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 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].}}
 
+
== 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.
+
# systemctl stop mysqld
+
# pacman -S mariadb libmariadbclient mariadb-clients
+
# systemctl start mysqld
+
# mysql_upgrade -p
+
  
 
== Installation ==
 
== Installation ==
[[pacman|Install]] the {{Pkg|mysql}} package from the [[Official Repositories|official repositories]].
 
  
After installing MySQL, start the ''mysqld'' [[Daemons|daemon]].
+
The MySQL implementation choosen by Archlinux is called MariaDB.
 +
[[pacman|Install]] {{Pkg|mariadb}}, {{Pkg|libmariadbclient}}, {{Pkg|mariadb-clients}} packages from the [[official repositories]].
 +
Alternate implamantations are {{Pkg|percona-server}} and Oracle {{Pkg|mysql}}.
  
Run the setup script and restart the daemon afterwards:
+
Start the {{ic|mysqld}} [[daemon]], run the setup script and restart the daemon afterwards:
 +
# systemctl start mysqld
 
  # mysql_secure_installation
 
  # mysql_secure_installation
 
  # systemctl restart mysqld
 
  # systemctl restart mysqld
 +
 +
=== 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
  
 
== 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.
  
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=== 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
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=== 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.
 
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 ==
 
== Upgrading ==
 +
 
You might consider running this command after you have upgraded MySQL and started it:
 
You might consider running this command after you have upgraded MySQL and started it:
 
  # mysql_upgrade -u root -p
 
  # mysql_upgrade -u root -p
  
 
== 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:
  
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#!/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
 
}}
 
}}
  
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== 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/}}:
Line 86: Line 94:
  
 
=== 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/
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=== 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:
Line 103: Line 113:
  
 
== 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/
 
* http://www.mysql.com/
 
* Front-ends: {{AUR|mysql-gui-tools}} {{AUR|mysql-workbench}}
 
* Front-ends: {{AUR|mysql-gui-tools}} {{AUR|mysql-workbench}}

Revision as of 20:51, 23 May 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 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 the announcement.

Installation

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

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

# systemctl start mysqld
# mysql_secure_installation
# systemctl restart mysqld

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

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

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. Please note that enabling this feature can make the client initialization longer.

Upgrading

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

# mysql_upgrade -u root -p

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.

See also