Use Named Volume For Persistent Data (MySQL)

In this log, I record the steps of making named volume for persistent data and make some necessary notes about it.

I use MySQL as database in the case.

{ } wraps the custom variable.

Create a Named Volume

docker volume create --name {volume_name}

Create a Defined Network for Combining Containers

docker network create {network_name}

Create a MySQL Container

Create and connect to the specified network you’ve just created:

docker run -d --rm --name {mysql_container_name} -v {volume_name}:/var/lib/mysql -p {new_mysql_port}:3306 -e MYSQL_ROOT_PASSWORD={your_mysql_root_password} --network {network_name} mysql:tag

MySQL data directory: /var/lib/mysql
--daemon, -d: Run container in background and print container ID.
--rm: Automatically remove the container when it exits.
--volume, -v: To use volume.
--publish, -p: Map port for MySQL. The default is 3306. You should specify another one for multiple MySQL containers.
--env, -e: Set the environment (root password) for MySQL: -e MYSQL_ROOT_PASSWORD={password}

Create a PhpMyAdmin Container for MySQL Container

I use a PhpMyAdmin container as the front-end database management of the MySQL container. So we need combine these two containers.

There’re two methods:

Link (A Legacy Feature)

docker run --rm --name {phpmyadmin_container_name} --link {mysql_contain_name}:{alias_name} -p {new_phpmyadmin_port}:80 phpmyadmin/phpmyadmin

--link: Add link to MySQL container.

This feature is deprecated by Docker. Don’t use it.

User Defined Network

Usage:

docker network connect {network} {container}

Create and connect to the specified network:

docker run -d --rm --name {phpmyadmin_container_name} --network {network_name} -p {new_phpmyadmin_port}:80 -e PMA_HOST={mysql_container_name} phpmyadmin/phpmyadmin

--network, --net: Connect a container to a network.

Use Your PhpMyAdmin

Open browser, visit http://localhost:{new_phpmyadmin_port}.

You might get the login error:

The server requested authentication method unknown to the client.

It is because MySQL uses the auth_socket (>= v5.7) or caching_sha2_password (>= 8.0) plugin as the authentication method for root user. For logining the PhpMyAdmin, you should change the password with mysql_native_password plugin or create a new user.

Use MySQL to Deal With Admin Account

Enter MySQL container’s bash:

docker exec -it {mysql_container_name} bash

Enter MySQL cli:

mysql -u root -p{password}

You can change root’s password:

alter user 'root'@'localhost' identified with mysql_native_password BY {'password'};
flush privileges;

Or create a new admin account:

create user {'username'@'host'} identified with mysql_native_password by {'password'};
grant all privileges on {database} to {'username'@'server'};
flush privileges;

{'username'@'host'}: ‘host’ could be ‘localhost’ or ‘%’. ‘%’ means the account can be accessed from any ip.
{database}: *.* means all.

Backup Named Volume

First, create a new container (based on a tiny image like busybox) with the data volume mounted. The data var/lib/mysql as the volume mapped data will be mounted to the new container. Then we will tar it in the new container for backup. For getting the tar file in our local host, we mount a local directory as another volume for the new container’s data backup.

docker run --rm --volumes-from {mysql_container_name} -v $(pwd):/backup busybox tar cvf /backup/{backup_file_name}.tar /var/lib/mysql

--volumes-from: Mount volumes from the specified container(s).
$(pwd): Print the name of the current Working Directory.

Restore container from backup

Mount data volume and backup directory to a temporary container. Then, untar the backup file to replace files in the data volume:

docker run --rm --volumes-from {mysql_container_name} -v $(pwd):/backup centos bash -c "cd /var/lib && rm -rf mysql/* && tar xvf /backup/{backup_file_name}.tar --strip 2"

For PowerShell, use ${pwd} instead of $(pwd).

Restart the MySQL container to make the restored data works:

docker restart {mysql_container_name}

To be continued

I will keep finding an easier and smarter way.