How to Use the MySQL Images
Start a MySQL Server Instance
Start a MySQL instance as follows (but make sure you also read the sections Secure Container Startup and Where to Store Data below):
docker run --name my-container-name -e MYSQL_ROOT_PASSWORD=my-secret-pw -d diceone/docker_mysql-5.5:tag
my-container-name is the name you want to assign to your container,
my-secret-pw is the password to be set for the MySQL root user and
tag is the tag specifying the MySQL version you want. See the list above for relevant tags, or look at the full list of tags.
Connect to MySQL from an Application in Another Docker Container
This image exposes the standard MySQL port (3306), so container linking makes the MySQL instance available to other application containers. Start your application container like this in order to link it to the MySQL container:
docker run --name app-container-name --link my-container-name:mysql -d app-that-uses-mysql
Connect to MySQL from the MySQL Command Line Client
The following command starts another MySQL container instance and runs the
mysql command line client against your original MySQL container, allowing you to execute SQL statements against your database:
docker run -it --link my-container-name:mysql --rm mysql/mysql-server:tag sh -c 'exec mysql -h"$MYSQL_PORT_3306_TCP_ADDR" -P"$MYSQL_PORT_3306_TCP_PORT" -uroot -p"$MYSQL_ENV_MYSQL_ROOT_PASSWORD"'
my-container-name is the name of your original MySQL Server container.
More information about the MySQL command line client can be found in the MySQL reference documentation at http://dev.mysql.com/doc/refman/en/
Container Shell Access and Viewing MySQL Log Files
docker exec command allows you to run commands inside a Docker container. The following command line will give you a bash shell inside your MySQL container:
docker exec -it my-container-name bash
The MySQL Server log is located at
/var/log/mysqld.log inside the container, and the following command line from a shell inside the container will let you inspect it:
When you start the MySQL image, you can adjust the configuration of the MySQL instance by passing one or more environment variables on the
docker run command line. Do note that none of the variables below will have any effect if you start the container with a data directory that already contains a database: any pre-existing database will always be left untouched on container startup.
Most of the variables listed below are optional, but one of the variables
MYSQL_RANDOM_ROOT_PASSWORD must be given.
This variable specifies a password that will be set for the MySQL root superuser account. In the above example, it was set
to my-secret-pw. NOTE: Setting the MySQL root user password on the command line is insecure. See the section Secure Container Startup below for an alternative.
When this variable is set to
yes, a random password for the server's root user will be generated. The password will be printed to stdout in the container, and it can be obtained by using the command
docker logs my-container-name.
This variable is optional. When set to
yes, the root user's password will be set as expired, and must be changed before MySQL can be used normally. This is only supported by MySQL 5.6 or newer.
This variable is optional. It allows you to specify the name of a database to be created on image startup. If a user/password was supplied (see below) then that user will be granted superuser access (corresponding to GRANT ALL) to this database.
These variables are optional, used in conjunction to create a new user and set that user's password. This user will be granted superuser permissions (see above) for the database specified by the
MYSQL_DATABASE variable. Both variables are required for a user to be created.
Do note that there is no need to use this mechanism to create the
root superuser, that user gets created by default with the password set by either of the mechanisms (given or generated) discussed above.
yes to allow the container to be started with a blank password for the root user. NOTE: Setting this variable to
yes is not recommended unless you really know what you are doing, since this will leave your MySQL instance completely unprotected, allowing anyone to gain complete superuser access.
Notes, Tips, Gotchas
Secure Container Startup
In many use cases, employing the
MYSQL_ROOT_PASSWORD variable to specify the MySQL root user password on initial container startup is insecure. Instead, to keep your setup as secure as possible, we strongly recommend using the
MYSQL_RANDOM_ROOT_PASSWORD option. To further secure your instance, we also recommend using the
MYSQL_ONETIME_PASSWORD variable if you use MySQL version 5.6 or higher.
This is the full procedure:
docker run --name my-container-name -e MYSQL_RANDOM_ROOT_PASSWORD=yes -e MYSQL_ONETIME_PASSWORD=yes -d mysql/mysql-server:tag docker logs my-container-name
Look for the "GENERATED ROOT PASSWORD" line in the output.
