Nomarchy/docs/RECOVERY.md

Recovery runbook — when something breaks

Ordered from "the desktop looks wrong" to "the machine won't boot". Everything here already ships on an installed machine — you don't need a live USB until the last resort. The theme is always the same: nothing in Nomarchy is destroyed by a bad change — every rebuild is a NixOS / Home Manager generation you can step back to, and (on BTRFS installs) snapper keeps file-level history on top.

If the graphical session is unusable, a text console is one keystroke away: Ctrl+Alt+F2 gives a TTY login (the session itself runs on tty1); log in with your normal user.

1. A theme or desktop change broke the session

Theme applies and home-update are Home Manager switches — one generation each, so the previous desktop is still on disk:

home-manager generations          # newest first, one per theme/HM change
/nix/store/…-home-manager-generation/activate   # run the one you want

The same picker lives in the menu: System › Recovery › Desktop generation lists the recent Home Manager generations — pick one and it activates. System-level undo is System › Recovery › System boot generation (boot menu) or Files (BTRFS) (snapper).

Or simply apply a theme you know is good: nomarchy-state-sync apply boreal (or any preset). If a switch failed halfway, the state file is written before the rebuild — fix the cause and re-run home-manager switch --flake ~/.nomarchy (or nomarchy-home).

Your flake checkout is a git repo, and with auto-commit enabled every apply is a commit — and every nomarchy-pull/-rebuild/-home first sweeps pending hand edits into one, so history mirrors your generations: git -C ~/.nomarchy log to see what changed, git revert the culprit, then nomarchy-home.

2. The desktop won't start at all

Greeter loops, black screen after the password, session exits straight back to tuigreet — from the Ctrl+Alt+F2 TTY:

journalctl -b -u greetd           # did the session command launch?
journalctl --user -b              # Hyprland + the user services

• Rolling back the desktop half is §1 (works from the TTY).
• If greetd/tuigreet itself is broken, that's system-side → §3.
• In a VM, a black screen is almost always missing guest OpenGL, not your config — see docs/TESTING.md §5.
• First boot after an install came up unthemed: read /var/log/nomarchy-hm-preactivate.log on the installed system.

3. A system change broke it — boot an older generation

Reboot and pick an older NixOS generation in the systemd-boot menu (hold a key during firmware handoff if the menu doesn't linger). That boots yesterday's system unchanged.

Booting an old generation is temporary — the default entry is still the broken one. Make the fix stick from the working boot: revert the change in ~/.nomarchy (git -C ~/.nomarchy revert … or edit system.nix back), then nomarchy-rebuild.

How long generations stick around (and how cleanup works) is §4 below.

4. How generations are kept (and cleaned up)

Every nomarchy-rebuild and nomarchy-home (and every theme switch) leaves a generation — a full previous system or desktop you can roll back to (§1 and §3, and System › Recovery). Those take disk space until they are removed.

Nomarchy prunes them automatically once a week with a policy designed not to strand you without rollback:

Rule	Meaning
Age	Generations older than 14 days are eligible for removal.
Safety floor	Always keep the current generation and at least 3 past ones — even if those three are older than 14 days.
Both halves	The same rule applies independently to the system (boot menu) and to Home Manager (desktop) profiles.

So a busy machine that rebuilds often can still free old junk after two weeks, while a rarely rebuilt laptop never drops below four usable system gens (current + three past) or four desktop gens.

What you do not need to do: run aggressive nix-collect-garbage -d day to day — that can delete all old generations and wipe the floor. The weekly timer already reclaims store paths after a careful prune.

Manual control:

sudo nomarchy-gen-prune --dry-run   # list what would be deleted
sudo nomarchy-gen-prune             # prune now (same rules as the timer)
systemctl status nomarchy-gen-prune.timer

After a system prune the boot menu is refreshed so removed generations no longer appear as boot entries.

5. Files went missing or wrong — snapshots (BTRFS installs)

With nomarchy.system.snapper.enable (the installer's default on BTRFS), the root filesystem has hourly/daily history, and nixos-rebuild-snap leaves a snapshot right before a rebuild:

• GUI: menu › System › Recovery › Files (BTRFS) (btrfs-assistant; expects a polkit password prompt).
• Terminal/SSH: sudo nomarchy-snapshots — browse a snapshot's diff, restore changed files (snapper undochange), or roll the whole root back to a snapshot and reboot. Both destructive actions sit behind a typed-yes confirmation.

Snapshots are the undo for data on disk; the Nix config model is undone by generations (§1/§3) — use each for its half.

6. Last resort — from the outside

Boot the Nomarchy ISO (any NixOS ISO works), then:

sudo mount /dev/<root> /mnt        # + /mnt/boot; LUKS: cryptsetup open first
sudo nixos-enter --root /mnt       # chroot with nix available

From there you have the full toolbox: nixos-rebuild boot --flake /home/<you>/.nomarchy#default after fixing the flake, or snapper from §5. If you get this far with something Nomarchy shipped broken, please file it.