2 files changed, 55 insertions, 0 deletions

diff --git a/custom/btrfs-snapshots.nix b/custom/btrfs-snapshots.nix
new file mode 100644
index 00000000..7caf7a30
--- /dev/null
+++ b/custom/btrfs-snapshots.nix
@@ -0,0 +1,52 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+  cfg = config.services.btrfs-snapshots;
+
+  snapshotMount = str: "${cfg.mountPoint}/${cfg.mountPrefix}${str}"
+in {
+  options = {
+
+    services.btrfs-snapshots = {
+      enable = mkEnableOption "btrfs snapshot unit";   
+
+      mountPoint = mkOption {
+        type = types.path;
+        default = "/mnt";
+      };
+
+      mountPrefix = mkOption {
+        type = types.str;
+        default = "snapshot-";
+      };
+
+      readOnly = mkOption {
+        type = types.bool;
+        default = true;
+      };
+    };
+
+  };
+
+  
+  config = mkIf cfg.enable {
+
+    systemd.services."btrfs-snapshot@" = {
+      enable = true;
+      path = with pkgs; [btrfs-progs];
+
+      unitConfig = {
+        AssertPathIsDirectory = ${cfg.mountPoint};
+      };
+
+      serviceConfig = with pkgs; {
+        ExecStart = "${btrfs-progs}/bin/btrfs subvolume snapshot ${optionalString cfg.readOnly "-r"} %f ${snapshotMount "%i"}";
+        RemainAfterExit = true;
+        ExecStop = "${btrfs-progs}/bin/btrfs subvolume delete ${snapshotMount "%i"}";
+      };
+    };
+
+  };
+}
diff --git a/hel.nix b/hel.nix
index ba86b1e4..8e1462d9 100644
--- a/hel.nix
+++ b/hel.nix
@@ -14,6 +14,7 @@
       ./custom/tinc/def.nix
       ./custom/tinc/yggdrasil.nix
       ./custom/uucp.nix
+      ./custom/btrfs-snapshots.nix
     ];
 
   system.stateVersion = "16.09";
@@ -515,5 +516,7 @@
   systemd.targets."multi-user".wants = ["gpscfg.timer"];
 
   systemd.services."NetworkManager-wait-online".enable = true;
+
+  services.btrfs-snapshots.enable = true;
 }