Microsoft Slurm apt repo does not reference a "signed-by" key which seems to break CycleCloud VM initialisation with the latest Ubuntu release?

Hi,

I think this is a CycleCloud team issue (as CycleCloud installs the slurm packages ontop of the image during VM initialisation), rather than an AzHPC image team issue, or an Ubuntu issue, but feel free to correct me, as I may well be wrong...

Using the latest AzHPC Ubuntu 22.04 Marketplace image works fine, but if I "roll-my-own" image from the latest Ubuntu 22.04 LTS Marketplace image and apply the AzHPC repo build scripts to it (so I have all the latest security fixes), CycleCloud fails to initialise the Scheduler node, giving this error in the UI:

> STDOUT:
> (...64 lines trimmed...)
> W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: https://packages.microsoft.com/repos/amlfs-jammy jammy InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY EB3E94ADBE1229CF
> W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: https://packages.microsoft.com/repos/slurm-ubuntu-jammy insiders InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY EB3E94ADBE1229CF
> W: Failed to fetch https://packages.microsoft.com/repos/amlfs-jammy/dists/jammy/InRelease The following signatures couldn't be verified because the public key is not available: NO_PUBKEY EB3E94ADBE1229CF
> W: Failed to fetch https://packages.microsoft.com/repos/slurm-ubuntu-jammy/dists/insiders/InRelease The following signatures couldn't be verified because the public key is not available: NO_PUBKEY EB3E94ADBE1229CF
> W: Some index files failed to download. They have been ignored, or old ones used instead.
> + apt install -y python3.11 python3.11-venv python3.11-dev
>
> WARNING: apt does not have a stable CLI interface. Use with caution in scripts.
>
> E: dpkg was interrupted, you must manually run 'dpkg --configure -a' to correct the problem.What is the issue?

It looks to me (I may be wrong?) as if the latest version released of Ubuntu has tightened up on not allowing repo's that don't use the new "signed-by" key mechanism which they have been switching to for several years now. But, this is a guess, am no expert, I may be wrong.

This is the Slurm repo config file that CycleCloud installs (which gives the key error above with apt update):

root@test-scheduler:/etc/apt/sources.list.d# cat slurm.list
deb [arch=amd64] https://packages.microsoft.com/repos/slurm-ubuntu-jammy/ stable main

if I change the slurm.list file to this:
deb [arch=amd64 signed-by=/usr/share/keyrings/microsoft-prod.gpg] https://packages.microsoft.com/repos/slurm-ubuntu-jammy/ stable main

Then apt update works fine and the scheduler node goes green in the CycleCloud UI.

So - I think the Slurm repo config or CycleCloud initialisation steps need fixing so that the /etc/apt/sources.list.d/slurm.list file is of a format that the very latest Ubuntu 22.04 release will allow:

deb [arch=amd64 signed-by=/usr/share/keyrings/microsoft-prod.gpg] https://packages.microsoft.com/repos/slurm-ubuntu-jammy/ stable main

Note - I saw this issue with with the latest Marketplace image:

grma@emospot-scheduler:~$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 22.04.5 LTS
Release: 22.04
Codename: jammy

grma@emospot-scheduler:~$ uname -a
Linux emospot-scheduler 5.15.0-1111-azure #120-Ubuntu SMP Wed Apr 15 15:09:04 UTC 2026 x86_64 x86_64 x86_64 GNU/Linux

Start with the generated /etc/apt/sources.list.d/slurm.list entry and trace the CycleCloud initialization or repository configuration that creates it. Reproduce apt update on Ubuntu 22.04.5, then verify the Microsoft key is referenced with signed-by and that scheduler initialization completes successfully.

Written by the indexing model from the issue text.