Difference between revisions of "MySQL"

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MySQL is a widely spread, multi-threaded, multi-user SQL database. For more information about features, see the [http://www.mysql.com/ official homepage].
 
MySQL is a widely spread, multi-threaded, multi-user SQL database. For more information about features, see the [http://www.mysql.com/ official homepage].
  
{{Note|MariaDB is now officially our default implementation of MySQL.It is recommended for all users to upgrade to [[MariaDB]]. MySQL will be dropped from the repositories to the AUR before 2013/4/26. See [https://www.archlinux.org/news/mariadb-replaces-mysql-in-repositories/ the announcement].}}
+
{{Note|MariaDB is now officially Arch Linux default implementation of MySQL. It is recommended for all users to [[#Upgrade from Oracle MySQL to MariaDB|upgrade]] to MariaDB. Oracle MySQL was dropped to the AUR. See [https://www.archlinux.org/news/mariadb-replaces-mysql-in-repositories/ the announcement].}}
 +
 
 +
== Installation ==
 +
 
 +
The MySQL implementation chosen by Archlinux is called MariaDB.
 +
[[pacman|Install]] {{Pkg|mariadb}}, {{Pkg|libmariadbclient}}, {{Pkg|mariadb-clients}} packages from the [[official repositories]].
 +
Alternate implementations are {{Pkg|percona-server}} and Oracle {{AUR|mysql}}.
 +
 
 +
{{Tip|If the database (in /var/lib/mysql) resides in a [[btrfs]] filesystem you should consider disabling [[Btrfs#Copy-On-Write_.28CoW.29|Copy-on-Write]] for the directory before creating any database:
 +
{{ic|# chattr +C /var/lib/mysql}}
 +
}}
 +
 
 +
Start the {{ic|mysqld}} [[daemon]], run the setup script and restart the daemon afterwards:
 +
# systemctl start mysqld
 +
# mysql_secure_installation
 +
# systemctl restart mysqld
 +
 
 +
Frontends available are {{AUR|mysql-gui-tools}} and {{AUR|mysql-workbench}}.
 +
 
 +
=== Enable at startup ===
 +
 
 +
To enable mysql daemon to start at boot, add the service to systemd
 +
  # systemctl enable mysqld.service
 +
 
 +
=== Upgrade from Oracle MySQL to MariaDB ===
  
== Upgrade to MariaDB ==
 
 
Users who want to switch will need to install mariadb, libmariadbclient or mariadb-clients and execute mysql_upgrade in order to migrate their systems.
 
Users who want to switch will need to install mariadb, libmariadbclient or mariadb-clients and execute mysql_upgrade in order to migrate their systems.
 
  # systemctl stop mysqld
 
  # systemctl stop mysqld
Line 19: Line 42:
 
  # mysql_upgrade -p
 
  # mysql_upgrade -p
  
== Installation ==
+
Notice that it could be needed to remove the following files from {{ic|/var/lib/mysql}} : {{ic|ib_logfile0}}, {{ic|ib_logfile1}} and {{ic|aria_log_control}} before starting the daemon.
[[pacman|Install]] the {{Pkg|mysql}} package from the [[Official Repositories|official repositories]].
+
  
After installing MySQL, start the ''mysqld'' [[Daemons|daemon]].
+
=== On update ===
  
Run the setup script and restart the daemon afterwards:
+
You might consider running this command after you have upgraded MySQL and started it:
  # mysql_secure_installation
+
  # mysql_upgrade -u root -p
# systemctl restart mysqld
+
  
 
== Configuration ==
 
== Configuration ==
 +
 
Once you have started the MySQL server, you probably want to add a root account in order to maintain your MySQL users and databases. This can be done manually or automatically, as mentioned by the output of the above script. Either run the commands to set a password for the root account, or run the secure installation script.
 
Once you have started the MySQL server, you probably want to add a root account in order to maintain your MySQL users and databases. This can be done manually or automatically, as mentioned by the output of the above script. Either run the commands to set a password for the root account, or run the secure installation script.
  
