Difference between revisions of "MySQL"
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[[zh-CN:MySQL]] | [[zh-CN:MySQL]] | ||
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 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 == | == Installation == | ||
− | |||
− | + | The MySQL implementation chosen by Arch Linux is called [https://mariadb.org/ MariaDB]. | |
+ | [[pacman|Install]] {{Pkg|mariadb}}, {{Pkg|libmariadbclient}}, {{Pkg|mariadb-clients}} packages from the [[official repositories]]. | ||
+ | Alternative implementations are: | ||
+ | * {{App|Oracle MySQL|"The world's most popular open source database". Oracle official implementation.|https://www.mysql.com/|{{AUR|mysql}}}} | ||
+ | * {{App|Percona Server|Alternative which offers breakthrough performance, scalability, features, and instrumentation.|http://www.percona.com/software/percona-server/|{{Pkg|percona-server}}}} | ||
+ | |||
+ | {{Tip|If the database (in {{ic|/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 ''mysqld'' [[daemon]], run the setup script: | ||
# mysql_secure_installation | # mysql_secure_installation | ||
+ | and restart the daemon afterwards. | ||
+ | |||
+ | Frontends available are {{AUR|mysql-gui-tools}} and {{AUR|mysql-workbench}}. | ||
+ | |||
+ | === Enable at startup === | ||
+ | |||
+ | To enable mysql daemon to start at boot, add the {{ic|mysqld}} service to systemd: | ||
+ | # systemctl enable mysqld.service | ||
+ | |||
+ | === Upgrade from Oracle MySQL to MariaDB === | ||
+ | |||
+ | {{Note| | ||
+ | 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 restarting the daemon in the following procedure.}} | ||
+ | |||
+ | Users who want to switch will need to stop their current {{ic|mysqld}} daemon, install ''mariadb'', ''libmariadbclient'' or ''mariadb-clients'', restart {{ic|mysqld}}and execute: | ||
+ | # mysql_upgrade -p | ||
+ | in order to migrate their systems. | ||
+ | |||
+ | === On update === | ||
− | + | You might consider running this command after you have upgraded MySQL and started it: | |
+ | # mysql_upgrade -u root -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. | ||
Line 23: | Line 56: | ||
$ mysql -p -u root | $ mysql -p -u root | ||
− | === | + | === Disable remote access === |
− | The MySQL server is | + | |
+ | 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 | ||
+ | |||
+ | You will still be able to log in from the localhost. | ||
=== Enable auto-completion === | === 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 {{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. | |
− | # | + | |
+ | === Using UTF-8 === | ||
+ | |||
+ | In the {{ic|/etc/mysql/my.cnf}} file section under the {{ic|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 {{ic|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 {{ic|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 {{ic|db_backup.gz}} file in the same directory as the script, containing your database dump: | ||
+ | |||
+ | {{bc|1= | ||
+ | #!/bin/bash | ||
+ | |||
+ | THISDIR=$(dirname $(readlink -f "$0")) | ||
+ | |||
+ | mysqldump --single-transaction --flush-logs --master-data=2 --all-databases \ | ||
+ | <nowiki>| gzip > $THISDIR/db_backup.gz | ||
+ | echo 'purge master logs before date_sub(now(), interval 7 day);' |</nowiki> mysql | ||
+ | }} | ||
+ | |||
+ | 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 | + | |
− | + | 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 |
− | |||
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 | |
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] Do you already have another mysqld server running on socket: /var/run/mysqld/mysqld.sock ? | |
− | + | [ERROR] Aborting | |
− | + | the permissions of {{ic|/var/run/mysqld}} could be the culprit. | |
− | + | # 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 | |
− | 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 | |
− | + | # 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 64: | Line 145: | ||
=== Reset the root password === | === Reset the root password === | ||
− | [[ | + | |
+ | 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> FLUSH PRIVILEGES; | |
− | + | mysql> exit | |
− | [ | + | 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 == | ||
− | |||
* [[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. | + | * [[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. | |
+ | * [http://www.askapache.com/mysql/performance-tuning-mysql.html MySQL Performance Tuning Scripts and Know-How] |
Revision as of 04:12, 5 September 2013
zh-CN:MySQL MySQL is a widely spread, multi-threaded, multi-user SQL database. For more information about features, see the official homepage.
Installation
The MySQL implementation chosen by Arch Linux is called MariaDB. Install mariadb, libmariadbclient, mariadb-clients packages from the official repositories. Alternative implementations are:
- Oracle MySQL — "The world's most popular open source database". Oracle official implementation.
- https://www.mysql.com/ || mysqlAUR
- Percona Server — Alternative which offers breakthrough performance, scalability, features, and instrumentation.
/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:
# mysql_secure_installation
and restart the daemon afterwards.
Frontends available are mysql-gui-toolsAUR and mysql-workbenchAUR.
Enable at startup
To enable mysql daemon to start at boot, add the mysqld
service to systemd:
# systemctl enable mysqld.service
Upgrade from Oracle MySQL to MariaDB
/var/lib/mysql
: ib_logfile0
, ib_logfile1
and aria_log_control
before restarting the daemon in the following procedure.Users who want to switch will need to stop their current mysqld
daemon, install mariadb, libmariadbclient or mariadb-clients, restart mysqld
and execute:
# mysql_upgrade -p
in order to migrate their systems.
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
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.
- MySQL Performance Tuning Scripts and Know-How