The -v flag

Learn to mount volumes with the -v flag.

-v and --mount

There are two ways to write a volume mount. -v is short: source:target[:option]. --mount uses key=value form; it's longer but readable and reports errors more clearly:

docker run -d -v pgdata:/var/lib/postgresql/data postgres:16
docker run -d --mount type=volume,source=pgdata,target=/var/lib/postgresql/data postgres:16

Both give the same result.

Seeing the mounts

docker inspect shows a container's mounts with their types, sources and destinations:

$ docker inspect -f '{{range .Mounts}}{{.Type}} {{.Name}} -> {{.Destination}}{{"\n"}}{{end}}' db
volume pgdata -> /var/lib/postgresql/data

Exercise Mount with --mount

Start a container named cache from redis:7 in the background; mount the redisdata volume at /data with --mount.

Test yourself

In a bind mount, if the host folder doesn't exist, what is the difference between -v and --mount?
- -v silently creates the folder; --mount errors
- Both error
- Both create it
- --mount creates it; -v errors
Show answer

-v silently creates the folder; --mount errors — A mistyped path can silently become an empty folder with -v.

Give the target directory with --mount.

docker run -d --mount type=volume,source=pgdata,____=/var/lib/postgresql/data postgres:16

Show answer

docker run -d --mount type=volume,source=pgdata,target=/var/lib/postgresql/data postgres:16

Match.

-v

Short form
--mount

Key=value form
type=volume

Volume type
readonly

Read-only in --mount

Next lesson: Bind mounts

We Are Enhancing Your Experience

Cookie Preferences

Strictly Necessary Cookies

Analytical Cookies