Apptainer: Application Containers for Linux

Apptainer and singularity ce are quite common in HPC. While both implementations fork the old singularity project, they are not really identical.

We use singularity in the HPCs (like Leonardo, LUMI, Fugaku, NeSI NZ, Levante) but some devs and researchers have apptainer installed locally.

We found a timezone bug a few days ago in our Python code (matplotlib,xarray,etc.), but that didn't happen with apptainer.

As the code bases are still a bit similar, I could confirm apptainer fixed it but singularity ce was still affected by the bug -- singularity replaces the UTC timezone file by the user's timezone, Helsinki EEST in our case in LUMI HPC.

https://github.com/sylabs/singularity/issues/3686

Luckily they’re still compatible with each others containers. Can use Apptainer to build the container then run it on Singularity and vice-versa.

> Apptainer and singularity ce are quite common in HPC. While both implementations fork the old singularity project, they are not really identical.

Apptainer is not a fork of the old Singularity project: Apptainer is the original project, but the community voted to change its name. It also came under the umbrella of the Linux Foundation:

* https://apptainer.org/news/community-announcement-20211130/

Sylabs (where the original Singularity author first worked) was the one that forked off the original project.

Oh, that's correct. Thanks!

Yeah, we haven't found any issues so far besides this one with time zone. Other than that, we've been able to run the same containers with both.