What is the right way to add data to an existing named volume in Docker?

Question

I was using Docker in the old way, with a volume container:

docker run -d --name jenkins-data jenkins:tag echo \"data-only container for Jenkins\"


        

Answer 1

You can certainly copy data directly into /var/lib/docker/volumes/my-jenkins-volume/_data, but by doing this you are:

• Relying on physical access to the docker host. This technique won't work if you're interacting with a remote docker api.

• Relying on a particular aspect of the volume implementation would could change in the future, breaking any processes you have that rely on it.

I think you are better off relying on things you can accomplish using the docker api, via the command line client. The easiest solution is probably just to use a helper container, something like:

docker run -v my-jenkins-volume:/data --name helper busybox true
docker cp . helper:/data
docker rm helper

Answer 2

Here are steps for copying contents of ~/data to docker volume named my-vol

Step 1. Attach the volume to a "temporary" container. For that run in terminal this command :

docker run --rm -it --name alpine --mount type=volume,source=my-vol,target=/data alpine

Step 2. Copy contents of ~/data into my-vol . For that run this commands in new terminal window :

cd ~/data docker cp . alpine:/data

This will copy contents of ~/data into my-vol volume. After copy exit the temporary container.

Answer 3

You can reduce the accepted answer to one line using, e.g.

docker run --rm -v `pwd`:/src -v my-jenkins-volume:/data busybox cp -r /src /data

Answer 4

You don't need to start some container to add data to already existing named volume, just create a container and copy data there:

docker container create --name temp -v my-jenkins-volume:/data busybox
docker cp . temp:/data
docker rm temp