zfsborg

modules/base/default.nix

@@ -9,6 +9,7 @@
     ./sshd
     ./initrd
     ./snapshot
+    ./zfsborg
   ];
 
   options.mj = {

modules/base/zfsborg/default.nix

@@ -0,0 +1,92 @@
+{
+  config,
+  lib,
+  pkgs,
+  myData,
+  ...
+}: let
+  mountLatest = mountpoint: zfs_name: ''
+    set -euo pipefail
+    ${pkgs.util-linux}/bin/umount ${mountpoint}/.snapshot-latest &>/dev/null || :
+    mkdir -p ${mountpoint}/.snapshot-latest
+    ${pkgs.util-linux}/bin/mount -t zfs $(${pkgs.zfs}/bin/zfs list -H -t snapshot -o name ${zfs_name} | sort | tail -1) ${mountpoint}/.snapshot-latest
+  '';
+
+  umountLatest = mountpoint: ''
+    exec ${pkgs.util-linux}/bin/umount ${mountpoint}/.snapshot-latest
+  '';
+in {
+  options.mj.base.zfsborg = {
+    enable = lib.mkEnableOption "backup zfs snapshots with borg";
+
+    repo = with lib.types; lib.mkOption {type = str;};
+    passwdPath = with lib.types; lib.mkOption {type = str;};
+
+    mountpoints = lib.mkOption {
+      default = {};
+      type = with lib.types;
+        attrsOf (submodule (
+          {...}: {
+            options = {
+              paths = lib.mkOption {type = listOf path;};
+              patterns = lib.mkOption {
+                type = listOf str;
+                default = [];
+              };
+              backup_at = lib.mkOption {type = str;};
+            };
+          }
+        ));
+    };
+  };
+
+  config = lib.mkIf config.mj.base.zfsborg.enable {
+    systemd.services."zfsborg-snapshot-dirs" = let
+      mountpoints = lib.unique (lib.attrNames config.mj.base.zfsborg.mountpoints);
+    in {
+      description = "zfsborg prepare snapshot directories";
+      wantedBy = ["multi-user.target"];
+      serviceConfig = {
+        Type = "oneshot";
+        ExecStart =
+          builtins.map
+          (d: "${pkgs.coreutils}/bin/mkdir -p ${d}/.snapshot-latest")
+          mountpoints;
+        RemainAfterExit = true;
+      };
+    };
+
+    services.borgbackup.jobs = lib.mapAttrs' (mountpoint: attrs: let
+      fs = builtins.getAttr mountpoint config.fileSystems;
+    in
+      assert fs.fsType == "zfs"; {
+        name = lib.strings.sanitizeDerivationName mountpoint;
+        value =
+          {
+            doInit = true;
+            repo = config.mj.base.zfsborg.repo;
+            encryption = {
+              mode = "repokey-blake2";
+              passCommand = "cat ${config.mj.base.zfsborg.passwdPath}";
+            };
+            paths = attrs.paths;
+            extraArgs = "--remote-path=borg1";
+            compression = "auto,lzma";
+            startAt = attrs.backup_at;
+            readWritePaths = let p = mountpoint + "/.snapshot-latest"; in [p];
+            preHook = mountLatest mountpoint fs.device;
+            postHook = umountLatest mountpoint;
+            prune.keep = {
+              within = "1d";
+              daily = 7;
+              weekly = 4;
+              monthly = 3;
+            };
+          }
+          // lib.optionalAttrs (attrs ? patterns) {
+            patterns = attrs.patterns;
+          };
+      })
+    config.mj.base.zfsborg.mountpoints;
+  };
+}