Line 35: Line 57:
  
 
=== Disable remote access ===
 
=== Disable remote access ===
The MySQL server is accessible from the network by default. If mysql is only needed for the localhost, you can improve security by not listening on TCP port 3306. To refuse remote connections, uncomment the following line in {{ic|/etc/mysql/my.cnf}}:
+
 
 +
The MySQL server is accessible from the network by default. If MySQL is only needed for the localhost, you can improve security by not listening on TCP port 3306. To refuse remote connections, uncomment the following line in {{ic|/etc/mysql/my.cnf}}:
 
  skip-networking
 
  skip-networking
  
Line 41: Line 64:
  
 
=== Enable auto-completion ===
 
=== Enable auto-completion ===
The MySQL client completion feature is disabled by default. To enable it system-wide edit {{ic|/etc/mysql/my.cnf}}, and replace {{ic|no-auto-rehash}} by {{ic|auto-rehash}}. Completion will be enabled next time you run the MySQL client. Please note that enabling this feature can make the client initialization longer.
 
  
== Upgrading ==
+
{{Note|Enabling this feature can make the client initialization longer.}}
You might consider running this command after you have upgraded MySQL and started it:
+
The MySQL client completion feature is disabled by default. To enable it system-wide edit {{ic|/etc/mysql/my.cnf}}, and replace {{ic|no-auto-rehash}} by {{ic|auto-rehash}}. Completion will be enabled next time you run the MySQL client.
  # mysql_upgrade -u root -p
+
 
 +
=== Using UTF-8 ===
 +
 
 +
In the {{ic|/etc/mysql/my.cnf}} file section under the "mysqld" group, add:
 +
 
 +
{{bc|<nowiki>[mysqld]
 +
init_connect                = 'SET collation_connection = utf8_general_ci,NAMES utf8'
 +
collation_server            = utf8_general_ci
 +
character_set_client        = utf8
 +
character_set_server        = utf8</nowiki>}}
 +
 
 +
=== Using a TMPFS for tmpdir ===
 +
 
 +
The directory used by MySQL for storing temporary files is named "tmpdir".  For example, it is used to perform disk based large sorts, as well as for internal and explicit temporary tables.
 +
 
 +
Create the directory with appropriate permissions:
 +
  $ mkdir -pv /var/lib/mysqltmp
 +
$ chown mysql:mysql /var/lib/mysqltmp
 +
 
 +
Find the id and gid of the "mysql" user and group:
 +
$ id mysql
 +
uid=27(mysql) gid=27(mysql) groups=27(mysql)
 +
 
 +
Add to your {{ic|/etc/fstab}} file.
 +
  tmpfs  /var/lib/mysqltmp  tmpfs  rw,gid=27,uid=27,size=100m,mode=0750,noatime  0 0
 +
 
 +
Add to your {{ic|/etc/mysql/my.cnf}} file under the "mysqld" group:
 +
  tmpdir      = /var/lib/mysqltmp
 +
 
 +
Then reboot or ( shutdown mysql, mount the tmpdir, start mysql ).
  
 
== Backup ==
 
== Backup ==
 +
 
The database can be dumped to a file for easy backup.  The following shell script will do this for you, creating a {{ic|db_backup.gz}} file in the same directory as the script, containing your database dump:
 
The database can be dumped to a file for easy backup.  The following shell script will do this for you, creating a {{ic|db_backup.gz}} file in the same directory as the script, containing your database dump:
  
Line 53: Line 105:
 
#!/bin/bash
 
#!/bin/bash
  
THISDIR=`dirname $(readlink -f "$0")`
+
THISDIR=$(dirname $(readlink -f "$0"))
  
 
mysqldump --single-transaction --flush-logs --master-data=2 --all-databases \
 
mysqldump --single-transaction --flush-logs --master-data=2 --all-databases \
  <nowiki>|</nowiki> gzip > $THISDIR/db_backup.gz
+
<nowiki>| gzip > $THISDIR/db_backup.gz
echo 'purge master logs before date_sub(now(), interval 7 day);' <nowiki>|</nowiki> mysql
+
echo 'purge master logs before date_sub(now(), interval 7 day);' |</nowiki> mysql
 
}}
 
}}
  
See also the official [http://dev.mysql.com/doc/refman/5.6/en/mysqldump.html mysqldump page in the MySQL manual].
+
See also the official {{ic|mysqldump}} [http://dev.mysql.com/doc/refman/5.6/en/mysqldump.html page] in the MySQL manual.
  
