Volume management

Learn to manage volumes with docker volume ls and rm.

Volume management

The docker volume subcommands:

docker volume ls                 # list
docker volume inspect pgdata     # details: Mountpoint, creation
docker volume rm pgdata          # delete (no container must use it)
docker volume prune              # delete anonymous volumes no container uses
docker volume prune -a           # also the unused named ones

Deleting a volume can't be undone; take a backup first for database volumes.

Backing up a volume

The standard way to back up a volume is to mount it and a host folder into a temporary container and create a tar archive:

docker run --rm -v pgdata:/veri:ro -v "$PWD":/yedek alpine \
  tar czf /yedek/pgdata.tar.gz -C /veri .

# restoring
docker run --rm -v pgdata:/veri -v "$PWD":/yedek alpine \
  tar xzf /yedek/pgdata.tar.gz -C /veri

Copying a running database's files can be inconsistent; the database should also be backed up with its own tools (pg_dump).

Exercise A volume backup

Write two commands: list the volumes; then in an alpine container deleted when done, mount pgdata read-only at /veri and the current folder ("$PWD") at /yedek, and run tar czf /yedek/pgdata.tar.gz -C /veri .

Show example solution

docker volume ls
docker run --rm -v pgdata:/veri:ro -v "$PWD":/yedek alpine tar czf /yedek/pgdata.tar.gz -C /veri .

Test yourself

After docker rm -f db, what happens to the pgdata volume db had mounted?
- It is added to the image
- It gets corrupted
- It stays; it must be deleted separately
- It is deleted automatically
Show answer

It stays; it must be deleted separately — docker rm -v only deletes anonymous volumes along with it.

Show the volume's details.

docker volume ____ pgdata

Show answer

docker volume inspect pgdata

Match.

volume ls

List
volume inspect

Details
volume rm

Delete
tar czf

Backup archive

Next lesson: Summary - Volumes

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