refactoring for iServer and isWorkstation: part 3

hosts/io/ephermal.nix

@@ -0,0 +1,46 @@
+{ ... }:
+
+{
+  boot.initrd.systemd.services.recreate-root = {
+    description = "Rolling over and creating new filesystem root";
+    requires = [ "initrd-root-device.target" ];
+    after = [
+      "local-fs-pre.target"
+      "initrd-root-device.target"
+    ];
+    requiredBy = [ "initrd-root-fs.target" ];
+    before = [ "sysroot.mount" ];
+    unitConfig = {
+      AssertPathExists = "/etc/initrd-release";
+      DefaultDependencies = false;
+    };
+    serviceConfig = {
+      Type = "oneshot";
+      RemainAfterExit = true;
+    };
+    script = ''
+      mkdir /btrfs_tmp
+      mount /dev/disk/by-uuid/3638cea6-5503-43cc-aa4f-3d37ebedad2f /btrfs_tmp
+      if [[ -e /btrfs_tmp/@root ]]; then
+        mkdir -p /btrfs_tmp/old_roots
+        timestamp=$(date --date="@$(stat -c %Y /btrfs_tmp/@root)" "+%Y-%m-%-d_%H:%M:%S")
+        mv /btrfs_tmp/@root "/btrfs_tmp/old_roots/$timestamp"
+      fi
+
+      delete_subvolume_recursively() {
+        IFS=$'\n'
+        for i in $(btrfs subvolume list -o "$1" | cut -f 9- -d ' '); do
+          delete_subvolume_recursively "/btrfs_tmp/$i"
+        done
+        btrfs subvolume delete "$1"
+      }
+
+      for i in $(find /btrfs_tmp/old_roots/ -maxdepth 1 -mtime +30); do
+        delete_subvolume_recursively "$i"
+      done
+
+      btrfs subvolume create /btrfs_tmp/@root
+      umount /btrfs_tmp
+    '';
+  };
+}