 
== Troubleshooting ==
 
== Troubleshooting ==
 +
 
=== MySQL daemon cannot start ===
 
=== MySQL daemon cannot start ===
If you see something like this:
+
 
  :: Starting MySQL [FAIL]
+
If MySQL fails to start and there is no entry in the log files, you might want to check the permissions of files in the directories {{ic|/var/lib/mysql}} and {{ic|/var/lib/mysql/mysql}}. If the owner of files in these directories is not {{ic|mysql:mysql}}, you should do the following:
and there is no entry in the log files, you might want to check the permissions of files in the directories {{ic|/var/lib/mysql}} and {{ic|/var/lib/mysql/mysql}}. If the owner of files in these directories is not {{ic|mysql:mysql}}, you should do the following:
+
# chown mysql:mysql /var/lib/mysql -R
  # chown mysql:mysql /var/lib/mysql -R
+
 
If you run into permission problems despite having followed the above, ensure that your {{ic|my.cnf}} is copied to {{ic|/etc/}}:
 
If you run into permission problems despite having followed the above, ensure that your {{ic|my.cnf}} is copied to {{ic|/etc/}}:
  # cp /etc/mysql/my.cnf /etc/my.cnf
+
# cp /etc/mysql/my.cnf /etc/my.cnf
 
Now try and start the daemon.
 
Now try and start the daemon.
  
 
If you get these messages in your {{ic|/var/lib/mysql/hostname.err}}
 
If you get these messages in your {{ic|/var/lib/mysql/hostname.err}}
  [ERROR] Can't start server : Bind on unix socket: Permission denied
+
[ERROR] Can't start server : Bind on unix socket: Permission denied
  [ERROR] Do you already have another mysqld server running on socket: /var/run/mysqld/mysqld.sock ?
+
[ERROR] Do you already have another mysqld server running on socket: /var/run/mysqld/mysqld.sock ?
  [ERROR] Aborting
+
[ERROR] Aborting
 
The permissions of {{ic|/var/run/mysqld}} could be the culprit.
 
The permissions of {{ic|/var/run/mysqld}} could be the culprit.
  # chown mysql:mysql /var/run/mysqld -R
+
# chown mysql:mysql /var/run/mysqld -R
  
 
If you run mysqld and the following error appears:
 
If you run mysqld and the following error appears:
  Fatal error: Can’t open and lock privilege tables: Table ‘mysql.host’ doesn’t exist
+
Fatal error: Can’t open and lock privilege tables: Table ‘mysql.host’ doesn’t exist
Run the following command from the /usr directory to install the default tables:
+
Run the following command from the {{ic|/usr}} directory to install the default tables:
  # cd /usr
+
# cd /usr
  # mysql_install_db --user=mysql --ldata=/var/lib/mysql/
+
# mysql_install_db --user=mysql --ldata=/var/lib/mysql/
  
 
=== Unable to run mysql_upgrade because MySQL cannot start ===
 
=== Unable to run mysql_upgrade because MySQL cannot start ===
 +
 
Try run MySQL in safemode:
 
Try run MySQL in safemode:
 
  # mysqld_safe --datadir=/var/lib/mysql/
 
  # mysqld_safe --datadir=/var/lib/mysql/
Line 92: Line 145:
  
 
=== Reset the root password ===
 
=== Reset the root password ===
Stop the ''mysqld'' [[Daemons|daemon]].
+
 
 +
Stop the ''mysqld'' [[daemon]]. Issue the following command:
 
  # mysqld_safe --skip-grant-tables &
 
  # mysqld_safe --skip-grant-tables &
Connect to the mysql server
+
Connect to the mysql server. Issue the following command:
 
  # mysql -u root mysql
 
  # mysql -u root mysql
 
Change root password:
 
Change root password:
  mysql> UPDATE mysql.user SET Password=PASSWORD('MyNewPass') WHERE User='root';
+
mysql> UPDATE mysql.user SET Password=PASSWORD('MyNewPass') WHERE User='root';
  mysql> FLUSH PRIVILEGES;
+
mysql> FLUSH PRIVILEGES;
  mysql> exit
+
mysql> exit
 
Start the ''mysqld'' daemon.
 
