Move docker bind-mount to volume

Question

Actually, I run my containers like this, for example :

docker run -v /nexus-data:/nexus-data sonatype/nexus3
              ^

After reading the documentation, I discover volumes that are completely managed by docker. For some reasons, I want to change the way to run my containers, to do something like this :

docker run -v nexus-data:/nexus-data sonatype/nexus3
              ^

I want to transfer my existing bind-mount to volumes.

But I don't want to lose the data into /nexus-data folder, is there a possibility to transfer this folder, to the new volume, whitout restart everything ? Because I've also Jenkins and Sonar containers for example, I just want to change the way to have persistent data. The is a proper way to do this ?

Answer 1

You can try out following steps so that you will not loose your current nexus-data.

#>docker run -v nexus-data:/nexus-data sonatype/nexus3
#>docker copy /nexus-data/. <container-name-or-id>:/nexus-data/
#>docker stop <container-name-or-id>
#>docker start <container-name-or-id>

docker copy will copy data from your host-machine's /nexus-data folder to container's FS /nexus-data folder which is your mounted volume.

Let me know if you face any issue while performing following steps.

Answer 2

Here's another way to do this, that I just used successfully with a Heimdall container. It's outlined in the documentation for the sonatype/nexus3 image:

1. Stop the running container (e.g. named nexus3)
2. Create a docker volume called nexus-data, creating it with the following command: docker volume create nexus-data)
3. By default, Docker will store the volume's content at /var/lib/docker/volumes/nexus-data/_data/
4. Simply copy the directory where you previously had been using a bind mount to the aforementioned volume directory (you'll need super user privileges to do this, or for the user to be part of the docker group): cp -R /path/to/nexus-data/* /var/lib/docker/volumes/nexus-data/_data/
5. Restart the nexus3 container with $ docker run -v nexus-data:/nexus-data sonatype/nexus3 --name=nexus3
6. Your container will be back up and running, with the files persisted in the directory /path/to/nexus-data/ now mirrored in the docker volume. Check if functionality is the same, of course, and if so, you can delete the /path/to/nexus-data/ directory

Q.E.D.