disko + impermanence pc

nixos/modules/impermanence/default.nix

@@ -0,0 +1,47 @@
+{ ... }:
+{
+
+    fileSystems."/persist".neededForBoot = true;
+    environment.persistence."/persist/system" = {
+    hideMounts = true;
+    directories = [
+	"/etc/nixos"
+	"/var/log"
+	"/var/lib/bluetooth"
+	"/var/lib/nixos"
+	"/var/lib/systemd/coredump"
+	"/etc/NetworkManager/system-connections"
+	{ directory = "/var/lib/colord"; user = "colord"; group = "colord"; mode = "u=rwx,g=rx,o="; }
+    ];
+    files = [
+	"/etc/machine-id"
+	{ file = "/var/keys/secret_file"; parentDirectory = { mode = "u=rwx,g=,o="; }; }
+	];
+    };
+
+    programs.fuse.userAllowOther = true;
+    boot.initrd.postDeviceCommands = lib.mkAfter ''
+    mkdir /btrfs_tmp
+    mount /dev/root_vg/root /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
+  '';
+}