Missing sub-folders and files from the mount point

General Discussions
1

I am trying to persist the entire configuration folder of an application on the host system but I noticed that only partial content is written. I cannot locate some of the files under the /var/lib/docker/volumes/ folder. Following is the command I run:

# docker volume create etcsalt
# docker run --name salt --hostname salt -p 4505-4506:4505-4506 -p 8000:8000 -e SALT_SHARED_SECRET=mysecretpassword --ulimit nofile=90000:90000 --mount source=etcsalt,target=/etc/salt -d saltstack/salt:3004.2

I think the following link shows the Dockerfile for the project:

Once the container starts, I check the content of the volume:

root@test:/var/lib/docker/volumes/etcsalt/_data# ls
master.d  minion.d  pki  proxy.d

master.d folder has a couple of files I am looking. The rest of the folders are blank. This is not the case when I check the same folders inside the container.

Can someone provide me some direction here.

Thanks,

2

I just noticed that when I create a different mount point for each subfolder and run the docker with multiple mount points, I see the files I am looking. I can stop and remove the active docker container and start a new one and everything works as expected.

docker volume create etcsalt-master.d
docker volume create etcsalt-minion.d
docker volume create etcsalt-pki
docker volume create etcsalt-proxy.d

docker run --name salt --hostname salt -p 4505-4506:4505-4506 -p 8000:8000 -e SALT_SHARED_SECRET=mysecretpassword --ulimit nofile=90000:90000 \
--mount source=etcsalt-master.d,target=/etc/salt/master.d \
--mount source=etcsalt-minion.d,target=/etc/salt/minion.d \
--mount source=etcsalt-pki,target=/etc/salt/pki \
--mount source=etcsalt-proxy.d,target=/etc/salt/proxy.d \
-d saltstack/salt:3004.2

What could be the reason for this kind of behavior?

3

If you look into the Dockerfile you linked, you cans ee this line:

VOLUME /etc/salt/pki/

You mounted /etc/salt and I guess the volume defined in the Dockerfile was mounted over it. Since you havenā€™t defined any volume with the same destination path (the path after the VOLUME instruction in Dockerfile) Docker created an anonymous volume ( its name is a hash ) so the content of the ā€œpkiā€ folder was saved there.

I donā€™t know about the rest of the folders. I guess those folders were empty even when you mounted multiple volumes.

This is why I donā€™t like to use the VOLUME instruction in the Dockerfile as you canā€™t undo it.

1 Like
4

Thank you. I donā€™t want to mess with the official dockerfile of the project. I think I will work around it and define more specific mount points.