nixos/modules/base/impermanence.nix

64 lines
2.1 KiB
Nix

{impermanence, ...}: {
# Impermanence in NixOS is where the root directory isn't permanent, but gets
# wiped every reboot (such as by mounting it as tmpfs). Such a setup is
# possible because NixOS only needs /boot and /nix in order to boot, all
# other system files are simply links to files in /nix.
# The impermanence module bind-mounts persistent files and directories,
# stored in /nix/persist, into the tmpfs root partition on startup. For
# example: /nix/persist/etc/machine-id is mounted to /etc/machine-id.
# https://github.com/nix-community/impermanence
# https://nixos.wiki/wiki/Impermanence
# https://elis.nu/blog/2020/05/nixos-tmpfs-as-root/
imports = [
impermanence.nixosModules.impermanence
];
# Each module will configure the paths they need persisted. Here we define
# some general system paths that don't really fit anywhere else.
environment.persistence."/nix/persist" = {
hideMounts = true;
directories = [
# The uid and gid maps for entities without a static id is saved in
# /var/lib/nixos. Persist to ensure they aren't changed between reboots.
{
directory = "/var/lib/nixos";
user = "root";
group = "root";
mode = "0755";
}
# Save the last run time of persistent timers so systemd knows if they were missed
{
directory = "/var/lib/systemd/timers";
user = "root";
group = "root";
mode = "0755";
}
{
directory = "/var/log";
user = "root";
group = "root";
mode = "0755";
}
# /var/tmp is meant for temporary files that are preserved across
# reboots. Some programs might store files too big for in-memory /tmp
# there. Files older than 10 days are cleaned by systemd.
{
directory = "/var/tmp";
user = "root";
group = "root";
mode = "1777";
}
];
files = [
"/etc/machine-id" # needed for /var/log
];
users.caspervk = {
directories = [
"/" # entire home directory (TODO?)
];
};
};
}