modules/backup: init

Co-authored-by: b12f <b12f@noreply.git.pub.solar>
Co-authored-by: Hendrik Sokolowski <hensoko@noreply.git.pub.solar>

hosts/default.nix

@@ -11,6 +11,7 @@
           self.nixosModules.unlock-zfs-on-boot
           self.nixosModules.core
           self.nixosModules.docker
+          self.nixosModules.backups
 
           self.nixosModules.nginx
           self.nixosModules.collabora
@@ -49,6 +50,7 @@
           ./flora-6
           self.nixosModules.overlays
           self.nixosModules.core
+          self.nixosModules.backups
 
           self.nixosModules.keycloak
           self.nixosModules.caddy
@@ -68,6 +70,7 @@
           self.nixosModules.overlays
           self.nixosModules.unlock-zfs-on-boot
           self.nixosModules.core
+          self.nixosModules.backups
           self.nixosModules.mail
           self.nixosModules.prometheus-exporters
           self.nixosModules.promtail
@@ -83,6 +86,7 @@
           ./tankstelle
           self.nixosModules.overlays
           self.nixosModules.core
+          self.nixosModules.backups
           self.nixosModules.prometheus-exporters
           self.nixosModules.promtail
         ];

modules/backups/default.nix

@@ -0,0 +1,274 @@
+{
+  flake,
+  config,
+  lib,
+  pkgs,
+  ...
+}:
+let
+  utils = import "${flake.inputs.nixpkgs}/nixos/lib/utils.nix" {
+    inherit lib;
+    inherit config;
+    inherit pkgs;
+  };
+  # Type for a valid systemd unit option. Needed for correctly passing "timerConfig" to "systemd.timers"
+  inherit (utils.systemdUtils.unitOptions) unitOption;
+  inherit (lib)
+    literalExpression
+    mkOption
+    mkPackageOption
+    types
+    ;
+in
+{
+  options.pub-solar-os.backups = {
+    repos = mkOption {
+      description = ''
+        Configuration of Restic repositories.
+      '';
+      type = types.attrsOf (
+        types.submodule (
+          { name, ... }:
+          {
+            options = {
+              passwordFile = mkOption {
+                type = types.str;
+                description = ''
+                  Read the repository password from a file.
+                '';
+                example = "/etc/nixos/restic-password";
+              };
+
+              repository = mkOption {
+                type = with types; nullOr str;
+                default = null;
+                description = ''
+                  repository to backup to.
+                '';
+                example = "sftp:backup@192.168.1.100:/backups/${name}";
+              };
+            };
+          }
+        )
+      );
+
+      default = { };
+      example = {
+        remotebackup = {
+          repository = "sftp:backup@host:/backups/home";
+          passwordFile = "/etc/nixos/secrets/restic-password";
+        };
+      };
+    };
+
+    backups = mkOption {
+      description = ''
+        Periodic backups to create with Restic.
+      '';
+      type = types.attrsOf (
+        types.submodule (
+          { name, ... }:
+          {
+            options = {
+              paths = mkOption {
+                # This is nullable for legacy reasons only. We should consider making it a pure listOf
+                # after some time has passed since this comment was added.
+                type = types.nullOr (types.listOf types.str);
+                default = [ ];
+                description = ''
+                  Which paths to backup, in addition to ones specified via
+                  `dynamicFilesFrom`.  If null or an empty array and
+                  `dynamicFilesFrom` is also null, no backup command will be run.
+                   This can be used to create a prune-only job.
+                '';
+                example = [
+                  "/var/lib/postgresql"
+                  "/home/user/backup"
+                ];
+              };
+
+              exclude = mkOption {
+                type = types.listOf types.str;
+                default = [ ];
+                description = ''
+                  Patterns to exclude when backing up. See
+                  https://restic.readthedocs.io/en/latest/040_backup.html#excluding-files for
+                  details on syntax.
+                '';
+                example = [
+                  "/var/cache"
+                  "/home/*/.cache"
+                  ".git"
+                ];
+              };
+
+              timerConfig = mkOption {
+                type = types.nullOr (types.attrsOf unitOption);
+                default = {
+                  OnCalendar = "daily";
+                  Persistent = true;
+                };
+                description = ''
+                  When to run the backup. See {manpage}`systemd.timer(5)` for
+                  details. If null no timer is created and the backup will only
+                  run when explicitly started.
+                '';
+                example = {
+                  OnCalendar = "00:05";
+                  RandomizedDelaySec = "5h";
+                  Persistent = true;
+                };
+              };
+
+              user = mkOption {
+                type = types.str;
+                default = "root";
+                description = ''
+                  As which user the backup should run.
+                '';