If you also set the
MYSQL_ONETIME_PASSWORD variable, you must now start a bash shell inside the container in order to set a new root password:
docker exec -it my-container-name bash
Start the MySQL command line client and log in using the randomly set root password:
mysql -u root -p
And finally, on the mysql client command line, set a new, secure root password for MySQL:
ALTER USER root IDENTIFIED BY 'my-secret-pw';
Where to Store Data
There are basically two ways to store data used by applications that run in Docker containers. We encourage users of MySQL with Docker to familiarize themselves with the options available, including:
- Let Docker manage the storage of your database data by writing the database files to disk on the host system using its own internal volume management. This is the default and is easy and fairly transparent to the user. The downside is that the files may be hard to locate for tools and applications that run directly on the host system, i.e. outside containers.
- Create a data directory on the host system (outside the container) and mount this to a directory visible from inside the container. This places the database files in a known location on the host system, and makes it easy for tools and applications on the host system to access the files. The downside is that the user needs to make sure that the directory exists, and that e.g. directory permissions and other security mechanisms on the host system are set up correctly.
The Docker documentation is a good starting point for understanding the different storage options and variations, and there are multiple blog and forum postings that discuss and give advice in this area. We will simply show the basic procedure here for the latter option above:
- Create a data directory on a suitable volume on your host system, e.g.
- Start your MySQL container like this:
docker run --name my-container-name -v /my/own/datadir:/var/lib/mysql -e MYSQL_ROOT_PASSWORD=my-secret-pw -d mysql/mysql-server:tag
-v /my/own/datadir:/var/lib/mysql part of the command mounts the
/my/own/datadir directory from the underlying host system as
/var/lib/mysql inside the container, where MySQL by default will write its data files.
Note that users on systems with SELinux enabled may experience problems with this. The current workaround is to assign the relevant SELinux policy type to the new data directory so that the container will be allowed to access it:
chcon -Rt svirt_sandbox_file_t /my/own/datadir
Usage Against an Existing Database
If you start your MySQL container instance with a data directory that already contains a database (specifically, a
mysql subdirectory), the
$MYSQL_ROOT_PASSWORD variable should be omitted from the
docker run command line; it will in any case be ignored, and the pre-existing database will not be changed in any way.
Docker allows mapping of ports on the container to ports on the host system by using the -p option. If you start the container as follows, you can connect to the database by connecting your client to a port on the host machine, in this example port 6603:
docker run --name my-container-name -p 6603:3306 -d mysql/mysql-server
Passing options to the server
You can pass arbitrary command line options to the MySQL server by appending them to the
docker run --name my-container-name -d mysql/mysql-server --option1=value --option2=value
In this case, the values of option1 and option2 will be passed directly to the server when it is started. The following command will for instance start your container with UTF-8 as the default setting for character set and collation for all databases in MySQL:
docker run --name my-container-name -d mysql/mysql-server --character-set-server=utf8 --collation-server=utf8_general_ci
Using a Custom MySQL Config File
The MySQL startup configuration in these Docker images is specified in the file
/etc/my.cnf. If you want to customize this configuration for your own purposes, you can create your alternative configuration file in a directory on the host machine and then mount this file in the appropriate location inside the MySQL container, effectively replacing the standard configuration file.
If you want to base your changes on the standard configuration file, start your MySQL container in the standard way described above, then do:
docker exec -it my-container-name cat /etc/my.cnf > /my/custom/config-file
... where ´/my/custom/config-file´ is the path and name of the new configuration file. Then start a new MySQL container like this:
docker run --name my-new-container-name -v /my/custom/config-file:/etc/my.cnf -e MYSQL_ROOT_PASSWORD=my-secret-pw -d mysql/mysql-server:tag
This will start a new MySQL container ´my-new-container-name´ where the MySQL instance uses the startup options specified in ´/my/custom/config-file´.
Note that users on systems where SELinux is enabled may experience problems with this. The current workaround is to assign the relevant SELinux policy type to your new config file so that the container will be allowed to mount it:
chcon -Rt svirt_sandbox_file_t /my/custom/config-file
Docker Optimized MySQL Install
These Docker images are optimized for size, which means that we have reduced the contents to what is expected to be relevant for a large majority of users who run Docker based MySQL instances. The key differences compared to a default MySQL install are:
- All binaries are stripped, non-debug only
- Included binaries are limited to:
/usr/bin/my_print_defaults /usr/bin/mysql /usr/bin/mysql_config /usr/bin/mysql_install_db /usr/bin/mysql_tzinfo_to_sql /usr/bin/mysql_upgrade /usr/bin/mysqldump /usr/sbin/mysqld