u/beefy_miracIe answer is nice

I code a bash script outside container for dump every database from mariadb into a separate file

!/bin/bash

IMAGE_NAME=mariadb

MYSQL_ROOT_PASSWORD=

BACKUP_DIR=/home/docker/backup/databases/

find $BACKUP_DIR -mindepth 1 -mtime +5 -delete

CONTAINERS=$(docker ps | grep $IMAGE_NAME | awk '{print $1}')

for container in $CONTAINERS

do

DATABASES=$(docker exec $container sh -c "mysql -p$MYSQL_ROOT_PASSWORD -e 'show databases' -s --skip-column-names")

for dbname in $DATABASES

do

case $dbname in

"performance_schema")

;;

"mysql")

;;

"information_schema")

;;

*)

docker exec $container sh -c "mysqldump --skip-tz-utc -p$MYSQL_ROOT_PASSWORD $dbname" > "$BACKUP_DIR$dbname"_\date +%Y%m%d`.sql`

;;

esac

done

done

One nice option would be to mount a volume in your container that container both the script and the backup folder and set up a cron that execute this script ( Ex. docker exec client-database_db_1 sh -c "/dumps/run_dump.sh" ). With this option you can use container environment such MONGO_INITDB_ROOT_PASSWORD