Files copied with %file are not seen by %post under Windows + WSL2 + Ubuntu

[sapetnioc]

I am trying to use Singularity (3.6.1+21-g0441c656a-dirty) under Windows with Ubuntu 18.04 and a fresh update providing WSL2 (a true Linux kernel in Windows 10). I was pleased to see that using images worked for me. (this was not the case with WSL1). But I got an error for image creation if I try to use files copied by %file in a %post section. I did the following :

touch /home/me/test.sh
sudo singularity build /tmp/test.sif /home/me/recipe

With the following recipe file :

Bootstrap: docker
From: ubuntu:18.04

%files
    /home/me/test.sh /tmp/test.sh

%post
    ls $SINGULARITY_CONTAINER/tmp
    chmod +x /tmp/*.sh

This produces the following output :

...
INFO:    Copying /home/me/test.sh to /tmp/rootfs-0530dbd9-e236-11ea-99e0-5e822267d58a/tmp/test.sh
INFO:    Running post scriptlet
+ ls /tmp/rootfs-0530dbd9-e236-11ea-99e0-5e822267d58a/tmp
test.sh
+ chmod +x /tmp/*.sh
chmod: cannot access '/tmp/*.sh': No such file or directory
FATAL:   While performing build: while running engine: exit status 1

test.sh is copied but is not accessible in /tmp from the %post script. It is located in /tmp/rootfs-<uuid>/tmp. This error is not present under a true Linux workstation.

[vsoch]

hey @sapetnioc you would want to post issues to https://github.com/hpcng/singularity/issues - this is the web documentation for container tools (Singularity Hub, Registry, etc.). I can't transfer the issue because it's a different org, otherwise I'd do that for you. But one thing to try - since you are listing in $SINGULARITY_CONTAINER/tmp why not just chmod there? It does seem like a bug though, I'd report it.

[sapetnioc]

I will post the issue where it is supposed to go. Sorry.

Yes I can find a workaround but I noticed that in Linux, there is no SINGULARITY_CONTAINER variable but SINGULARITY_ROOTFS instead. But I realize that I do not have the same Singularity version on Linux (3.5.3). I should have checked that before saying it works on Linux.

[vsoch]

If I remember correctly, in %post you shouldn't need to use SINGULARITY_CONTAINER or SINGULARITY_ROOTFS - it's only in setup. But one other detail - during build your container will bind your /tmp, so if you copy something to there isn't probably not going to persist. Maybe try somewhere else instead? This seems to work:

Bootstrap: docker
From: busybox

%files
    test.sh /opt/test.sh

%post
    ls /opt
    chmod +x /opt/*.sh

$ singularity shell container.sif 
Singularity> ls /opt/
test.sh

Most users won't use --containall to even if you had content in tmp, they probably wouldn't see it. It's safer not to use these automatically mounted folders.

[sapetnioc]

I may have been lazy but I did not find information about /tmp in the doc. I only searched tmp and temp in the recipe file page. This may be a good idea to add a warning there.

Thank you for your answers, this was very helpful.