WIP: add notes for missing persistence/backup

TODO:
* Look at for more inspiration https://github.com/nix-community/impermanence/pull/108
* Do home-manager
* Common files https://github.com/nix-community/impermanence/issues/10

flake.lock

@@ -145,6 +145,22 @@
         "type": "github"
       }
     },
+    "impermanence": {
+      "locked": {
+        "lastModified": 1697303681,
+        "narHash": "sha256-caJ0rXeagaih+xTgRduYtYKL1rZ9ylh06CIrt1w5B4g=",
+        "owner": "nix-community",
+        "repo": "impermanence",
+        "rev": "0f317c2e9e56550ce12323eb39302d251618f5b5",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-community",
+        "ref": "master",
+        "repo": "impermanence",
+        "type": "github"
+      }
+    },
     "nixpkgs": {
       "locked": {
         "lastModified": 1698611440,
@@ -212,6 +228,7 @@
         "flake-parts": "flake-parts",
         "futils": "futils",
         "home-manager": "home-manager",
+        "impermanence": "impermanence",
         "nixpkgs": "nixpkgs",
         "nur": "nur",
         "pre-commit-hooks": "pre-commit-hooks"

flake.nix

@@ -39,6 +39,13 @@
       };
     };
 
+    impermanence = {
+      type = "github";
+      owner = "nix-community";
+      repo = "impermanence";
+      ref = "master";
+    };
+
     nixpkgs = {
       type = "github";
       owner = "NixOS";

modules/nixos/hardware/bluetooth/default.nix

@@ -18,6 +18,13 @@ in
       services.blueman.enable = true;
     }
 
+    # Persist bluetooth files
+    {
+      my.system.persist.directories = [
+        "/var/lib/bluetooth"
+      ];
+    }
+
     # Support for additional bluetooth codecs
     (lib.mkIf cfg.loadExtraCodecs {
       hardware.pulseaudio = {

modules/nixos/hardware/networking/default.nix

@@ -22,6 +22,11 @@ in
   config = lib.mkMerge [
     (lib.mkIf cfg.wireless.enable {
       networking.networkmanager.enable = true;
+
+      # Persist NetworkManager files
+      my.system.persist.directories = [
+        "/etc/NetworkManager/system-connections"
+      ];
     })
   ];
 }

modules/nixos/services/blog/default.nix

@@ -42,5 +42,12 @@ in
 
     # Those are all subdomains, no problem
     my.services.nginx.virtualHosts = hostsInfo;
+
+    my.system.persist.directories = [
+      "/var/www/blog"
+      "/var/www/cv"
+      "/var/www/dev"
+      "/var/www/key"
+    ];
   };
 }

modules/nixos/services/calibre-web/default.nix

@@ -54,6 +54,11 @@ in
       ];
     };
 
+    my.system.persist.directories = [
+      "/var/lib/${config.services.calibre-web.dataDir}"
+      cfg.libraryPath
+    ];
+
     services.fail2ban.jails = {
       calibre-web = ''
         enabled = true

modules/nixos/services/flood/default.nix

@@ -46,5 +46,9 @@ in
         inherit (cfg) port;
       }
     ];
+
+    my.system.persist.directories = [
+      "/var/lib/${cfg.stateDir}"
+    ];
   };
 }

modules/nixos/services/gitea/default.nix

@@ -135,6 +135,11 @@ in
       ];
     };
 
+    my.system.persist.directories = [
+      config.services.gitea.lfs.contentDir
+      config.services.gitea.repositoryRoot
+    ];
+
     services.fail2ban.jails = {
       gitea = ''
         enabled = true

modules/nixos/services/grocy/default.nix

@@ -36,5 +36,8 @@ in
       forceSSL = true;
       useACMEHost = config.networking.domain;
     };
+
+    # FIXME: backup
+    # FIXME: persistence
   };
 }

modules/nixos/services/indexers/default.nix

@@ -34,6 +34,10 @@ in
           port = jackettPort;
         }
       ];
+
+      my.system.persist.directories = [
+        config.services.jackett.dataDir
+      ];
     })
 
     (lib.mkIf cfg.nzbhydra.enable {
@@ -47,6 +51,10 @@ in
           port = nzbhydraPort;
         }
       ];
+
+      my.system.persist.directories = [
+        config.services.nzbhydra2.dataDir
+      ];
     })
 
