mono isn't present on Ubuntu 24.04, but was on 22.04 and 20.04

[smkanadl]

Description

It is suggested to move to Ubuntu 24.04. In my case I cannot move as I need mono installed on the agent.

According to this comment the removal may be fully intentional. In such a case documentation would be very helpful.

Platforms affected

• Azure DevOps
• GitHub Actions - Standard Runners
• GitHub Actions - Larger Runners

Runner images affected

• Ubuntu 20.04
• Ubuntu 22.04
• Ubuntu 24.04
• macOS 13
• macOS 13 Arm64
• macOS 14
• macOS 14 Arm64
• macOS 15
• macOS 15 Arm64
• Windows Server 2019
• Windows Server 2022
• Windows Server 2025

Image version and build link

Ubuntu 20.04: https://dev.azure.com/smkanadl/MissingMono/_build/results?buildId=54614&view=logs&j=19e123c8-1d38-5919-a21c-51ca211d3047&t=c7dd368d-7fd7-507a-3c9d-b7eacfac1b8d
Ubuntu 22.04: https://dev.azure.com/smkanadl/MissingMono/_build/results?buildId=54614&view=logs&j=0cb671f7-629c-572a-49d6-d57c236578ac&t=a33fe29a-42a6-5efa-425f-0b98b5c13dac
Ubuntu 24.04: https://dev.azure.com/smkanadl/MissingMono/_build/results?buildId=54614&view=logs&j=b104dce4-27c6-5299-f400-f77b321f7309&t=098fd864-c404-56ce-32c3-a874bcd418ba

Is it regression?

Yes

Expected behavior

Have mono installed as it is still a valuable tool.

Actual behavior

mono is not available

Repro steps

Use Ubuntu 24.04 and try dotnet test on a solution with tests being build with net48.

[vidyasagarnimmagaddi]

Hi @smkanadl ,Thank you for bringing this issue to our attention. We will look into this issue and will update you after investigating.


[Prabhatkumar59]

Hi @smkanadl - In meantime, we request you to provide any workflow and repro steps link as well to debug into this furthermore.
Thanks!

[smkanadl]

@Prabhatkumar59 the actual code is confidential work stuff, but I setup a small example repo to demonstrate the issue compared to Ubuntu 20.04 and Ubuntu 22.04 and added links to the report.

Here is the link to the overall build.

[Prabhatkumar59]

Hi @smkanadl - Thanks for the inputs, we will look into this and will update you.

[manfred-brands]

We noticed the same when ubuntu-latest was upgraded to ubuntu-22.04
Our workflow is C# libraries targeting .net framework and net8.0.
Previously dotnet test worked fine, now it complains about mono not found.
Manually installing mono works but significantly adds time to the run.

Mono is listed in Ubuntu-22.04
but not in Ubuntu-24.04

[zlh04]

This is also the case for NuGet and Terraform as stated here in Microsoft Documentation