MySQL is a widely spread, multi-threaded, multi-user SQL database. For more information about features, see the official homepage.
- 1 Installation
- 2 Configuration
- 3 Database maintenance
- 4 Backup
- 5 Troubleshooting
- 5.1 MySQL daemon cannot start
- 5.2 Unable to run mysql_upgrade because MySQL cannot start
- 5.3 Reset the root password
- 5.4 Check and repair all tables
- 5.5 Optimize all tables
- 5.6 OS error 22 when running on ZFS
- 5.7 Cannot login through CLI, but phpmyadmin works well
- 5.8 MySQL binary logs are taking up huge disk space
- 6 See also
Alternative implementations are:
- Oracle MySQL — An implementation by Oracle Corporation.
- https://www.mysql.com/ || AUR
- Percona Server — An implementation by Percona LLC.
# mysql_install_db --user=mysql --basedir=/usr --datadir=/var/lib/mysql
mariadb.service can be started and/or enabled with systemd.
The following command will interactively guide you through a number of recommended security measures at the database level:
Upgrade from Oracle MySQL to MariaDB
See the announcement for the procedure to follow.
Once you have started the MySQL server and added a root account, you may want to change the default configuration.
To log in as
root on the MySQL server, use the following command:
$ mysql -u root -p
Creating a new user takes two steps: create the user; grant privileges. In the below example, the user monty with some_pass as password is being created, then granted full permissions to the database mydb:
$ mysql -u root -p
MariaDB> CREATE USER 'monty'@'localhost' IDENTIFIED BY 'some_pass'; MariaDB> GRANT ALL PRIVILEGES ON mydb.* TO 'monty'@'localhost'; MariaDB> FLUSH PRIVILEGES; MariaDB> quit
MariaDB configuration options are read from the following files in the given order (according to
mysqld --help --verbose output):
/etc/my.cnf /etc/mysql/my.cnf ~/.my.cnf
Depending on the scope of the changes you want to make (system-wide, user-only...), use the corresponding file. See this entry of the KnowledgeBase for more information.
Grant remote access
If you want to access your MySQL server from other LAN hosts, you have to edit the following lines in
[mysqld] ... #skip-networking bind-address = <some ip-address> ...
Grant any MySQL user remote access (example for root):
$ mysql -u root -p
Check current users with remote access privileged:
SELECT User, Host FROM mysql.user WHERE Host <> 'localhost';
Now grant remote access for your user (here root)::
GRANT ALL PRIVILEGES ON *.* TO 'root'@'192.168.1.%' IDENTIFIED BY 'my_optional_remote_password' WITH GRANT OPTION;
You can change the '%' wildcard to a specific host if you like. The password can be different from user's main password.
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
You will still be able to log in from the localhost.
The MySQL client completion feature is disabled by default. To enable it system-wide edit
/etc/mysql/my.cnf, and replace
auto-rehash. Completion will be enabled next time you run the MySQL client.
/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
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
tmpdir = /var/lib/mysqltmp
Then reboot or ( shutdown mysql, mount the tmpdir, start mysql ).
Time zone tables
Although time zone tables are created during the installation, they are not automatically populated. They need to be populated if you are planning on using CONVERT_TZ() in SQL queries.
To populate the time zone tables with all the time zones:
$ mysql_tzinfo_to_sql /usr/share/zoneinfo | mysql -u root -p mysql
Optionally, you may populate the table with specific time zone files:
$ mysql_tzinfo_to_sql <timezone_file> <timezone_name> | mysql -u root -p mysql
Upgrade databases on major releases
Upon a major version release of(for example mariadb-10.1.10-1 to mariadb-10.1.18-1), it is wise to upgrade databases:
$ mysql_upgrade -u root -p
Checking, optimizing and repairing databases
mysqlcheck which can be used to check, repair, and optimize tables within databases from the shell. See the mysqlcheck man page for more. Several command tasks are shown:
To check all tables in all databases:
$ mysqlcheck --all-databases -u root -p -c
To analyze all tables in all databases:
$ mysqlcheck --all-databases -u root -p -a
To repair all tables in all databases:
$ mysqlcheck --all-databases -u root -p -r
To optimize all tables in all databases:
$ mysqlcheck --all-databases -u root -p -o
There are various tools and strategies to back up your databases.
