How can I install specifically util-linux from unstable

Help
2

Several things here:

  1. Changing util-linux system-wide is very non-trivial, because too many things depend on it. You can do it in an overlay, but you will end up re-compiling half of nixpkgs. Instead of putting it in an overlay, you can just put it in systemPackages, but then the important things like systemd won’t use it.

  2. nixos-23.11 shipped the patch for 2.39.2 since the reddit post you linked. So you’ve got the fix already.

  3. nixos-23.11 recently updated to 2.39.3 anyway, so you definitely already have it fixed.

  4. The problems with multi-device bcachefs go much further than this, and that’s most likely why you’re having trouble mounting it on boot. This is just a limitation in systemd currently . There’s also a nixpkgs issue about it. TL;DR: If you use UUID=... in fstab, systemd wants to wait for only one device and then pass that device alone to the mount CLI, which doesn’t work. If you use /dev/foo:/dev/bar, systemd wants to wait for a single device whose name is /dev/foo:/dev/bar rather than two separate devices. I’m looking into fixes for this problem myself.

  5. Actually, you don’t have to use the lettered names. You can use like /dev/disk/by-id/foo which doesn’t change on reboot. You can’t use /dev/disk/by-uuid though because all the devices share a UUID so only one gets the link in there.

In the meantime, you probably just have to make a custom service that runs the mount command itself. Here’s some more discussion on here about this: How do I mount multiple bcachefs devices on boot?