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ยท 2 min read
German P. Barletta

This is probably the last of a series of blog posts on singularity.

We know how to build a simple container with CUDA support and we know how to build a more complex one that also has conda support. We'll now sign our container (locuaz.sif) and upload it for others to download. Honestly, this is the easiest part of all and I'm only writing it down for future reference.

Intro (digression)

Before starting, we have to clarify something: Singularity is no more. In a weird turn of events, a company forked it and called it to Singularity CE, while the original project had to rename itself to Apptainer and is now under the umbrella of the Linux Software Foundation, which I guess protects it from stuff like this happening again, but, honestly, I have no idea.

As of now, an HPC cluster can be expected to have a singularity module but I haven't found one with apptainer built-in, so we'll stay with sylabs, at least for now.

The sylabs way

Creating a key to sign containers

In order to sign something you need a signature and Singularity's docs are straightforward in this regard, just do what they say

Creating a sylabs token to verify containers

You'll also want the ability to verify a signature. Creating an account on sylabs allows you to verify containers from others and upload yours. Sadly, they don't let you create an account, but force you to integrate their credentials with github, or gmail, etc.

Signing and uploading with sylabs

After all of that, it's just:

singularity sign locuaz.sif

and to verify the signature, users will do:

$ singularity verify locuaz.sif 
INFO: Verifying image with PGP key material
[LOCAL] Signing entity: Patricio Barletta <[email protected]>
Objects verified:
1 |1 |NONE |Def.FILE
2 |1 |NONE |JSON.Generic
3 |1 |NONE |JSON.Generic
4 |1 |NONE |FS
INFO: Verified signature(s) from image 'locuaz.sif'

Finally, push it to your sylabs library. In my case, that looks like:

singularity push locuaz.sif library://pgbarletta/remote-builds/locuaz-0.5.3

Sylabs will give you 11Gb of storage for free, so you'll be good for a couple of images. It'd be fun to try and see if an Apptainer image gets accepted, my guess is a big resounding ....