Start the ''mysqld'' daemon.
 +
 +
=== Check and repair all tables ===
 +
 +
Check and auto repair all tables in all databases, [http://dev.mysql.com/doc/refman/5.7/en/mysqlcheck.html see more]
 +
# mysqlcheck -A --auto-repair -u root -p
 +
 +
=== Optimize all tables ===
 +
 +
Forcefully Optimize all tables, automatically fixing table errors that may come up.
 +
# mysqlcheck -A --auto-repair -f -o -u root -p
  
 
== See also ==
 
== See also ==
 +
 
* [[LAMP]] - Arch wiki article covering the setup of a LAMP server (Linux Apache MySQL PHP)
 
* [[LAMP]] - Arch wiki article covering the setup of a LAMP server (Linux Apache MySQL PHP)
* http://www.mysql.com/
+
* [[PhpMyAdmin]] - Arch wiki article covering the web-based tool to help manage MySQL databases using an Apache/PHP frontend.
* Front-ends: {{AUR|mysql-gui-tools}} {{AUR|mysql-workbench}}
+
* [[PHP]] - Archi wiki article on PHP.
 +
 
 +
== External links ==
 +
 
 +
* [https://mariadb.org/ MariaDB Official Website]
 +
* [http://www.mysql.com/ Oracle MySQL Official Website]
 +
* [http://www.percona.com/software Percona Software for MySQL]
 +
* [http://www.askapache.com/mysql/performance-tuning-mysql.html MySQL Performance Tuning Scripts and Know-How]

Revision as of 11:30, 19 August 2013

MySQL is a widely spread, multi-threaded, multi-user SQL database. For more information about features, see the official homepage.

Note: MariaDB is now officially Arch Linux default implementation of MySQL. It is recommended for all users to upgrade to MariaDB. Oracle MySQL was dropped to the AUR. See the announcement.

Installation

The MySQL implementation chosen by Archlinux is called MariaDB. Install mariadb, libmariadbclient, mariadb-clients packages from the official repositories. Alternate implementations are percona-server and Oracle mysqlAUR.

Tip: If the database (in /var/lib/mysql) resides in a btrfs filesystem you should consider disabling Copy-on-Write for the directory before creating any database:

# chattr +C /var/lib/mysql

Start the mysqld daemon, run the setup script and restart the daemon afterwards:

# systemctl start mysqld
# mysql_secure_installation
# systemctl restart mysqld

Frontends available are mysql-gui-toolsAUR and mysql-workbenchAUR.

Enable at startup

To enable mysql daemon to start at boot, add the service to systemd

 # systemctl enable mysqld.service

Upgrade from Oracle MySQL to MariaDB

Users who want to switch will need to install mariadb, libmariadbclient or mariadb-clients and execute mysql_upgrade in order to migrate their systems.

# systemctl stop mysqld
# pacman -S mariadb libmariadbclient mariadb-clients
# systemctl start mysqld
# mysql_upgrade -p

Notice that it could be needed to remove the following files from /var/lib/mysql : ib_logfile0, ib_logfile1 and aria_log_control before starting the daemon.

On update

You might consider running this command after you have upgraded MySQL and started it:

# mysql_upgrade -u root -p

Configuration

Once you have started the MySQL server, you probably want to add a root account in order to maintain your MySQL users and databases. This can be done manually or automatically, as mentioned by the output of the above script. Either run the commands to set a password for the root account, or run the secure installation script.

You now should be able to do further configuration using your favorite interface. For example you can use MySQL's command line tool to log in as root into your MySQL server:

$ mysql -p -u root

Disable remote access

The MySQL server is accessible from the network by default. If MySQL is only needed for the localhost, you can improve security by not listening on TCP port 3306. To refuse remote connections, uncomment the following line in /etc/mysql/my.cnf:

skip-networking

You will still be able to log in from the localhost.

Enable auto-completion

Note: Enabling this feature can make the client initialization longer.

