nixos-generate-config: observe device label if present

[acobster]

Partially fixes #27789 by using matching devices found in /dev/disk/by-label/* before using any found in /dev/disk/by-uuid/*.

Wil T's install tutorial explains the motivation: https://www.youtube.com/watch?v=axOxLJ4BWmY&t=1295s

Description of changes

This doesn't change any packages; only newly generated hardware configurations are affected.

This does NOT fix #27789 as originally reported (I was not able to repro that myself), but does address this comment.

At some point the automatic detection of device labels broke and device UUIDs began taking precedent over labels. This makes setting up a new computer a more manual and error-prone process than it needs to be.

With this change, I can instead use the devices generated as-is in hardware-configuration.nix on reinstall.

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandboxing enabled in nix.conf? (See Nix manual)
  • sandbox = relaxed
  • sandbox = true
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 24.11 Release Notes (or backporting 23.11 and 24.05 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
• Fits CONTRIBUTING.md.

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[roberth]

I'm not all that knowledgeable about this topic, but I guess I can review the process.

• Could you document the rationale for these priorities in a comment?

• This should - presumably - break a test case. Let's see:

@ofborg build nixos-install-tools.tests

[Aleksanaa]

Yes this should be preferred. Further change would be also using by-partuuid in favor of by-uuid, but that's not tested

[geovex]

by-partlabel will also be nice to have (very handy for exotic configs)

[roberth]

This doesn't change any packages; only newly generated hardware configurations are affected.

Automated installations may still be affected by this, so this is worth adding to the release notes. Could you do that?

[sigprof]

The choice between various device ID types may be complicated:

• User-specified filesystem or partition labels have some chance of collisions if a “foreign” storage device originally from another machine is connected during boot for some reason (e.g., for data recovery purposes). UUIDs are safer in that respect.
  • One option to avoid some collisions is to include the hostname in the label; however, some filesystems have severe restrictions on the label size which may interfere with that (e.g., XFS supports at most 12 characters).
• However, if LVM is used, filesystem UUIDs should not be used to identify devices, because LVM supports snapshots, which would appear to have the same UUIDs as the origin filesystems. Currently nixos-generate-config ignores this issue and uses /dev/disk/by-uuid/* in preference to /dev/mapper/*.
  • Swapping from /dev/disk/by-uuid/* to /dev/mapper/* could potentially introduce the same increased collision chance as using filesystem or partition labels. However, LVM volume group names often include the hostname, which partially mitigates the problem, and LVM would also detect duplicate volume group names with different UUIDs and refuse to work until the collision is resolved.
  • Also the /dev/mapper/* namespace is not exclusively used by LVM, therefore some extra checks might be needed.

[acobster]

@roberth done.

[roberth]

@ofborg build nixos-install-tools.tests