buildah mount locations not visible to the host

[gireeshpunathil]

Description

Steps to reproduce the issue:

1. Get into quay.io/builda container, with a mount:
   docker run --privileged -it -v /a:/b -v containers:/var/lib/containers quay.io/buildah/stable /bin/sh

2. Create something under the mount
   echo hello > /b/foo.txt

3. Create a container from scratch, with the mount forwarding to the child
   buildah from --name cont -v /b:/c scratch

4. Get the mount point of the chile
   mount=``buildah mount cont`

5. Check the content of the mount point:
   ls -lrt $mount/
   Describe the results you received:

I got total 0

Describe the results you expected:

I expected:
-rw-r--r-- 1 root root 6 Aug 22 13:56 foo.txt or similar
Output of rpm -q buildah or apt list buildah:

I have tried several mount options such as :shared etc. but did not succeed.

If I run buildah run on the container and get in, I can see the mount points properly - which indicates the mount, and its access permissions, visibility and share-ability are all good.

buildah-1.9.2-2.fc30.x86_64

Output of buildah version:

Version:         1.9.2
Go Version:      go1.12.7
Image Spec:      1.0.1
Runtime Spec:    1.0.1-dev
CNI Spec:        0.4.0
libcni Version:  
Git Commit:      
Built:           Thu Jan  1 00:00:00 1970
OS/Arch:         linux/amd64

Output of podman version if reporting a podman build issue:

(paste your output here)

Output of cat /etc/*release:

Fedora release 30 (Thirty)

Output of uname -a:

Linux a9cebbb7863d 4.9.184-linuxkit #1 SMP Tue Jul 2 22:58:16 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux

Output of cat /etc/containers/storage.conf:

driver = "overlay"
runroot = "/var/run/containers/storage"
graphroot = "/var/lib/containers/storage"

[storage.options]
additionalimagestores = [
"/var/lib/shared",
]
size = ""
mount_program = "/usr/bin/fuse-overlayfs"
override_kernel_check = "true"
mountopt = "nodev,metacopy=on"
[storage.options.thinpool]
ostree_repo = ""
skip_mount_home = "false"

Thanks in advance!

[rhatdan]

This definitely looks like a bug. @TomSweeneyRedHat PTAL

[rhatdan]

So the volumes are only getting mounted during a RUN or Build. The issue is we rely on the OCI runtime to actually create the content and mount the bind mounts.

[TomSweeneyRedHat]

@rhatdan is there something we can do with this? I'm not sure this is unexpected for the mount command as it's used in the example.

[rhatdan]

Yes I think we need to close this since we really can not fix this is a reasonable way other then to tell user to run the container

As soon as you do a
buildah run $CTR echo hello
The mount point point will change.

[rhatdan]

We could document this though.

[gireeshpunathil]

I will close this out in favor of #1821 , as I guess we are talking about the same thing or the underlying issue is one and the same, and #1821 has more context.

Thanks!