Docker Compose Setup

In this example the Database container is configured through Docker compose
Make sure to mount a directory that will contain the backups, in this case we mount ./db_backup to /var/mariadb/backup in the container

This is a part of a larger docker-compose.yml

        
db:
image: mariadb:10
restart: always
volumes:
    - ./data:/var/lib/mysql
    - ./db_backup:/var/mariadb/backup
    - ./config/db:/etc/mysql/conf.d
environment:
    MARIADB_ROOT_PASSWORD: password
    MARIADB_DATABASE: my_db
        
    

Backup Script

Next Lets create a backup script. This script will be somewhat generic and should work on both docker and native running instances of MySQL or MariaDB
The Script assumes the password is stored in MARIADB_ROOT_PASSWORD environment variable, which is common for docker setups

        
#!/bin/bash
sql_pw=$(printenv MARIADB_ROOT_PASSWORD)
backup_dir=/var/mariadb/backup
How many days to keep backup for
keep_for_days=5
logfile=$backup_dir/backup.log
backup_file=$backup_dir/full-db-dump-$(date +%Y-%m-%d_%H-%M-%S).sql.gz
echo "$(date +%Y-%m-%d_%H-%M-%S) Backup Start" >> $logfile
#dump DB and compress with gzip
mysqldump --all-databases -uroot -p$sql_pw | gzip >> $backup_file
if [ $? == 0 ]; then
echo "$(date +%Y-%m-%d_%H-%M-%S) sql backup done" >> $logfile
else
echo [error] mysqldump returned error code $? >> $logfile
fi
Delete old backups
find $backup_dir -mtime +$keep_for_days -delete

run_backup.sh

Now we need a script that will copy and execute the backup script in the DB docker container
seperating the two scripts makes the first more generic and easier to write

#!/bin/bash
docker cp /full_path_to_script/run_backup.sh db-container-name:/tmp/run_backup.sh
docker exec db-container-name ./tmp/run_backup.sh

docker_run_backup.sh

Add Script To Crontab

Lastly we just need to add docker_run_backup.sh to roots crontab so that we have a periodic backup
run

        
sudo crontab -e
        
    

And then add the following line to your crontab file, this will run our script every day at midnight

        
0 0 * * * /path_to_script/docker_run_backup.sh
        
    

You now have your Docker MariaDB Container backing up every night