From 4143db478b4318a25c006b40019c7c2faae9e44e Mon Sep 17 00:00:00 2001
From: sajenim <its.jassy@pm.me>
Date: Sun, 14 Jan 2024 06:22:54 +0800
Subject: [PATCH] setup impermanence

---
 nixos/common/optional/ephemeral-btrfs.nix | 61 +++++++++++++++++++++++
 nixos/fuchsia/configuration.nix           |  1 +
 2 files changed, 62 insertions(+)
 create mode 100644 nixos/common/optional/ephemeral-btrfs.nix

diff --git a/nixos/common/optional/ephemeral-btrfs.nix b/nixos/common/optional/ephemeral-btrfs.nix
new file mode 100644
index 0000000..c0196cf
--- /dev/null
+++ b/nixos/common/optional/ephemeral-btrfs.nix
@@ -0,0 +1,61 @@
+{ lib, config, ... }:
+let
+  hostname = config.networking.hostName;
+in
+{
+  imports = [
+    ./persist.nix
+  ];
+
+  boot.initrd.postDeviceCommands = lib.mkAfter ''
+    mkdir /btrfs_tmp
+    mount /dev/nvme0n1p2 /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
+  '';
+
+  fileSystems = {
+    "/" = {
+      device = "/dev/disk/by-label/${hostname}";
+      fsType = "btrfs";
+      options = [ "subvol=root" "compress=zstd" ];
+    };
+
+    "/nix" = {
+      device = "/dev/disk/by-label/${hostname}";
+      fsType = "btrfs";
+      options = [ "subvol=nix" "compress=zstd" ];
+    };
+
+    "/persist" = {
+      device = "/dev/disk/by-label/${hostname}";
+      fsType = "btrfs";
+      options = [ "subvol=persist" "compress=zstd" ];
+      neededForBoot = true;
+    };
+
+    "/swap" = {
+      device = "/dev/disk/by-label/${hostname}";
+      fsType = "btrfs";
+      options = [ "subvol=swap" "compress=zstd" ];
+    };
+  };
+}
diff --git a/nixos/fuchsia/configuration.nix b/nixos/fuchsia/configuration.nix
index 83baab6..f2ab3f0 100644
--- a/nixos/fuchsia/configuration.nix
+++ b/nixos/fuchsia/configuration.nix
@@ -6,6 +6,7 @@
   imports = [
     # If you want to use modules your own flake exports (from modules/nixos):
     # outputs.nixosModules.example
+    inputs.impermanence.nixosModules.impermanence
 
     # Or modules from other flakes (such as nixos-hardware):
     # inputs.hardware.nixosModules.common-cpu-amd