Adding non-root user in jammy issues results in image size increase

[lbussell]

See #4587. I investigated the difference between the two images:

• mcr.microsoft.com/dotnet/nightly/runtime-deps@sha256:24cc8445fa87fb3771d40628f6745b3988f425dcd3d6fb80a2384305ae7c536e (new)
• mcr.microsoft.com/dotnet/nightly/runtime-deps@sha256:1dd42bff18ccd210bea44f481ee3b49db9cea509e7b7ff2a2e2b3e5aff3a1ac3 (old)

The culprit here is the /var/log/lastlog file. It has increased in size from 30kb to 19mb. /var/log/faillog has also increased in size from 3.3kb to 2.1mb. This requires some more investigation.

[mthalman]

In general, we should probably be cleaning up log files, especially those of this size.

[lbussell]

So this actually happens because of #4476. /var/lib/lastlog stores user login data indexed by UID. So when we increased the UID we inadvertently made this file really big. The solution is to run adduser with the -l option which omits these log files. PR incoming for that.

[lbussell]

This particular /var/lib/lastlog issue is fixed with #4593