From b4feb6e77ab167be38eda7e5dde8ccea78891fa5 Mon Sep 17 00:00:00 2001
From: Sam <samual.shop@proton.me>
Date: Thu, 16 May 2024 23:27:06 +0100
Subject: [PATCH] btrfs-impermanence.nix

---
 hosts/common/optional/btrfs-impermanence.nix | 26 ++++++++++++++++++++
 1 file changed, 26 insertions(+)
 create mode 100644 hosts/common/optional/btrfs-impermanence.nix

diff --git a/hosts/common/optional/btrfs-impermanence.nix b/hosts/common/optional/btrfs-impermanence.nix
new file mode 100644
index 0000000..9e7fb46
--- /dev/null
+++ b/hosts/common/optional/btrfs-impermanence.nix
@@ -0,0 +1,26 @@
+{
+boot.initrd.postDeviceCommands = lib.mkAfter ''
+    mkdir /btrfs_tmp
+    mount / /btrfs_tmp
+    if [[ -e /btrfs_tmp/root ]]; then
+        mkdir -p /btrfs_tmp/old_roots
+        timestamp=$(date --date="@$(stat -c %Y /btrfs_tmp)" "+%Y-%m-%-d_%H:%M:%S")
+        mv /btrfs_tmp "/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
+  '';
+}