From 333d4bcf563d8bc341460a5ff5e47c7fa36ddc4a Mon Sep 17 00:00:00 2001
From: Gregor Kleen <gkleen@yggdrasil.li>
Date: Sat, 29 May 2021 15:18:04 +0200
Subject: surtr: zfs snapshots

---
 hosts/surtr/default.nix | 34 +++----------------
 hosts/surtr/zfs.nix     | 89 +++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 94 insertions(+), 29 deletions(-)
 create mode 100644 hosts/surtr/zfs.nix

(limited to 'hosts')

diff --git a/hosts/surtr/default.nix b/hosts/surtr/default.nix
index ba304e22..8cbb51ef 100644
--- a/hosts/surtr/default.nix
+++ b/hosts/surtr/default.nix
@@ -1,7 +1,7 @@
 { flake, pkgs, ... }:
 {
   imports = with flake.nixosModules.systemProfiles; [
-    qemu-guest openssh rebuild-machines
+    qemu-guest openssh rebuild-machines ./zfs.nix
   ];
 
   config = {
@@ -24,7 +24,10 @@
       tmpOnTmpfs = true;
 
       supportedFilesystems = [ "zfs" ];
-      zfs.devNodes = "/dev"; # /dev/vda2 does not show up in /dev/disk/by-id
+      zfs = {
+        enableUnstable = true;
+        devNodes = "/dev"; # /dev/vda2 does not show up in /dev/disk/by-id
+      };
     };
 
     fileSystems = {
@@ -37,33 +40,6 @@
         { device = "/dev/disk/by-label/boot";
           fsType = "vfat";
         };
-
-      "/nix" =
-        { device = "surtr/local/nix";
-          fsType = "zfs";
-        };
-
-      "/root" =
-        { device = "surtr/safe/home-root";
-          fsType = "zfs";
-          neededForBoot = true;
-        };
-
-      "/var/lib/systemd" =
-        { device = "surtr/local/var-lib-systemd";
-          fsType = "zfs";
-          neededForBoot = true;
-        };
-
-      "/var/log" =
-        { device = "surtr/local/var-log";
-          fsType = "zfs";
-        };
-
-      "/home" =
-        { device = "surtr/safe/home";
-          fsType = "zfs";
-        };
     };
 
     networking = {
diff --git a/hosts/surtr/zfs.nix b/hosts/surtr/zfs.nix
new file mode 100644
index 00000000..72cc79e3
--- /dev/null
+++ b/hosts/surtr/zfs.nix
@@ -0,0 +1,89 @@
+{ pkgs, config, ... }:
+let
+  snapshotNames = ["frequent" "hourly" "daily" "monthly" "yearly"];
+  snapshotCount = {
+    frequent = 24;
+    hourly = 24;
+    daily = 30;
+    monthly = 12;
+    yearly = 5;
+  };
+  snapshotTimerConfig = {
+    frequent = { OnCalendar = "*:0/5"; Persistent = true; };
+    hourly = { OnCalendar = "hourly"; Persistent = true; };
+    daily = { OnCalendar = "daily"; Persistent = true; };
+    monthly = { OnCalendar = "monthly"; Persistent = true; };
+    yearly = { OnCalendar = "yearly"; Persistent = true; };
+  };
+  snapshotDescr = {
+    frequent = "few minutes";
+    hourly = "hour";
+    daily = "day";
+    monthly = "month";
+    yearly = "year";
+  };
+
+  zfs = config.boot.zfs.package;
+
+  autosnapPackage = pkgs.zfstools.override { inherit zfs; };
+in {
+  config = {
+    fileSystems = {
+      "/nix" =
+        { device = "surtr/local/nix";
+          fsType = "zfs";
+        };
+
+      "/root" =
+        { device = "surtr/safe/home-root";
+          fsType = "zfs";
+          neededForBoot = true;
+        };
+
+      "/var/lib/systemd" =
+        { device = "surtr/local/var-lib-systemd";
+          fsType = "zfs";
+          neededForBoot = true;
+        };
+
+      "/var/log" =
+        { device = "surtr/local/var-log";
+          fsType = "zfs";
+        };
+
+      "/home" =
+        { device = "surtr/safe/home";
+          fsType = "zfs";
+        };
+    };
+
+    systemd.services =
+      let mkSnapService = snapName: {
+            name = "zfs-snapshot-${snapName}";
+            value = {
+              description = "ZFS auto-snapshot every ${snapshotDescr.${snapName}}";
+              after = [ "zfs-import.target" ];
+              serviceConfig = {
+                Type = "oneshot";
+                ExecStart = "${autosnapPackage}/bin/zfs-auto-snapshot -k -p -u ${snapName} ${toString snapshotCount.${snapName}}";
+              };
+              restartIfChanged = false;
+
+              preStart = ''
+                ${zfs}/bin/zfs set com.sun:auto-snapshot=true surtr/safe
+              '';
+            };
+          };
+      in builtins.listToAttrs (map mkSnapService snapshotNames);
+
+    systemd.timers =
+      let mkSnapTimer = snapName: {
+            name = "zfs-snapshot-${snapName}";
+            value = {
+              wantedBy = [ "timers.target" ];
+              timerConfig = snapshotTimerConfig.${snapName};
+            };
+          };
+      in builtins.listToAttrs (map mkSnapTimer snapshotNames);
+  };
+}
-- 
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