The MySQL client completion feature is disabled by default. To enable it system-wide edit /etc/mysql/my.cnf, and replace no-auto-rehash by auto-rehash. Completion will be enabled next time you run the MySQL client.

Using UTF-8

In the /etc/mysql/my.cnf file section under the "mysqld" group, add:

[mysqld]
init_connect                = 'SET collation_connection = utf8_general_ci,NAMES utf8'
collation_server            = utf8_general_ci
character_set_client        = utf8
character_set_server        = utf8

Using a TMPFS for tmpdir

The directory used by MySQL for storing temporary files is named "tmpdir". For example, it is used to perform disk based large sorts, as well as for internal and explicit temporary tables.

Create the directory with appropriate permissions:

$ mkdir -pv /var/lib/mysqltmp
$ chown mysql:mysql /var/lib/mysqltmp

Find the id and gid of the "mysql" user and group:

$ id mysql
uid=27(mysql) gid=27(mysql) groups=27(mysql)

Add to your /etc/fstab file.

 tmpfs   /var/lib/mysqltmp   tmpfs   rw,gid=27,uid=27,size=100m,mode=0750,noatime   0 0

Add to your /etc/mysql/my.cnf file under the "mysqld" group:

 tmpdir      = /var/lib/mysqltmp

Then reboot or ( shutdown mysql, mount the tmpdir, start mysql ).

Backup

The database can be dumped to a file for easy backup. The following shell script will do this for you, creating a db_backup.gz file in the same directory as the script, containing your database dump:

#!/bin/bash

THISDIR=$(dirname $(readlink -f "$0"))

mysqldump --single-transaction --flush-logs --master-data=2 --all-databases \
 | gzip > $THISDIR/db_backup.gz
echo 'purge master logs before date_sub(now(), interval 7 day);' | mysql

See also the official mysqldump page in the MySQL manual.

Troubleshooting

MySQL daemon cannot start

If MySQL fails to start and there is no entry in the log files, you might want to check the permissions of files in the directories /var/lib/mysql and /var/lib/mysql/mysql. If the owner of files in these directories is not mysql:mysql, you should do the following:

# chown mysql:mysql /var/lib/mysql -R

If you run into permission problems despite having followed the above, ensure that your my.cnf is copied to /etc/:

# cp /etc/mysql/my.cnf /etc/my.cnf

Now try and start the daemon.

If you get these messages in your /var/lib/mysql/hostname.err

[ERROR] Can't start server : Bind on unix socket: Permission denied
[ERROR] Do you already have another mysqld server running on socket: /var/run/mysqld/mysqld.sock ?
[ERROR] Aborting

The permissions of /var/run/mysqld could be the culprit.

# chown mysql:mysql /var/run/mysqld -R

If you run mysqld and the following error appears:

Fatal error: Can’t open and lock privilege tables: Table ‘mysql.host’ doesn’t exist

Run the following command from the /usr directory to install the default tables:

# cd /usr
# mysql_install_db --user=mysql --ldata=/var/lib/mysql/

Unable to run mysql_upgrade because MySQL cannot start

Try run MySQL in safemode:

# mysqld_safe --datadir=/var/lib/mysql/

And then run:

# mysql_upgrade -u root -p

Reset the root password

Stop the mysqld daemon. Issue the following command:

# mysqld_safe --skip-grant-tables &

Connect to the mysql server. Issue the following command:

# mysql -u root mysql

Change root password:

mysql> UPDATE mysql.user SET Password=PASSWORD('MyNewPass') WHERE User='root';
mysql> FLUSH PRIVILEGES;
mysql> exit

Start the mysqld daemon.

Check and repair all tables

Check and auto repair all tables in all databases, see more

# mysqlcheck -A --auto-repair -u root -p

Optimize all tables

Forcefully Optimize all tables, automatically fixing table errors that may come up.

# mysqlcheck -A --auto-repair -f -o -u root -p

See also

  • LAMP - Arch wiki article covering the setup of a LAMP server (Linux Apache MySQL PHP)
  • PhpMyAdmin - Arch wiki article covering the web-based tool to help manage MySQL databases using an Apache/PHP frontend.
  • PHP - Archi wiki article on PHP.

External links