impermanence.nix


1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40

{ lib, ... }: {
  boot.initrd.postResumeCommands = lib.mkAfter ''
    mkdir /btrfs_tmp
    mount /dev/disk/by-partlabel/disk-main-root /btrfs_tmp # CONFIRM THIS IS CORRECT FROM findmnt
    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
  '';

  environment.persistence."/nix/persist" = {
    hideMounts = true;
    directories = [
      "/var/log"
      "/var/lib/nixos"
      "/var/lib/systemd/coredump"
    ];
    files = [
      "/etc/machine-id"
      "/etc/ssh/ssh_host_ed25519_key"
      "/etc/ssh/ssh_host_ed25519_key.pub"
    ];
  };
}