Impermanence: the persistence list, written before it is switched on

modules/home/persistence.nix. NOT active: nothing is wiped today.

Where this standsCopy Anchor Link

The layout is ready since the install (@persist exists and is empty, see disko), and the plan in docs/open-items.md is unchanged: the root goes ephemeral first, the home after. What this module adds is the HOME's list, written and checked now, so the day it is switched on is a wiring change and not a guessing session. It only turns on when I say so.

The model: folders whole, app state by nameCopy Anchor Link

The first idea was a file-by-file triage of the home (an inventory of 359 entries and 459.5 GiB on 28/10/2026). It was dropped the same day: deciding every file is work that never ends, and it is the wrong unit.

• The user folders persist WHOLE: the XDG ones (Desktop, Documents, Downloads, Music, Pictures, Videos, declared with xdg.userDirs in modules/home/desktop/xdg.nix) plus Projects, Games, Archive, CS2-Saves-Backup and the Dropbox data. Keeping them tidy is a habit, and what matters goes to Dropbox and the Obsidian vault in it.
• Hidden state is listed BY APP: about a hundred entries (keys, game prefixes, browser profiles, AI tool sessions, app logins), each with a one-line reason in the module.
• Everything else is wiped at boot: caches, leftovers of removed apps, loose files at the root of the home. That is the point: a file outside the folders is a file that was never filed.

The entries use the same shapes as nix-community/impermanence ("path" or { directory; mode; }, relative to the home), so they can be handed to environment.persistence."/persist".users.v1cferr as they are.

persist-diff: what would be lostCopy Anchor Link

persist-diff            # every path in ~ the list does not cover, biggest first, plus a total

It walks the home, descends only into folders that hold a persisted path, and skips what comes back on its own: home-manager links into the store, folders made only of them, and the rclone mounts. Read-only, about 8 s.

MEASURED on 28/10/2026, with the list as committed: 41 GiB in 143 paths would not survive. 19 GiB of it is ~/.cache, and most of the rest is other caches (pnpm, npm, cargo, .vscode-server), the Chrome stable profile (the app is no longer installed) and leftovers of apps removed long ago. The run is also what surfaced the cases the list must not miss:

• Hand-written user units: the acuttis-point* services and timers in ~/.config/systemd/user are not declared anywhere, so they would vanish. They belong in Nix before the switch, not in this list (home-manager owns that folder).
• Loose secrets at the root of the home (age-backup-key.txt, wg0.conf, a router backup): they belong in the Bitwarden vault or sops, not in a persisted folder.

The rule for switching on: run it, and when what it prints is only garbage for a few weeks running, the list is right.

Turning it on (later, and only when I decide)Copy Anchor Link

1. Add nix-community/impermanence as a flake input and import its NixOS module.
2. Root first: wipe @ at boot from a blank snapshot and declare the system list (/var/lib, the machine id, NetworkManager connections and so on). That list does not exist yet.
3. Home after: hand config.home-manager.users.v1cferr.my.persist to environment.persistence."/persist".users.v1cferr, move the data into /persist/home/v1cferr once, and only then wipe @home.

Two things to settle at step 3: the nested subvolumes from home-subvolumes.nix (game libraries and VM images) need their own answer, because a bind mount over a subvolume is not the same as keeping it, and a persisted folder is not a backed-up one (~/Downloads is still outside restic).