     (lib.mkIf cfg.prowlarr.enable {
@@ -61,6 +69,10 @@ in
         }
       ];
 
+      my.system.persist.directories = [
+        "/var/lib/${config.systemd.services.prowlarr.serviceConfig.StateDirectory}"
+      ];
+
       services.fail2ban.jails = {
         prowlarr = ''
           enabled = true

modules/nixos/services/jellyfin/default.nix

@@ -35,5 +35,9 @@ in
         };
       }
     ];
+
+    my.system.persist.directories = [
+      "/var/lib/${config.systemd.services.jellyfin.serviceConfig.StateDirectory}"
+    ];
   };
 }

modules/nixos/services/lohr/default.nix

@@ -104,5 +104,9 @@ in
         inherit (cfg) port;
       }
     ];
+
+    my.system.persist.directories = [
+      "/var/lib/${config.systemd.services.lohr.serviceConfig.StateDirectory}"
+    ];
   };
 }

modules/nixos/services/matrix/default.nix

@@ -257,5 +257,9 @@ in
         config.services.matrix-synapse.dataDir
       ];
     };
+
+    my.system.persist.directories = [
+      config.services.matrix-synapse.dataDir
+    ];
   };
 }

modules/nixos/services/miniflux/default.nix

@@ -49,5 +49,8 @@ in
         inherit (cfg) port;
       }
     ];
+
+    # FIXME: backup
+    # FIXME: persistence
   };
 }

modules/nixos/services/monitoring/default.nix

@@ -131,5 +131,10 @@ in
         inherit (cfg.grafana) port;
       }
     ];
+
+    my.system.persist.directories = [
+      config.services.grafana.dataDir
+      "/var/lib/${config.services.prometheus.stateDir}"
+    ];
   };
 }

modules/nixos/services/navidrome/default.nix

@@ -53,5 +53,9 @@ in
         inherit (cfg) port;
       }
     ];
+
+    my.system.persist.directories = [
+      "/var/lib/${config.systemd.services.navidrome.serviceConfig.StateDirectory}"
+    ];
   };
 }

modules/nixos/services/nextcloud/default.nix

@@ -82,5 +82,10 @@ in
         "${config.services.nextcloud.home}/data/appdata_*/preview"
       ];
     };
+
+    my.system.persist.directories = [
+      config.services.nextcloud.home
+      config.services.nextcloud.datadir
+    ];
   };
 }

modules/nixos/services/nginx/default.nix

@@ -467,5 +467,9 @@ in
         }
       ];
     };
+
+    my.system.persist.directories = [
+      config.users.user.acme.home
+    ];
   };
 }

modules/nixos/services/paperless/default.nix

@@ -164,5 +164,10 @@ in
         config.services.paperless.mediaDir
       ];
     };
+
+    my.system.persist.directories = [
+      config.services.paperless-ng.dataDir
+      config.services.paperless-ng.mediaDir
+    ];
   };
 }

modules/nixos/services/pirate/default.nix

@@ -18,6 +18,11 @@ let
       enable = true;
       group = "media";
     };
+
+    # Thankfully those old style services all define users with homes
+    my.system.persist.directories = [
+      config.users.user.${service}.home
+    ];
   };
 
   mkRedirection = service: {

modules/nixos/services/podgrab/default.nix

@@ -37,5 +37,10 @@ in
         inherit (cfg) port;
       }
     ];
+
+    my.system.persist.directories =
+      builtins.map
+        (d: "/var/lib/${d}")
+        config.systemd.services.podgrab.serviceConfig.StateDirectory;
   };
 }

modules/nixos/services/postgresql-backup/default.nix

@@ -24,5 +24,9 @@ in
         (config.services.postgresqlBackup.location + "/*.prev.sql.gz")
       ];
     };
+
+    my.system.persist.directories = [
+      config.services.postgresqlBackup.location
+    ];
   };
 }

modules/nixos/services/postgresql/default.nix

@@ -18,6 +18,13 @@ in
       };
     })
 
