nixos/restic: init (#38948)

nixos/modules/module-list.nix

@@ -166,6 +166,7 @@
   ./services/backup/crashplan-small-business.nix
   ./services/backup/mysql-backup.nix
   ./services/backup/postgresql-backup.nix
+  ./services/backup/restic.nix
   ./services/backup/rsnapshot.nix
   ./services/backup/tarsnap.nix
   ./services/backup/znapzend.nix

nixos/modules/services/backup/restic.nix

@@ -0,0 +1,150 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+{
+  options.services.restic.backups = mkOption {
+    description = ''
+      Periodic backups to create with Restic.
+    '';
+    type = types.attrsOf (types.submodule ({ name, config, ... }: {
+      options = {
+        passwordFile = mkOption {
+          type = types.str;
+          description = ''
+            Read the repository password from a file.
+          '';
+          example = "/etc/nixos/restic-password";
+
+        };
+
+        repository = mkOption {
+          type = types.str;
+          description = ''
+            repository to backup to.
+          '';
+          example = "sftp:backup@192.168.1.100:/backups/${name}";
+        };
+
+        paths = mkOption {
+          type = types.listOf types.str;
+          default = [];
+          description = ''
+            Which paths to backup.
+          '';
+          example = [
+            "/var/lib/postgresql"
+            "/home/user/backup"
+          ];
+        };
+
+        timerConfig = mkOption {
+          type = types.attrsOf types.str;
+          default = {
+            OnCalendar = "daily";
+          };
+          description = ''
+            When to run the backup. See man systemd.timer for details.
+          '';
+          example = {
+            OnCalendar = "00:05";
+            RandomizedDelaySec = "5h";
+          };
+        };
+
+        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.
+          '';
+        };
+      };
+    }));
+    default = {};
+    example = {
+      localbackup = {
+        paths = [ "/home" ];
+        repository = "/mnt/backup-hdd";
+        passwordFile = "/etc/nixos/secrets/restic-password";
+        initialize = true;
+      };
+      remotebackup = {
+        paths = [ "/home" ];
+        repository = "sftp:backup@host:/backups/home";
+        passwordFile = "/etc/nixos/secrets/restic-password";
+        extraOptions = [
+          "sftp.command='ssh backup@host -i /etc/nixos/secrets/backup-private-key -s sftp'"
+        ];
+        timerConfig = {
+          OnCalendar = "00:05";
+          RandomizedDelaySec = "5h";
+        };
+      };
+    };
+  };
+
+  config = {
+    systemd.services =
+      mapAttrs' (name: backup:
+        let
+          extraOptions = concatMapStrings (arg: " -o ${arg}") backup.extraOptions;
+          connectTo = elemAt (splitString ":" backup.repository) 1;
+          resticCmd = "${pkgs.restic}/bin/restic${extraOptions}";
+        in nameValuePair "restic-backups-${name}" ({
+          environment = {
+            RESTIC_PASSWORD_FILE = backup.passwordFile;
+            RESTIC_REPOSITORY = backup.repository;
+          };
+          path = with pkgs; [
+            openssh
+          ];
+          restartIfChanged = false;
+          serviceConfig = {
+            Type = "oneshot";
+            ExecStart = "${resticCmd} backup ${concatStringsSep " " backup.extraBackupArgs} ${concatStringsSep " " backup.paths}";
+            User = backup.user;
+          };
+        } // optionalAttrs backup.initialize {
+          preStart = ''
+            ${resticCmd} snapshots || ${resticCmd} init
+          '';
+        })
+      ) config.services.restic.backups;
+    systemd.timers =
+      mapAttrs' (name: backup: nameValuePair "restic-backups-${name}" {
+        wantedBy = [ "timers.target" ];
+        timerConfig = backup.timerConfig;
+      }) config.services.restic.backups;
+  };
+}