How to Back Up Your Docker Volumes

Docker volumes are applied to shop persistent knowledge individually from your containers. Info that is stored in a quantity stays obtainable right after your containers stop, making it possible for you to containerize stateful workloads.

Whilst volumes outlive containers, this isn’t sufficient protection for generation programs. You need to again up your volumes so you can get better them after a catastrophe. Developing standard quantity backups guarantees you are in a position to restore your atmosphere if your Docker host is compromised or knowledge is unintentionally deleted.

Managing Volume Backups

Docker does not have a created-in system for backing up volumes or exporting their contents. You need to have to established up your have remedy to obtain the volume and duplicate its information to your backup place.

Generating a temporary container that mounts the quantity you will need to back again up is ordinarily the most straightforward way to move forward. Incorporate the --volumes-from flag to a docker operate command to instantly mount an existing container’s volumes into your backup container. You can then use tools such as tar and gzip to deposit an archive of the volume’s written content into your operating listing.

Here’s a finish illustration of this procedure:

# Produce a container that merchants knowledge in the "mysql_facts" volume
docker run -d 
    --name mysql 
    -v mysql_data:/var/lib/mysql 
    -e MYSQL_ROOT_PASSWORD=mysql 
    mysql:8

# Begin a temporary container to back up the "mysql_info" volume
docker operate --rm 
    --volumes-from mysql
    -v $PWD:/backup-dir 
    ubuntu tar cvf /backup-dir/mysql-backup.tar /var/lib/mysql

The --volumes-from flag indicates the non permanent backup container gets obtain to the mysql container’s volumes. The /var/lib/mysql directory within the backup container exposes the volume’s information mainly because this is the route employed by the mysql container. Tarring the path will generate an archive of your volume that you can use as a backup. It receives deposited into your operating listing since of the bind mount that is established up by the -v flag.

The --rm flag will take out the backup container as soon as the command completes. This leaves the archive in your operating directory, completely ready to be moved to extended-term storage. You can automate backup development by including the docker run command as a cron process.

Restoring Your Backup

You can use a very similar technique to restore your backup. When you are replacing the contents of an present quantity, build yet another momentary container with the quantity and a bind mount to your backup archive. Extract the contents of the archive into the volume’s mount path.

$ docker run --rm 
    --volumes-from mysql
    -v $PWD:/backup-dir
    bash -c "cd /var/lib/mysql && tar xvf /backup-dir/mysql-backup.tar"

This can be risky if containers are actively making use of the volume. Overwriting files that are in use could induce errors and unexpected habits. You can use the docker prevent command to temporarily halt your containers just before bringing them again up with docker begin.

$ docker prevent mysql

# Restore the backup
# ...

$ docker start off mysql

Develop the volume before you start off your container if you’re restoring a backup to a new host:

$ docker volume generate new_quantity

Then mount this quantity to your temporary container:

docker run --rm 
    -v new_quantity:/var/lib/mysql
    -v $PWD:/backup-dir 
    ubuntu tar cvf /backup-dir/mysql-backup.tar /var/lib/mysql

Commencing your application container with the identical volume will offer access to the files you’ve restored:

docker run -d 
    --title mysql 
    -v new_volume:/var/lib/mysql 
    -e MYSQL_ROOT_PASSWORD=mysql 
    mysql:8

Testing these techniques lets you test your backups will be usable if you at any time facial area a disaster.

Backing Up Volumes Directly

The process outlined over is the recommended way to again up Docker volumes. Even so some predicaments could be far better served by directly copying written content from exactly where volumes are stored on your host’s filesystem.

You will usually come across the material of your volumes in /var/lib/docker/volumes. Each individual volume receives its possess subdirectory, these kinds of as /var/lib/docker/volumes/mysql. Inside this top rated-stage route you will obtain a _information folder which includes all the files saved inside the quantity.

Archiving the /var/lib/docker/volumes listing can be a convenient way to rapidly backup almost everything on your host. You will require to use sudo however simply because anything less than this path is owned by root.

Backing up volumes in this way is not advisable for normal use since it’s not moveable throughout installations. Docker’s quantity driver procedure usually means volume information won’t automatically be stored on your host’s filesystem – it could be on a community share or an additional distant area. This method really should only be attempted when you want a fast backup before you run servicing on a precise machine.

Summary

Docker volumes require to be treated with treatment mainly because they incorporate your application’s persistent knowledge. Producing common back again ups will shield you from information loss in situation your host is compromised or an errant container approach deletes data files by miscalculation.

Even though you can develop backups by archiving Docker’s installation listing, this should be averted wherever attainable. Short-term backup containers may possibly feel cumbersome but they can be easily scripted and deliver predictable outcomes throughout volume motorists.

The moment you have produced a volume backup archive, bear in mind to add it to distant storage as quickly as possible. A backup stored on the machine it originates from will be no enable if you reduce accessibility or a components failure occurs.