+    # Only persist directory if the actual service is enabled
+    (lib.mkIf config.services.postgresql.enable {
+      my.system.persist.directories = [
+        config.services.postgresql.dataDir
+      ];
+    })
+
     # Taken from the manual
     (lib.mkIf cfg.upgradeScript {
       containers.temp-pg.config.services.postgresql = {

modules/nixos/services/quassel/default.nix

@@ -46,5 +46,9 @@ in
       # Because Quassel does not use the socket, I simply trust its connection
       authentication = "host quassel quassel localhost trust";
     };
+
+    my.system.persist.directories = [
+      config.services.quassel.dataDir
+    ];
   };
 }

modules/nixos/services/rss-bridge/default.nix

@@ -20,5 +20,9 @@ in
       forceSSL = true;
       useACMEHost = config.networking.domain;
     };
+
+    my.system.persist.directories = [
+      config.services.rss-bridge.dataDir
+    ];
   };
 }

modules/nixos/services/sabnzbd/default.nix

@@ -25,6 +25,10 @@ in
       }
     ];
 
+    my.system.persist.files = [
+      config.services.sabnzbd.configFile
+    ];
+
     services.fail2ban.jails = {
       sabnzbd = ''
         enabled = true

modules/nixos/services/ssh-server/default.nix

@@ -20,6 +20,14 @@ in
       };
     };
 
+    # Persist SSH keys
+    my.system.persist.files = [
+      "/etc/ssh/ssh_host_ed25519_key"
+      "/etc/ssh/ssh_host_ed25519_key.pub"
+      "/etc/ssh/ssh_host_rsa_key"
+      "/etc/ssh/ssh_host_rsa_key.pub"
+    ];
+
     # Opens the relevant UDP ports.
     programs.mosh.enable = true;
   };

modules/nixos/services/tandoor-recipes/default.nix

@@ -76,5 +76,8 @@ in
         inherit (cfg) port;
       }
     ];
+
+    # FIXME: backup
+    # FIXME: persistence
   };
 }

modules/nixos/services/transmission/default.nix

@@ -91,5 +91,9 @@ in
       allowedTCPPorts = [ cfg.peerPort ];
       allowedUDPPorts = [ cfg.peerPort ];
     };
+
+    my.system.persist.directories = [
+      config.services.transmission.home
+    ];
   };
 }

modules/nixos/services/vikunja/default.nix

@@ -119,5 +119,7 @@ in
         config.services.vikunja.settings.files.basepath
       ];
     };
+
+    # FIXME: persistence
   };
 }

modules/nixos/system/default.nix

@@ -9,6 +9,7 @@
     ./language
     ./nix
     ./packages
+    ./persist
     ./podman
     ./printing
     ./users

modules/nixos/system/persist/default.nix

@@ -0,0 +1,68 @@
+# Ephemeral root configuration
+{ config, inputs, lib, ... }:
+let
+  cfg = config.my.system.persist;
+in
+{
+  imports = [
+    inputs.impermanence.nixosModules.impermanence
+  ];
+
+  options.my.system.persist = with lib; {
+    enable = mkEnableOption "stateless system configuration";
+
+    mountPoint = lib.mkOption {
+      type = types.str;
+      default = "/persistent";
+      example = "/etc/nix/persist";
+      description = ''
+        Which mount point should be used to persist this system's files and
+        directories.
+      '';
+    };
+
+    files = lib.mkOption {
+      type = with types; listOf str;
+      default = [ ];
+      example = [
+        "/etc/nix/id_rsa"
+      ];
+      description = ''
+        Additional files in the root to link to persistent storage.
+      '';
+    };
+
+    directories = lib.mkOption {
+      type = with types; listOf str;
+      default = [ ];
+      example = [
+        "/var/lib/libvirt"
+      ];
+      description = ''
+        Additional directories in the root to link to persistent storage.
+      '';
+    };
+  };
+
+  config = lib.mkIf cfg.enable {
+    environment.persistence."${cfg.mountPoint}" = {
+      files = [
+        "/etc/machine-id"
+      ]
+      ++ cfg.files
+      ;
+
+      directories = [
+        "/etc/nixos"
+        "/var/log"
+        "/var/lib/systemd/coredump"
+      ]
+      ++ (lib.optionals config.virtualisation.docker.enable [
+        "/var/lib/docker"
+      ])
+      # FIXME: podman
+      ++ cfg.directories
+      ;
+    };
+  };
+}