Run command podman -v /source_volume:/container_dir and it throw an error Error: statfs /source_volume: no such file or directory

[geekerNo1]

Is this a BUG REPORT or FEATURE REQUEST? (leave only one on its own line)

/kind feature

Description
Accodring to doc https://docs.podman.io/en/latest/markdown/podman-run.1.html. Podman -v will mount the source volume to container dir. If no such named volume exists, podman will create one.
But when I mount an volume which is not exists, it will throw an error, "Error: statfs /volume_dir: no such file or directory"

Steps to reproduce the issue:

1. podman run -it --volume /tmp/abcd:/tmp/test --name "test" <container_name>
   Error: statfs /tmp/abcd: no such file or directory
2. podman run -it -v /tmp/abcd:/tmp/test --name "test" <container_name>
   Error: statfs /tmp/abcd: no such file or directory

Output of podman version:

podman version 4.0.2

[flouthoc]

Hi @geekerNo1 Thanks for creating the issue.

In following command --volume /tmp/abcd:/tmp/test the volume source does not looks like name to volume but instead looks like a path on host where user is making an attempt towards creating bind mount inside container. The documentation states true if you attempt to mount a podman volume so something like --volume my-vol:/tmp/test should automatically create podman volume if it does not exists and you can further verify using podman volume ls.

I am not sure if podman should attempt to create a named volume where name actually looks like a path on host since this could lead to scenarios where podman run will confuse it user is requesting a path on host or a named volume which looks like path.

Tagging @containers/podman-maintainers for input here.

[geekerNo1]

Hi @flouthoc Thanks for you reply.

/tmp/abcd is a path on host, not a volume. I confuse those two. Sorry about that mistake.

I attempt to use podman instead of docker on rhel8. I want to use command podman -v /tmp/abcd:/tmp/test to instead of docker command docker -v /tmp/abcd:/tmp:test.
If the path /tmp/test is not exists on host

1. run command podman -v /tmp/abcd:/tmp/test, it will throw an error Error: statfs /tmp/abcd: no such file or directory.
2. run command docker -v /tmp/abcd:/tmp/abcd, it will automatically creates the dir on host.

So I guess that this is a difference between docker and podman, right?
Looking forward to your reply

[flouthoc]

@geekerNo1 Thanks for making it clear. I can also confirm docker creates path on host if it does not exists and i think in such case podman should do the same.

[giuseppe]

I think the Podman behavior is saner. It helps to find out typos more easily. e.g. something like mkdir /tmp/foo; podman run -v /tmp/fo:/foo ... would not be easily detected if Podman would automatically create the directory.

[Luap99]

This was discussed before and we (Podman maintainers) think this is a bug. What if you have a typo now podman creates a new empty directory and does not use the one you intended or what if you want to bind mount a file and the file simply does not exists?

[Luap99]

Also see #10471 and #6234
I know that there are more issues with more discussion about this but I cannot find them right now.

Anyway this is something we decided not to do.

[vrothberg]

This was discussed before and we (Podman maintainers) think this is a bug. What if you have a typo now podman creates a new empty directory and does not use the one you intended or what if you want to bind mount a file and the file simply does not exists?

All of them are closed and the docs seem to be wrong. I suggest reopening and reflecting the reasoning in the docs.

[Luap99]

Which docs are you talking about? I see this:

From https://docs.podman.io/en/latest/markdown/podman-run.1.html#volume-v-source-volume-host-dir-container-dir-options

If the source does not exist, Podman will return an error. Users must pre-create the source files or directo‐
ries.

[flouthoc]

This was discussed before and we (Podman maintainers) think this is a bug.

Ah i see but I don't think this is bug at docker end but more like expected behavior on the docker side. The docs here mention this behavior https://docs.docker.com/engine/reference/commandline/run/#mount-volume--v---read-only

"When the host directory of a bind-mounted volume doesn’t exist, Docker will automatically create this directory on the host for you"

But reasoning here makes sense to me: #6234 (comment)

[vrothberg]

Which docs are you talking about? I see this:

From https://docs.podman.io/en/latest/markdown/podman-run.1.html#volume-v-source-volume-host-dir-container-dir-options

If the source does not exist, Podman will return an error. Users must pre-create the source files or directo‐
ries.

See the issue description. The doc also states "If no such named volume exists, Podman will create one". The two conflict and if users look for that information they will very likely stop reading at some point.

[rhatdan]

Podman is working correctly. We should NOT create the source directory. Docker might do this but I see it as a bug.
Would you expect mount -o bind /tmp/abcd /mnt to create /tmp/abcd?

If the docs say that we create the source directory then the docs need to be fixed.
If Docker has bad design or what we feel is clearly a bug easily remedied by the user, then we should not implement the bug for compatibility purposes.

[vrothberg]

Reopening as the docs should be less confusing.

[geekerNo1]

Thanks all helps! Now I got it. Close the issue.

[domdomegg]

(duplicate of #6234)