Difference between revisions of "MySQL"
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=== Enable at startup === | === Enable at startup === | ||
To start the MySQL daemon at boot, enable {{ic|mysqld}} [[systemd]] service. | To start the MySQL daemon at boot, enable {{ic|mysqld}} [[systemd]] service. | ||
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=== Upgrade from Oracle MySQL to MariaDB === | === Upgrade from Oracle MySQL to MariaDB === |
Revision as of 13:30, 28 February 2014
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 from the official repositories. Alternative implementations are:
- Oracle MySQL — An implementation by Oracle Corporation.
- https://www.mysql.com/ || mysqlAUR
- Percona Server — An implementation by Percona LLC.
/var/lib/mysql
) resides in a btrfs file system 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.
Front-ends available are mysql-gui-toolsAUR and mysql-workbenchAUR.
Enable at startup
To start the MySQL daemon at boot, enable mysqld
systemd 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
OS error 22 when running on ZFS
If you are using ZFS and get the following error:
InnoDB: Operating system error number 22 in a file operation.
You need to disable aio_writes by adding a line to the mysqld-section in /etc/mysql/my.cnf
[mysqld] ... innodb_use_native_aio = 0
See also
- LAMP - ArchWiki article covering the setup of a LAMP server (Linux Apache MySQL PHP)
- PhpMyAdmin - ArchWiki article covering the web-based tool to help manage MySQL databases using an Apache/PHP front-end.
- PHP - ArchWiki article on PHP.
- MySQL Performance Tuning Scripts and Know-How