Merge pull request #270727 from nikstur/nixos-perlless-activation

profiles/hardened.section.md

profiles/headless.section.md

profiles/installation-device.section.md

profiles/perlless.section.md

profiles/minimal.section.md

profiles/qemu-guest.section.md

```

# Perlless {#sec-perlless}

::: {.warning}

If you enable this profile, you will NOT be able to switch to a new

configuration and thus you will not be able to rebuild your system with

nixos-rebuild!

:::

Render your system completely perlless (i.e. without the perl interpreter). This

includes a mechanism so that your build fails if it contains a Nix store path

that references the string "perl".

The flag `-r` deletes the user's home directory. Accounts can be

modified using `usermod`. Unix groups can be managed using `groupadd`,

`groupmod` and `groupdel`.

## Create users and groups with `systemd-sysusers` {#sec-systemd-sysusers}

::: {.note}

This is experimental.

:::

Instead of using a custom perl script to create users and groups, you can use

systemd-sysusers:

```nix

systemd.sysusers.enable = true;

```

The primary benefit of this is to remove a dependency on perl.

# `/etc` via overlay filesystem {#sec-etc-overlay}

::: {.note}

This is experimental and requires a kernel version >= 6.6 because it uses

new overlay features and relies on the new mount API.

:::

Instead of using a custom perl script to activate `/etc`, you activate it via an

overlay filesystem:

```nix

system.etc.overlay.enable = true;

```

Using an overlay has two benefits:

1. it removes a dependency on perl

2. it makes activation faster (up to a few seconds)

By default, the `/etc` overlay is mounted writable (i.e. there is a writable

upper layer). However, you can also mount `/etc` immutably (i.e. read-only) by

setting:

```nix

system.etc.overlay.mutable = false;

```

The overlay is atomically replaced during system switch. However, files that

have been modified will NOT be overwritten. This is the biggest change compared

to the perl-based system.

If you manually make changes to `/etc` on your system and then switch to a new

configuration where `system.etc.overlay.mutable = false;`, you will not be able

to see the previously made changes in `/etc` anymore. However the changes are

not completely gone, they are still in the upperdir of the previous overlay in

`/.rw-etc/upper`.

unit-handling.section.md

activation-script.section.md

non-switchable-systems.section.md

etc-overlay.section.md

```