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

Or simply apply a theme you know is good: nomarchy-theme-sync apply tokyo-night. 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 home-update).

Your flake checkout is a git repo, and with auto-commit enabled every apply is a commit: git -C ~/.nomarchy log to see what changed, git revert the culprit, then home-update.

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; the last 10 generations are kept). 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 sys-rebuild.

4. 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 › Snapshots (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.

5. 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 §4. If you get this far with something Nomarchy shipped broken, please file it.