How to back up MariaDB databases running in a container

How to back up MariaDB databases running in a container

docker backup mariadb

Backups are sometimes not quite present in our everyday life, but if we suddenly face a problem there is nothing but a backup that can save us.

In the past, I have mounted the data from MariaDB (or MySQL) containers using Docker on a specific Docker volume and backed it up daily.

Depending on the database engine, this data may or may not be consistent. For an installation that has a very large database workload, such backups are almost never consistent and are therefore not an optimal solution.

We want to make sure that we can restore a complete backup of the database in case of a disaster.

How to back up MariaDB databases running in a container

In the following article I will use the MariaDB container from linuxserver.io.

The great thing about linuxserver.io’s containers is that we can extend them with a simple cron mod without having to manually build a container.

docker-compose.yml for MariaDB

---
version: "2"
services:
  db:
    image: linuxserver/mariadb
    environment:
      - PUID=1000
      - PGID=1000
      - MYSQL_ROOT_PASSWORD=5KZjsGqb3j64it3iFAMv
      - TZ=Europe/London
      - MYSQL_DATABASE=somedatabase
      - MYSQL_USER=someuser
      - MYSQL_PASSWORD=WmaZmg450vrU2Hq7nMYe
      - DOCKER_MODS=linuxserver/mods:universal-cron
    volumes:
      - ./db:/config
    restart: unless-stopped

You need to change MYSQL_ROOT_PASSWORD, MYSQL_DATABASE, MYSQL_USER and MYSQL_PASSWORD according to your setup.

The most important part is the activation of the universal-cron Docker mod via the environment variable DOCKER_MODS. Now we can set up our own backup cron.

MariaDB Backup Cron

In our docker-compose.yml we mount the /config volume to the db directory.

Now we need to start our container for the first time so that all necessary data is created and the mount point is created.

docker compose up -d

Next we move to the folder db and create a new folder here named backups.

Then we open the following file with an editor: vim db/crontabs/root

Here we now add our MariaDB container backup cron. In my example the backup is executed daily at 10:30. Of course you can adjust this value on your own. You can find help with cronjobs for example at crontab.guru .

30 10 * * * mysqldump -u someuser -pPASSWORD somedatabase > /config/backups/todays-db-backup.sql

The file should look like this. Please include your username, database name and the password of the database in the command.

# do daily/weekly/monthly maintenance
# min   hour    day month   weekday command
*/15    *   *   *   *   run-parts /etc/periodic/15min
0   *   *   *   *   run-parts /etc/periodic/hourly
0   2   *   *   *   run-parts /etc/periodic/daily
0   3   *   *   6   run-parts /etc/periodic/weekly
0   5   1   *   *   run-parts /etc/periodic/monthly
30 10 * * * mysqldump -u someuser -pPASSWORD somedatabase > /config/backups/todays-db-backup.sql

Save the file and restart the database container once:

docker compose down
docker compose up -d

From now on, a MySQL dump of our MariaDB database will be created every day at 10:30am.

Remember to back up this mysql dump daily with a backup tool of your choice, as it will be automatically overwritten with the latest backup every day at 10:30.

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