Container archive produces tar - not gzip tar?!

[sebader]

I'm trying the new option to produce the docker image as a compressed archive (https://github.com/dotnet/sdk-container-builds/issues/283). In general this seems to work, however, the file seems to be a tar file, not a tar.gz

When trying to use gunzip (on Linux or MacOS) it fails with:

gunzip sdk-container-demo.tar.gz
gunzip: sdk-container-demo.tar.gz: not in gzip format

When trying to open the file on MacOS with 7z (7z x sdk-container-demo.tar.gz), it succeeds, but just because 7z just falls back to untar-only.

Extracting archive: sdk-container-demo.tar.gz
WARNING:
sdk-container-demo.tar.gz
Can not open the file as [gzip] archive
The file is open as [tar] archive

Produced the file with:

dotnet publish ./src/myproject/myproject.csproj -p ContainerArchiveOutputPath=./images/sdk-container-demo.tar.gz -p PublishProfile=DefaultContainer

dotnet --version 8.0.100-rc.2.23502.2

cc @Danielku15

[Danielku15]

Currently this behavior is intended and aligned with what docker save does. docker load would support also compressed archives. I was working and planned to contribute further functionalities around this feature but they didn't make it into net8.0 and seem to be a bit on hold due to the .net team entering the release phase of net8.0. With this functionality here there would be a new setting to control what kind of output archive is written and tar.gz could be a second extension. https://github.com/dotnet/sdk/pull/35204

If the other extensions make it to the SDK I would guess also DockerTarGz could easily be an additional format that can be supported.

Of course there might be always the possibility to gzip the tar manually if this is required for your workflow.

It might be a wrong expectation that the archive format and compression is auto-detected by the file extension, this is not the case.

[sebader]

I'm totally fine if the behavior is right now that it produces a tar file instead of a gzip. But then the docs must not refer everywhere to it with .tar.gz. That is just wrong. It raises false expectations and creates confusion (and failed CI pipelines in my case...)

[Danielku15]

That's indeed wrong. The feature I made added "tar" writing aligned with docker save, not yet "tar.gz" which is mentioned at various places 😱

@baronfel Please let me know if I should prepare a code change around this feature (e.g. to auto-detect tar vs tar.gz or whether to always write tar.gz)

[baronfel]

Excellent catch folks - I think it's best to try and fix doc mentions of tar.gz in the docs first, then add explicit support for toggling compression as a separate feature.

Do you have some links to where you've seen the incorrect docs?

[Danielku15]

I only saw it in the announcement and the related issue:

• https://devblogs.microsoft.com/dotnet/announcing-dotnet-8-rc2/
• https://github.com/dotnet/sdk-container-builds/issues/283

This page does not yet mention the new options:

• https://learn.microsoft.com/en-us/dotnet/core/docker/publish-as-container?pivots=dotnet-8-0
• https://github.com/dotnet/docs/blob/main/docs/core/docker/publish-as-container.md

The documentation work item you added was: https://github.com/dotnet/sdk-container-builds/issues/497

[sebader]

Yeah I came across it in the announcment blog - which links to the issue #283 as well as the PR, both say "tar.gz" https://github.com/dotnet/sdk/pull/35151

[sebader]

Excellent catch folks - I think it's best to try and fix doc mentions of tar.gz in the docs first, then add explicit support for toggling compression as a separate feature.

Do you have some links to where you've seen the incorrect docs?

just a ping on this @baronfel The links don't seem to have been updated.