If you are using the default InnoDB storage engine, a suggested way of backing up all your bases online while provisioning for point-in-time recovery (also known as “roll-forward,” when you need to restore an old backup and replay the changes that happened since that backup) is to execute the following command:
$ mysqldump --single-transaction --flush-logs --master-data=2 --all-databases -u root -p > all_databases.sql
This will prompt for MariaDB's root user's password, which was defined during database #Configuration.
Specifying the password on the command line is strongly discouraged, as it exposes it to discovery by other users through the use of
ps aux or other techniques. Instead, the aforementioned command will prompt for the specified user's password, concealing it away.
As SQL tables can get pretty large, it is recommended to pipe the output of the aforementioned command in a compression utility like:
$ mysqldump --single-transaction --flush-logs --master-data=2 --all-databases -u root -p | gzip > all_databases.sql.gz
Decompressing the backup thus created and reloading it in the server is achieved by doing:
$ gunzip all_databases.sql.gz | mysql -u root -p
Basically you should add the following section to the relevant configuration file:
[mysqldump] user=mysqluser password=secret
Mentioning a user here is optional, but doing so will free you from having to mention it on the command line.
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
A python-based software package named Holland Backup is available in AUR to automate all of the backup work. It supports direct mysqldump, LVM snapshots to tar files (mysqllvm), LVM snapshots with mysqldump (mysqldump-lvm), and methods to extract the data. The Holland framework supports a multitude of options and is highly configurable to address almost any backup situation.
/usr/share/doc/holland/examples/ directory and can be copied to
/etc/holland/backupsets/, as well as using the
holland mk-config command to generate a base config for a named provider.
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/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
# cp /etc/mysql/my.cnf /etc/my.cnf
Now try and start the daemon.
If you get these messages in your
[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/
If you have datadir in /home /root or /run/user or a subdirectory of those, from 10.1.16 onwards, due to enhanced security, you need to move your datadir to a path or edit
mysqld.service to change the default
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
mariadb.service. 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> use mysql; mysql> UPDATE mysql.user SET Password=PASSWORD('MyNewPass') WHERE User='root'; mysql> FLUSH PRIVILEGES; mysql> exit
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
However, if the post install scripts failed because of the above issue, MySQL/MariaDB might be in an invalid state. To recover from this state, execute the following:
rm -rf /var/lib/mysql/* mysql_install_db --user=mysql --basedir=/usr --datadir=/var/lib/mysql chown -R mysql:mysql /var/lib/mysql &>/dev/null /usr/bin/systemd-tmpfiles --create mysql.conf
After which MySQL/MariaDB should be installed correctly.
Cannot login through CLI, but phpmyadmin works well
This may happen if you are using a long (>70-75) password. As for 5.5.36, for some reason, mysql CLI cannot handle that much characters in readline mode. So, if you are planning to use the recommended password input mode:
$ mysql -u <user> -p Password:
consider changing the password to smaller one.
MySQL binary logs are taking up huge disk space
By default, mysqld creates binary log files in
/var/lib/mysql. This is useful for replication master server or data recovery. But these binary logs can eat up your disk space. If you do not plan to use replication or data recovery features, you may disable binary logging by commenting out these lines in
Or you could limit the size of the logfile like this:
expire_logs_days = 10 max_binlog_size = 100M
Alternatively, you can purge some binary logs in
/var/lib/mysql to free up disk space with this command:
# mysql -u root -p"PASSWORD" -e "PURGE BINARY LOGS TO 'mysql-bin.0000xx';"