ebspace/armhf-mysql repository overview

⁠ARMHF MySQL

Build Source : https://github.com/haotseng/armhf_dockerfiles⁠

⁠How to build image :

docker build -t ebspace/armhf-mysql:latest .

⁠How to Use the MySQL Images

⁠Start a MySQL Server Instance

Start a MySQL instance as follows :

docker run --name my-container-name -e MYSQL_ROOT_PASSWORD=my-secret-pw -d ebspace/armhf-mysql:latest

... where 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.

⁠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 ebspace/armhf-mysql:latest sh -c 'exec mysql -h"$MYSQL_PORT_3306_TCP_ADDR" -P"$MYSQL_PORT_3306_TCP_PORT" -uroot -p"$MYSQL_ENV_MYSQL_ROOT_PASSWORD"'

... where 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

The 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 /bin/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:

more /var/log/mysqld.log

⁠Environment Variables

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_ROOT_PASSWORD, MYSQL_ALLOW_EMPTY_PASSWORD, MYSQL_RANDOM_ROOT_PASSWORD must be given.

⁠MYSQL_ROOT_PASSWORD

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.

As an alternative to specifying the password explicitly, if the variable is set to a file path, the contents of the file will be used as the root password.

⁠MYSQL_RANDOM_ROOT_PASSWORD

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.

⁠MYSQL_DATABASE

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.

⁠MYSQL_USER, MYSQL_PASSWORD

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.

⁠MYSQL_ALLOW_EMPTY_PASSWORD

Set to 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

⁠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:

1. Create a data directory on a suitable volume on your host system, e.g. /my/own/datadir.

2. 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 ebspace/armhf-mysql:latest

The -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.

⁠Port forwarding

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 ebspace/armhf-mysql:latest

⁠Passing options to the server

You can pass arbitrary command line options to the MySQL server by appending them to the run command:

docker run --name my-container-name -d ebspace/armhf-mysql:latest --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 ebspace/armhf-mysql:latest --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/mysql/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/mysql/my.cnf -e MYSQL_ROOT_PASSWORD=my-secret-pw -d ebspace/armhf-mysql:latest

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.