From 6e0af2ca7a4fe0ea216f26adc87e590b233c7b83 Mon Sep 17 00:00:00 2001
From: Price Hiller <price@orion-technologies.io>
Date: Sun, 25 Aug 2024 00:26:25 -0500
Subject: [PATCH] refactor(hosts/luna): use btrfs-rollback service for handling
 rollbacks

---
 flake.nix              |  1 +
 hosts/luna/os/boot.nix | 62 ++++++------------------------------------
 2 files changed, 10 insertions(+), 53 deletions(-)

diff --git a/flake.nix b/flake.nix
index db0f5293..3e719efc 100644
--- a/flake.nix
+++ b/flake.nix
@@ -258,6 +258,7 @@
               };
               modules = [
                 defaults
+                ./modules/btrfs-rollback.nix
                 inputs.impermanence.nixosModules.impermanence
                 inputs.agenix.nixosModules.default
                 inputs.disko.nixosModules.disko
diff --git a/hosts/luna/os/boot.nix b/hosts/luna/os/boot.nix
index c2abd14e..67d932b4 100644
--- a/hosts/luna/os/boot.nix
+++ b/hosts/luna/os/boot.nix
@@ -1,8 +1,15 @@
-{ modulesPath, pkgs, ... }:
+{ modulesPath, ... }:
 {
 
   imports = [ (modulesPath + "/installer/scan/not-detected.nix") ];
 
+  services.btrfs-rollback = {
+    enable = true;
+    diskLabel = "NixOS-Primary";
+    subvolume = "root";
+    snapshot = "root-base";
+  };
+
   boot = {
     tmp = {
       useTmpfs = true;
@@ -24,58 +31,7 @@
         "sd_mod"
       ];
       kernelModules = [ ];
-      systemd = {
-        enable = true;
-        initrdBin = [
-          pkgs.libuuid
-          pkgs.gawk
-        ];
-        services.rollback = {
-          description = "Rollback btrfs root subvolume";
-          wantedBy = [ "initrd.target" ];
-          before = [ "sysroot.mount" ];
-          after = [ "initrd-root-device.target" ];
-          unitConfig.DefaultDependencies = "no";
-          serviceConfig.Type = "oneshot";
-          script = ''
-            mkdir -p /mnt
-            DISK_LABEL="NixOS-Primary"
-            FOUND_DISK=0
-            ATTEMPTS=50
-            printf "Attempting to find disk with label '%s'\n" "$DISK_LABEL"
-            while ((ATTEMPTS > 0)); do
-              if findfs LABEL="$DISK_LABEL"; then
-                FOUND_DISK=1
-                printf "Found disk!\n"
-                break;
-              fi
-              ((ATTEMPTS--))
-              sleep .1
-              printf "Remaining disk discovery attempts: %s\n" "$ATTEMPTS"
-            done
-            if (( FOUND_DISK == 0 )); then
-              printf "Discovery of disk with label '%s' failed! Cannot rollback!\n" "$DISK_LABEL"
-              exit 1
-            fi
-
-            mount -t btrfs -o subvol=/ $(findfs LABEL="$DISK_LABEL") /mnt
-            btrfs subvolume list -to /mnt/root \
-              | awk 'NR>2 { printf $4"\n" }' \
-              | while read subvol; do
-              printf "Removing Subvolume: %s\n" "$subvol";
-              btrfs subvolume delete "/mnt/$subvol"
-            done
-
-            printf "Removing /root subvolume\n"
-            btrfs subvolume delete /mnt/root
-
-            printf "Restoring base /root subvolume\n"
-            btrfs subvolume snapshot /mnt/root-base /mnt/root
-
-            umount /mnt
-          '';
-        };
-      };
+      systemd.enable = true;
     };
   };
 }