step-by-step instructions and practical
examples to creating web applications with
Ruby and MongoDB
2.
Learn to design the object model in a NoSQL
way
3.
Create objects in Ruby and map them to
MongoDB
Please check www.PacktPub.com for information on our titles
www.it-ebooks.info
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