Update/Add .NET 9 SDK to Ubuntu 24.04

[nimro]

Tool name

.NET SDK 9.x

Tool license

MIT

Add or update?

• Add
• Update

Desired version

9.x (latest with v9)

Approximate size

No response

Brief description of tool

The .NET SDK, for .NET 9. This is already installed in the Ubuntu 22.04 image: https://github.com/actions/runner-images/blob/ubuntu24/20250330.1/images/ubuntu/Ubuntu2204-Readme.md#net-tools but is missing from 24.04.

URL for tool's homepage

No response

Provide a basic test case to validate the tool's functionality.

Platforms where you need the tool

• Azure DevOps
• GitHub Actions

Runner images where you need the tool

• 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

Can this tool be installed during the build?

Tool installation time in runtime

No response

Are you willing to submit a PR?

No response

[nimro]

Related to #11965, I also noticed this due to the switch of ubuntu-latest to in Azure Pipelines

[vidyasagarnimmagaddi]

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

[dominik-weber]

Please look into this issue. We're using ubuntu-latest by default for all our projects, this change means that most of our pipelines broke overnight and need manual fixing :/

For anyone searching for an interim solution, add this to your yaml files:

pool:
  vmImage: ubuntu-22.04 # ubuntu-latest currently does not ship with .NET 9 SDK

[hemanthmanga]

Hi All,
We have added the .NET 9 version to both Ubuntu 20 and Ubuntu 22. Kindly check the change. However, for Ubuntu 24, .NET 9 is not yet available in the package manager as it is currently not supported in the built-in Ubuntu feed. If needed, you can install it manually use backports, configure it with setup-dotnet or switch to ubuntu-22.04 instead of ubuntu-latest. For more information, please read the complete documentation. We are closing this issue, Thank you.

[dominik-weber]

Hi @hemanthmanga, thanks for the update!

Would you consider switching ubuntu-latest back to 22 until .NET 9 becomes available in the 24 image? I wouldn't consider the issue resolved until this is included - the change still is a regression for everyone using ubuntu-latest (and relying on .NET 9) in their pipelines.

[nimro]

Incredible. Microsoft's own image for its own CICD platforms is unable to run Microsoft's premier development toolchain because... what, it's too much effort to set up the backports PPA yourselves? You have to wait for a third party to do it for you (via the apt mainline feed)?

Marking this issue as "completed" is total fiction.