.NET 8 Preview 1 Release

[mthalman]

.NET 8 Preview 1 Release

Containers images for .NET 8 Preview 1 have been published.

Preview 1 includes the following improvements in how container images can be used for .NET applications:

Update default Linux distro to Debian 12

Container images now use Debian 12 (Bookworm) the LTS (Long-term support) version that shipped earlier this year. In order to give our community plenty of time for the transition, we try to adopt it with Preview 1.

Tagging change

.NET 8 preview container images will use the 8.0-preview tag (not 8.0) and transition to 8.0 with the Release Candidate releases. The goal of this approach is to more clearly describe preview releases as such. This change was made based on a community request.

Run container with a non-root user

Though container base images are almost always configured to run with the root user – a setting which tends to be kept in production – it is not always the best approach. It is a pain to configure each application to have a different user, however, and container images do not come with a non-root user that is appropriate for container workloads.

.NET 8 offers a better way. Starting with Preview 1, all container images we publish will be non-root capable. Here is an example of the single line used to run a container as non-root for Dockerfiles:

USER app

In addition, you can now launch container images with -u app. The default port has changed from port 80 to 8080. This is a breaking change that was necessary in order to enable the non-root scenario, since port 80 is a privileged port.

Ubuntu Chiseled images

We are publishing Ubuntu Chiseled images with .NET 8. This type of image is for developers that want the benefit of appliance-style computing, even more so than you get with regular containers. We expect that Ubuntu chiseled images will be supported in production by both Canonical and Microsoft by the time .NET 8 ships.

We plan to ship to dotnet/monitor images exclusively as Ubuntu Chiseled, starting with .NET 8. That’s notable because the monitor images are the one production app image we publish.

Chiseled images have a lot of benefits:

• Ultra-small images (reduced size and attack surface)
• No package manager (avoids a whole class of attacks)
• No shell (avoids a whole class of attacks)
• Non-root (avoids a whole class of attacks)

You can see the pattern for producing chiseled images, with our aspnetapp sample. It only requires a one-line change.

Chiseled images are currently published to our nightly repos, for .NET 6 and .NET 7 versions.

Summary

We look forward to hearing your feedback on these changes. Read about all the other .NET 8 Preview 1 changes in the .NET blog post.