+                example = "postgresql";
+              };
+
+              extraBackupArgs = mkOption {
+                type = types.listOf types.str;
+                default = [ ];
+                description = ''
+                  Extra arguments passed to restic backup.
+                '';
+                example = [ "--exclude-file=/etc/nixos/restic-ignore" ];
+              };
+
+              extraOptions = mkOption {
+                type = types.listOf types.str;
+                default = [ ];
+                description = ''
+                  Extra extended options to be passed to the restic --option flag.
+                '';
+                example = [ "sftp.command='ssh backup@192.168.1.100 -i /home/user/.ssh/id_rsa -s sftp'" ];
+              };
+
+              initialize = mkOption {
+                type = types.bool;
+                default = false;
+                description = ''
+                  Create the repository if it doesn't exist.
+                '';
+              };
+
+              pruneOpts = mkOption {
+                type = types.listOf types.str;
+                default = [ ];
+                description = ''
+                  A list of options (--keep-\* et al.) for 'restic forget
+                  --prune', to automatically prune old snapshots.  The
+                  'forget' command is run *after* the 'backup' command, so
+                  keep that in mind when constructing the --keep-\* options.
+                '';
+                example = [
+                  "--keep-daily 7"
+                  "--keep-weekly 5"
+                  "--keep-monthly 12"
+                  "--keep-yearly 75"
+                ];
+              };
+
+              runCheck = mkOption {
+                type = types.bool;
+                default = (builtins.length config.pub-solar-os.backups.backups.${name}.checkOpts > 0);
+                defaultText = literalExpression ''builtins.length config.services.backups.${name}.checkOpts > 0'';
+                description = "Whether to run the `check` command with the provided `checkOpts` options.";
+                example = true;
+              };
+
+              checkOpts = mkOption {
+                type = types.listOf types.str;
+                default = [ ];
+                description = ''
+                  A list of options for 'restic check'.
+                '';
+                example = [ "--with-cache" ];
+              };
+
+              dynamicFilesFrom = mkOption {
+                type = with types; nullOr str;
+                default = null;
+                description = ''
+                  A script that produces a list of files to back up.  The
+                  results of this command are given to the '--files-from'
+                  option. The result is merged with paths specified via `paths`.
+                '';
+                example = "find /home/matt/git -type d -name .git";
+              };
+
+              backupPrepareCommand = mkOption {
+                type = with types; nullOr str;
+                default = null;
+                description = ''
+                  A script that must run before starting the backup process.
+                '';
+              };
+
+              backupCleanupCommand = mkOption {
+                type = with types; nullOr str;
+                default = null;
+                description = ''
+                  A script that must run after finishing the backup process.
+                '';
+              };
+
+              package = mkPackageOption pkgs "restic" { };
+
+              createWrapper = lib.mkOption {
+                type = lib.types.bool;
+                default = true;
+                description = ''
+                  Whether to generate and add a script to the system path, that has the same environment variables set
+                  as the systemd service. This can be used to e.g. mount snapshots or perform other opterations, without
+                  having to manually specify most options.
+                '';
+              };
+            };
+          }
+        )
+      );
+      default = { };
+      example = {
+        localbackup = {
+          paths = [ "/home" ];
+          exclude = [ "/home/*/.cache" ];
+          initialize = true;
+        };
+        remotebackup = {
+          paths = [ "/home" ];
+          extraOptions = [
+            "sftp.command='ssh backup@host -i /etc/nixos/secrets/backup-private-key -s sftp'"
+          ];
+          timerConfig = {
+            OnCalendar = "00:05";
+            RandomizedDelaySec = "5h";
+          };
+        };
+      };
+    };
+  };
+
+  config = {
+    services.restic.backups =
+      let
+        repos = config.pub-solar-os.backups.repos;
+        backups = config.pub-solar-os.backups.backups;
+
+        storeNames = builtins.attrNames repos;
+        backupNames = builtins.attrNames backups;
+
+        createBackups =
+          backupName:
+          map (storeName: {
+            name = "${backupName}-${storeName}";
+            value = repos."${storeName}" // backups."${backupName}";
+          }) storeNames;
+
+      in
+      builtins.listToAttrs (lib.lists.flatten (map createBackups backupNames));
+  };
+}