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Impermanence & Persistence

The root filesystem is a volatile tmpfs, rebuilt clean on every boot via nix-community/impermanence. Nothing outside the Nix store and explicitly-declared persistence survives a reboot.

graph LR
    BOOT["boot"] --> TMP["/ (tmpfs)<br/>wiped clean"]
    PERSIST["/persist<br/>real disk"] -->|bind / symlink| TMP
    REPO["/persist/.../.nix-config/dots"] -->|mkOutOfStoreSymlink| CFG["~/.config/*"]
    EDIT["edit dotfile"] --> REPO
    REPO -.live, no rebuild.-> CFG

What persists

Persistence is declared per-user in home/persist.nix under home.persistence."/persist". Categories include:

Category Examples
Credentials .ssh, .gnupg, .config/sops, .local/share/keyrings
Tooling .cargo, .rustup, .npm, .local/share/go, .foundry, .solc-select
App state .config/BraveSoftware, .config/VSCodium, .ollama, .claude, .var/app, .local/share/noctalia, .local/state/noctalia
Caches .cache/pip, .cache/noctalia, .cache/nvidia, .cache/llmfit
Home dirs Documents, Pictures, Downloads, Projects, CodeRepo, AppImage
Memory tool .config/memd, .local/state/memd
Single file .claude.json (Claude Code state, lives outside ~/.claude)

Cache root lives off the tmpfs

xdg.cacheHome is redirected to ~/Storage/.cache (see home/persist.nix / home/default.nix), so caches don't fill the ~4 GB tmpfs root. The .cache/* persistence entries above remain as a safety net for apps that hardcode ~/.cache and ignore XDG. (.config/niri and .config/noctalia are not in this list — they are out-of-store symlinks, covered below.)

User dotfiles are not copied into the Nix store. Instead, home/persist.nix maps them with config.lib.file.mkOutOfStoreSymlink from the repo checkout into ~/.config/:

xdg.configFile."niri".source =
  config.lib.file.mkOutOfStoreSymlink
    "/persist${config.home.homeDirectory}/.nix-config/dots/niri";

Why out-of-store

Edits to the tracked dotfiles take effect immediately — inotify hot-reload works across the symlink — without a home-manager rebuild, while the files remain version-controlled. This is the same philosophy applied to the agent tooling binaries in home/scripts.nix.

The ~/volnix alias

home/persist.nix also creates a non-hidden symlink ~/volnix → /persist$HOME/.nix-config. The Antigravity CLI rejects hidden paths as workspace folders, so the agent tether delegates with ~/volnix as the working directory.

Secrets never live in dots/

dots/ is published in the public repo. Secrets belong only in nixos/host-secrets.yaml / nixos/vm-secrets.yaml (sops-encrypted) or under /persist (never git-tracked). See Secrets.