outputs: make compatible with nix run and package lists

[iFreilicht]

This adds new outpus like diskoFormat and diskoFormatNoDeps which are compatible with nix run so you can do something like

nix run .#nixosConfigurations.myhostname.config.system.build.diskoFormatNoDeps

as originally intended in #78, or add disko to your configuration like

environment.systemPackages = [
    config.system.build.diskoFormat
    config.system.build.diskoMount
    config.system.build.diskoDisko
];

as mentioned in #454.

The old outputs are marked as deprecated and a warning like this is shown to the user:

# nix run .#nixosConfigurations.testmachine.config.system.build.mountScript
trace: evaluation warning: 
The output .mountScript is deprecated in favor of .diskoMount and will be removed in
version 2.0.0! To fix this issue, you need to do the following:
  - If you're currently calling "$‍{system.build.mountScript}" as a script,
    use "$‍{system.build.diskoMount}/bin/disko-mount" instead!
  - If you added "system.build.mountScript" to your systemPackages, users.<name>.packages
    or home.packages, or used it with buildEnv or mkShell, this has never worked
    and using "system.build.diskoMount" will fix it.

error: unable to execute '/nix/store/c48m5ffrfzhgsri19b4mlzlbv31ba8yg-disko-mount/bin/disko-mount': Not a directory

Fixes part of #454 (which then only requires proper documentation)
Supersedes #78

@Mic92 I know you suggested in #78 (comment) to use diskoRecreate, but I think as long as we still have --mode disko, we should keep it consistent, so I went for diskoDisko instead. This also helps differentiate this output from the regular disko, which is the CLI.

[Mic92]

Well we can also call it recreate in the cli, while still allowing user the old name. diskoDisko looks weird and the mode disko was never really descriptive to begin with.

[Mic92]

I also would prefer to not have the warning in the beginning until we have also migrated the nixos-anywhere executable to it. We can add the warning later when also nixos-stable no longer has the old nixos-anywhere version to avoid showing users warnings they cannot silence.

[Enzime]

Would love to see a new mode or maybe a flag for the disko/recreate script that doesn’t wipe the partition table as create is kinda idempotent now, I think this mode would be quite useful with nixos-anywhere as a create/update + mount

[Mic92]

@Enzime that mode already exists afaik and it's called format. We just don't advertise it widely as we suspect unsolved edge cases.

[Enzime]

I thought format doesn't mount the filesystems afterwards

[iFreilicht]

I also would prefer to not have the warning in the beginning until we have also migrated the nixos-anywhere executable to it. We can add the warning later when also nixos-stable no longer has the old nixos-anywhere version to avoid showing users warnings they cannot silence.

That's a good point, I'll split those into a separate PR.

Well we can also call it recreate in the cli, while still allowing user the old name. diskoDisko looks weird and the mode disko was never really descriptive to begin with.

That's a good point, and I agree, we should do that. I think I would like to take this opportunity to integrate a solution for #725, which is to simply display a warning when running the "recreate" mode that all disks will be wiped, and asking for confirmation. This dialogue can be skipped with the new flag --force-wipe-disks, and will only appear for --mode recreate, not --mode disko.

Would you agree with that change?

Would love to see a new mode or maybe a flag for the disko/recreate script that doesn’t wipe the partition table as create is kinda idempotent now, I think this mode would be quite useful with nixos-anywhere as a create/update + mount

Hmm, this makes me feel like we might want to make the names of our modes more direct. Instead of inventing new names for joint modes, why don't we just leave the base modes named destroy, format and mount, and allow passing the following values to --mode:

• destroy,format,mount - what disko currently does
• format,mount - the new mode @Enzime suggested
• format - unchanged
• mount - unchanged

The outputs would then be:

• diskoDestroyFormatMountScript
• diskoFormatMountScript
• diskoFormatScript
• diskoMountScript
• diskoDestroyFormatMountScriptNoDeps
• diskoFormatMountScriptNoDeps
• diskoFormatScriptNoDeps
• diskoMountScriptNoDeps

This isn't pretty, but it sure as hell is clear.

[Mic92]

Suggested change

	diskoDisko = (diskoLib.writeCheckedBash { inherit pkgs checked; }) "/bin/disko-disko" ''
	disko = (diskoLib.writeCheckedBash { inherit pkgs checked; }) "/bin/disko-destroy-format-mount" ''

[iFreilicht]

I don't think that's a good idea. We can call the output destroyFormatMount, but just calling it disko makes it too confusing what it's supposed to be, and goes against your other idea of making the outputs a generic interface that has nothing to do with disko directly.

The only output I would expect to be called disko is the CLI.

[iFreilicht]

As I hinted at yesterday, I now used the opportunity to integrate a confirmation dialogue into the modes destroy and destroy,format,mount, which fixes #725.

The existing disko mode is not affected.

I can also split this into a separate PR, but I wanted to avoid having a state on master that is forwards-incompatible with this.

[iFreilicht]

I'll fix the build errors soon, gotta go to bed now, but would appreciate feedback on the changes.

[Mic92]

Sorry, currently busy with NixCon preparation. I would like to get back to this later.

[Lassulus]

changes look good to me, I haven't tested everything though, but it seems like there are no breaking changes and CI is happy.
What would be interesting (in the future in a new PR) would be a real unmount mode, where we don't destroy disks but just umount -Rl and deactivate the LVM/mdadm stuff for affected devices, something similiar to disk-deactivate but less destructive :)

[iFreilicht]

Alright I addressed the last few comments and rebased on master. Once this is merged, I'll open a new issue regarding how we handle the deprecation etc. to make sure an updated version of nixos-anywhere is released before then.