Nix flake configuration for my various machines (clients and homelab servers)
fix eval error for initrd => systemd service
Parthiv Krishna
(Apr 26, 2026, 10:55 PM UTC)
54550b00
da3e1319
+43
-24
+4
-1
hosts/icicle/default.nix
+4
-1
hosts/icicle/default.nix
+39
-23
modules/features/meta/impermanence.nix
+39
-23
modules/features/meta/impermanence.nix
···
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description = "Path to root partition (will be wiped on boot)";
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};
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+
encryptedDevice = lib.mkOption {
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type = lib.types.bool;
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default = false;
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description = "Whether the root partition is on an encrypted device. If true, wipe-root will wait for cryptsetup.target.";
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};
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+
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# Home persistence options
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directories = lib.mkOption {
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type = lib.types.listOf lib.types.str;
···
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cfg:
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{ lib, ... }:
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{
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-
# startup script from https://github.com/nix-community/impermanence
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# systemd service for impermanence root wipe from https://github.com/nix-community/impermanence
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# runs in initrd to:
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# 1. backup current state of root
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# 2. clear out backups older than 30d
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# 3. make a new empty root
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boot.initrd.postDeviceCommands = lib.mkAfter ''
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mkdir /btrfs_tmp
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mount ${cfg.rootPartitionPath} /btrfs_tmp
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if [[ -e /btrfs_tmp/root ]]; then
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mkdir -p /btrfs_tmp/old_roots
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timestamp=$(date --date="@$(stat -c %Y /btrfs_tmp/root)" "+%Y-%m-%-d_%H:%M:%S")
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mv /btrfs_tmp/root "/btrfs_tmp/old_roots/$timestamp"
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fi
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# 3. make a new empty root subvolume
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boot.initrd.systemd.services.wipe-root = {
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description = "Wipe BTRFS root subvolume for impermanence";
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wantedBy = [ "initrd.target" ];
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after = lib.optionals cfg.encryptedDevice [ "cryptsetup.target" ];
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before = [ "sysroot.mount" ];
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unitConfig.DefaultDependencies = "no";
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serviceConfig.Type = "oneshot";
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script = ''
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mkdir -p /btrfs_tmp
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mount ${cfg.rootPartitionPath} /btrfs_tmp
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delete_subvolume_recursively() {
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IFS=$'\n'
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for i in $(btrfs subvolume list -o "$1" | cut -f 9- -d ' '); do
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delete_subvolume_recursively "/btrfs_tmp/$i"
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done
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btrfs subvolume delete "$1"
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-
}
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if [[ -e /btrfs_tmp/root ]]; then
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mkdir -p /btrfs_tmp/old_roots
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timestamp=$(date --date="@$(stat -c %Y /btrfs_tmp/root)" "+%Y-%m-%-d_%H:%M:%S")
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mv /btrfs_tmp/root "/btrfs_tmp/old_roots/$timestamp"
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fi
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+
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delete_subvolume_recursively() {
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IFS=$'\n'
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for i in $(btrfs subvolume list -o "$1" | cut -f 9- -d ' '); do
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delete_subvolume_recursively "/btrfs_tmp/$i"
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done
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btrfs subvolume delete "$1"
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}
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-
for i in $(find /btrfs_tmp/old_roots/ -maxdepth 1 -mtime +30); do
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delete_subvolume_recursively "$i"
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done
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for i in $(find /btrfs_tmp/old_roots/ -maxdepth 1 -mtime +30); do
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delete_subvolume_recursively "$i"
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done
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btrfs subvolume create /btrfs_tmp/root
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umount /btrfs_tmp
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'';
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btrfs subvolume create /btrfs_tmp/root
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umount /btrfs_tmp
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'';
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};
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# make sure /persist is available during boot
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fileSystems."/persist".neededForBoot = lib.mkForce true;