Configuring MariaDB with my.cnf

The my.cnf file allows you to configure MariaDB to run the way you want it. Most of the server system variables can be set in the my.cnf file, although usually only a few are, and the rest simply take their default values.

Depending on how you've installed MariaDB, the my.cnf may be in a number of places, or it may not exist at all.

Location in Linux, Unix, Mac

On a Linux, Unix or Mac server, MariaDB looks for the my.cnf file in the following locations:

• MYSQL_HOME is the environment variable containing the path to the directory holding the server-specific my.cnf file. If MYSQL_HOME is not set, and the server is started with mysqld_safe, MYSQL_HOME is set as follows:
  • If there is a my.cnf file in the MariaDB data directory, but not in the MariaDB base directory, MYSQL_HOME is set to the MariaDB data directory.
  • Else, MYSQL_HOME is set to the MariaDB base directory.

Location in Windows

On Windows, my.ini can be used as well as my.cnf, and MariaDB looks in the following locations.

• %WINDIR% is the Windows directory, usually C:\WINDOWS. To find its specific value on your system, use:

  C:\> echo %WINDIR%

• INSTALLDIR is a directory, one level up from mysqld.exe, for example, C:\Program Files\MariaDB 10.1.
• MYSQL_HOME is the environment variable containing the path to the directory holding the server-specific my.cnf file.

my.cnf hierarchy

MariaDB will look in all of the above locations, in order, even if has already found a my.cnf file, and it's possible for more than one my.cnf file to exist. For example, you can have a my.cnf file in /etc/mysql/my.cnf with global settings for all servers, and then another my.cnf file in the user's home directory, ~/my.cnf, which will add further (or overwrite) settings specific only to that user.

Note that if the --defaults-file option is used, only this file will be read (client programs will also read .mylogin.cnf when using the --defaults-file option). If the file does not exist, an error will occur.

If no my.cnf file is found, the default values are used for all variables. See server system variables for a full list of all server variables and their default values.

You will most likely also find a sample my.cnf file called my-default.cnf, or, on older releases, my-huge.cnf.sh, my-large.cnf.sh, my-medium.cnf.sh, and my-small.cnf.sh (these are now very dated for modern servers). You can choose one of these appropriate for your type of installation, and copy and use as the basis for your my.cnf file.

Configuration syntax and groups

The syntax of the MariaDB and MySQL configuration files are:

• Lines starting with # are comments.
• Empty lines are ignored.
• A group starts with the syntax [group-name]
• You may have many instances of the same group.
• !include filename can be used to include other configuration files.
• !includedir directory can be used to include all configuration files in a given directory. Note that the files are read in alphabetical order.
• Options prefixed by loose will not produce an error if they don't exist.

A MariaDB / MySQL program can read one or many groups. You can see for each program which configuration files and groups it reads by executing program-name --help --verbose

sh> mysqld --help --verbose

./mysqld  Ver 10.2.1-MariaDB-valgrind-max-debug for Linux on x86_64 (Source distribution)
Copyright (c) 2000, 2016, Oracle, MariaDB Corporation Ab and others.

Starts the MariaDB database server.

Usage: ./mysqld [OPTIONS]

Default options are read from the following files in the given order:
/etc/my.cnf /etc/mysql/my.cnf ~/.my.cnf 
The following groups are read: mysqld server mysqld-10.2 mariadb mariadb-10.2 client-server galera
....

The configuration files are scanned once, in the order given by --help --verbose. The effect of the configuration options are as if they would have been given as command line options in the order they are found.

You can check which command line optiond a given program is going to use by starting it with the option --print-defaults or using the my_print_defaults program.

sh> ./client/mysqldump --print-defaults
./client/mysqldump would have been started with the following arguments:
--socket=/tmp/mysql-dbug.sock --port=3307 --quick --max_allowed_packet=16M 

sh> my_print_defaults mysqldump
--quick
--max_allowed_packet=16M

All MariaDB programs read, in addition to the common groups, the group with the same name as the program. For example mysqldump reads the group [mysqldump].

The following general groups are recognized:

By using the mysqld-version syntax, one can create configuration files that will work for both MariaDB and MySQL!

Example of configuration file

The following is an extract of a configuration that one can use if one wants to work with both MySQL and MariaDB.

# Example mysql config file.

[client-server]
socket=/tmp/mysql-dbug.sock
port=3307

# This will be passed to all mysql clients
[client]
password=my_password

# Here are entries for some specific programs
# The following values assume you have at least 32M ram

# The MySQL server
[mysqld]
temp-pool
key_buffer_size=16M
datadir=/my/mysqldata
loose-innodb_file_per_table

[mariadb]
datadir=/my/data
default-storage-engine=aria
loose-mutex-deadlock-detector
max-connections=20

[mariadb-5.5]
language=/my/maria-5.5/sql/share/english/
socket=/tmp/mysql-dbug.sock
port=3307

[mariadb-10.1]
language=/my/maria-10.1/sql/share/english/
socket=/tmp/mysql2-dbug.sock

[mysqldump]
quick
max_allowed_packet=16M

[mysql]
no-auto-rehash
loose-abort-source-on-error

You can find some example configuration files, like my-large.cnf, in the support-files or /usr/share/mysql/mysql directory, depending on your installation.