# Moving from CachyOS to NixOS

[nixos-anywhere](https://github.com/nix-community/nixos-anywhere) installs
NixOS from the MacBook over SSH. It switches the running CachyOS into a NixOS
installer in RAM (kexec), wipes the NVMe drive and lays it out as
`hosts/desktop/disko.nix` says, builds the system on the desktop itself and
reboots into it. No USB stick, and nothing Linux gets built on the Mac.

CachyOS and everything on the NVMe drive are gone afterwards. Your home folder
is backed up to the Kingston SATA SSD (`sda`) first, and only what
`restore-filter` lists comes back: it's a fresh start. The other SATA SSD
(`sdb`) is never touched.

## 1. On the desktop (CachyOS)

- [ ] Optional, but the last chance: record WoW's performance to compare
      later. In Faugus, edit Battle.net, turn on MangoHud and add this line to
      the launch arguments:
      `MANGOHUD_CONFIG=read_cfg,output_folder=/home/vizie/benchmarks,log_duration=60,log_interval=0`.
      In game, stand somewhere you can return to (a busy city), keep the camera
      still and press Left Shift+F2. Do it three times. Do the same on NixOS
      later and compare with `~/git/dot/tools/bench-compare`.
- [ ] Quit Signal, Discord, Firefox, Claude and the games, then update the
      backup (only what changed since the last run is copied):

  ```bash
  sudo ~/git/dot/tools/backup-to-sata
  ```

- [ ] Let the Mac log in as root, which nixos-anywhere needs. Paste the Mac's
      public key (`cat ~/.ssh/id_ed25519.pub` on the Mac) into:

  ```bash
  sudo install -d -m700 /root/.ssh && sudo nano /root/.ssh/authorized_keys
  ```

## 2. On the Mac

Needs Nix (with flakes) and the GitHub CLI signed in to your account: `dot`
and `philly` are private, and `gh auth setup-git` lets Nix fetch them. The
Mac's public key must also be in `macKeys` in `hosts/desktop/default.nix`
(committed and pushed), so it can still log in after the install.

```bash
gh auth setup-git
gh repo clone Eiziv/dot ~/dot
```

Check from the Mac that `ssh root@10.0.0.40` logs in. Then install. **This wipes
the desktop's NVMe drive** without asking again:

```bash
nix run github:nix-community/nixos-anywhere -- --flake ~/dot#desktop --build-on remote --copy-host-keys --no-use-machine-substituters root@10.0.0.40
```

It takes a while: the CachyOS kernel's binary cache has been down, so the
kernel compiles on the desktop. `--no-use-machine-substituters` skips that
cache; if it's back up (`curl -sI https://attic.xuyh0120.win/lantian/nix-cache-info`
gives 200), leave the flag out and the kernel downloads instead. The desktop
reboots into NixOS at the end.

## 3. After the reboot

From the Mac (its key is in the config, for root and for you):

```bash
ssh root@10.0.0.40
passwd vizie
mount -o ro /dev/disk/by-label/backup /mnt
/mnt/vizie/git/dot/tools/restore-from-sata
umount /mnt
```

Then log in on the desktop.

## 4. On the new system

- The login screen is the same gtkgreet over the blurred wallpaper.
- Only what `restore-filter` lists came back: app data and logins, SSH keys,
  shell history, `~/git/dot`, Steam's settings and saves. Everything else
  (Downloads, the other repos, CachyOS leftovers) is on the backup drive under
  `vizie/`: `sudo mount -o ro /dev/disk/by-label/backup /mnt` to copy something
  back.
- "Command not found" suggestions need nix-index's database once:
  `nix-index` (takes a few minutes).
- Check the background programs: `systemctl --user list-units --type=service`.

## 5. What changed

What is different from CachyOS, all on purpose:

- **Packages** are generic x86-64 builds, apart from the kernel (Zen 4) and
  proton-cachyos (x86-64-v3). CachyOS rebuilds everything for v3/v4.
- **Snapper** root snapshots are replaced by NixOS generations: each rebuild is
  a boot menu entry. `/home` was never snapshotted on CachyOS either.
- **GTK theme**: set in `modules/home/theming.nix`. nwg-look can't save over
  those files any more.
- **Signal theme** is built into the package: edit, `rebuild`, `config/signal/restart`.
- **Bitwarden** autostart: the same XDG autostart entry, with NixOS's program name.
- **fish**: only CachyOS's default fish config was there, and your shell is zsh,
  so fish isn't set up.
- **vkBasalt's ReShade shaders** in `~/.config/vkBasalt/reshade-shaders` stay in
  your home folder; they aren't in this repo (vkBasalt.conf doesn't use them).
- **vkSumi**: its config is kept, but the layer itself wasn't installed on
  CachyOS (there is no nixpkgs package for it either).

Unchanged on purpose, but worth knowing:

- **kitty's font**: kitty.conf asks for JetBrains Mono, which was never
  installed, so kitty has been showing Noto Sans Mono. That's kept. Add
  `nerd-fonts.jetbrains-mono` to `fonts.packages` in `modules/nixos/desktop.nix`
  to get the font the config names.
- **The login screen opens a kitty terminal** behind gtkgreet
  (`hl.exec_cmd("kitty")` in `config/greetd/hyprland.lua`), running as the
  greeter user. If gtkgreet ever crashed, that shell would be on screen before
  anyone logs in. If it's a leftover from debugging, delete that line.
- **`~/.ssh/authorized_keys`** has a key labelled `chris@echoz.io`, which lets
  that key log in as you over SSH (port 22 is open, as before). It stays in your
  home folder.
- **mDNS** (port 5353) stays closed in the firewall, as ufw had it.
- **sched-ext** schedulers stay off, as before. See the comment in
  `modules/nixos/cachyos.nix` to try one.

## 6. Games

- **Steam**: your settings, Proton versions and game saves (`compatdata`) are
  back. The games in `~/Games/SteamLibrary` and Steam's own library show as
  not installed; install them again. Steam may need the library folder
  re-added (Settings → Storage).
- **WoW**: in Faugus, remove the old Battle.net entry and add Battle.net again
  (Faugus installs it into a new prefix at `~/Games/battlenet`). Pick the same
  runner, `Proton-CachyOS Latest` (it's back in
  `~/.local/share/Steam/compatibilitytools.d`), and the same launch arguments:
  `WINE_SIMULATE_WRITECOPY=1` and `PROTON_ENABLE_WAYLAND=0`. Install WoW, then
  copy your settings and addons back before you start it:

  ```bash
  sudo mount -o ro /dev/disk/by-label/backup /mnt
  cp -a /mnt/wow/{WTF,Interface} ~/Games/battlenet/drive_c/'Program Files (x86)'/'World of Warcraft'/_retail_/
  sudo umount /mnt
  ```

- **OSRS**: install the official Old School RuneScape launcher. Bolt is gone,
  and so is its data.

## 7. Once you're happy

The backup on `sda` stays until you need the drive for something else. It is
the only copy of what wasn't restored, including the repos that exist only
here (`skate3`, `skate-game`, `he60`, `move`, and `Left4Resi`'s uncommitted
changes), so copy out anything you want before reusing the drive. NixOS
doesn't mount it; `sudo mount /dev/disk/by-label/backup /mnt` gets you into it.