%files section of Singularity recipe non-intuitively copies files to wrong bind location - singularity-container

Question

I am working on CentOS 8 and am using Singularity 3.6.2. I have a Singularity recipe file :
BootStrap: yum
OSVersion: 8
MirrorURL: http://mirror.centos.org/centos-8/8/BaseOS/x86_64/os/
Include: yum
%files
/gpfs0/home1/group/user/path/to/some.rpm /tmp
%post
ls /tmp
echo "Hello from inside the container"
When I run :
$ sudo singularity build test.simg tmp
INFO: Starting build...
INFO: Skipping GPG Key Import
INFO: Adding owner write permission to build path: /tmp/rootfs-4db1e756-22a8-11eb-bb20-34800d2d90f0
INFO: Copying /gpfs0/home1/group/user/path/to/some.rpm to /tmp/rootfs-4db1e756-22a8-11eb-bb20-34800d2d90f0/tmp
INFO: Running post scriptlet
+ ls /tmp
qtsingleapp-RStudi-c679-6387e228-lockfile
rootfs-4db1e756-22a8-11eb-bb20-34800d2d90f0
rootfs-b10ad12c-229a-11eb-85a3-34800d2d90f0
+ echo 'Hello from inside the container'
Hello from inside the container
INFO: Creating SIF file...
According to the Singularity documentation
In the default configuration, the system default bind points are $HOME , /sys:/sys , /proc:/proc, /tmp:/tmp,
Question :
Why is the %files section putting my rpm in /tmp/rootfs-4db1e756-22a8-11eb-bb20-34800d2d90f0/tmp and not in /tmp? That seems to contradict the documentation. This is also different from the behavior observed with Singularity v2.5.1
Also, how would I access said file. The long 'hash-like' part of the path seems to change depending on the build?

Answer 1

I don't have an answer reconciling the documentation with where the %files section is actually putting the files, however I do have an answer for how to access the files copied. You need to use ${SINGULARITY_CONTAINER} in the %post section.
E.g.
$ cat Singularity
BootStrap: yum
OSVersion: 8
MirrorURL: http://mirror.centos.org/centos-8/8/BaseOS/x86_64/os/
Include: yum
%files
# Will need to use environmental variables to copy the code to
/gpfs0/home/group/user/path/to/some.rpm /tmp
%post
ls ${SINGULARITY_CONTAINER}/tmp
echo "Hello from inside the container"
When building yields :
$ sudo singularity build tmp.simg tmp
INFO: Starting build...
INFO: Skipping GPG Key Import
INFO: Adding owner write permission to build path: /tmp/rootfs-e2a3fbb4-242b-11eb-a267-34800d2d90f0
INFO: Copying /gpfs0/home/group/user/path/to/some.rpm to /tmp/rootfs-e2a3fbb4-242b-11eb-a267-34800d2d90f0/tmp
INFO: Running post scriptlet
+ ls /tmp/rootfs-e2a3fbb4-242b-11eb-a267-34800d2d90f0/tmp
some.rpm
+ echo 'Hello from inside the container'
Hello from inside the container
INFO: Creating SIF file...