CODEWITHSUNDEEP
docker
Luke101
Luke101

Reputation: 65288

How to specify source when creating a docker volume

According, to the docker documentation a volume can be created like this?

docker volume create myvol

is there a way to specify the source directory?

Upvotes: 1

Views: 1629

Answers (1)

bluescores
bluescores

Reputation: 4677

There are two kinds of Docker volumes: bind mount and named. A bind mount is done at runtime, and it's the one you're thinking about when you're talking about a source directory. It looks like this:

docker run -v /mydir:/app someimage

This would mount the /mydir directory on your host machine to /app in the running container.

A named volume doesn't have a source directory, it exists in the container space only. It's typically used to preserve data between container runs, because containers are ephemeral.

A common use case would be preserving the packages from an npm install, pip install or some other package manager for development. I may not want to re-download 100 packages every time I run my container. Instead, I could use a volume to persist them between runs:

docker run -v myvol:/app/node_modules someimage

The next time I start this container and mount myvol like this, myvol already has all of the installed packages from last time in /app/node_modules, so npm will simply scan over them quickly for updates and move along.

Also consider a named volume in the role of running a Dockerized database. Check this SO post, it has a very good answer: How to deal with persistent storage (e.g. databases) in Docker

Edit: bind mounts must start with a backslash for the host_src, otherwise docker run creates a named volume.

Upvotes: 3

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