Named volumes

Learn to create named volumes with docker volume create.

Named volume

A named volume can be created explicitly or is created automatically on first use. When an empty volume is mounted at a container directory, the contents of that directory in the image are copied into the volume:

docker volume create web-icerik
docker run -d --name web -v web-icerik:/usr/share/nginx/html nginx
# the volume now contains nginx's default index.html

Sharing and anonymous volumes

The same volume can be mounted into several containers; one writes, another reads. If only a container path is given in the form -v /path, an anonymous volume with a random name is created; these are hard to track, so named volumes are preferred:

docker run -d --name yazici -v loglar:/var/log/app api:1.0
docker run --rm -v loglar:/data:ro alpine tail /data/app.log   # :ro read-only
docker run -d -v /data redis       # anonymous volume: 8f3c1a…

Exercise A shared volume

Write three commands: create the loglar volume; start a container named api from api:1.0 in the background mounting this volume at /var/log/app; in an alpine container deleted when done, mount the volume read-only at /data and run ls /data.

Show example solution

docker volume create loglar
docker run -d --name api -v loglar:/var/log/app api:1.0
docker run --rm -v loglar:/data:ro alpine ls /data

Test yourself

What happens if the volume name given with -v doesn't exist?
- The container doesn't start
- Docker creates it automatically
- It errors
- It is interpreted as a bind mount
Show answer

Docker creates it automatically — If the name doesn't start with /, it counts as a named volume.

Mount the volume read-only.

docker run --rm -v loglar:/data____ alpine ls /data

Show answer

docker run --rm -v loglar:/data:ro alpine ls /data

Match.

docker volume create

Creates a volume
-v ad:/yol

Named volume
-v /yol

Anonymous volume
:ro

Read-only

Next lesson: The -v flag

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