pyrox.dev
1# `/etc` via overlay filesystem {#sec-etc-overlay}
2
3::: {.note}
4This is experimental and requires a kernel version >= 6.6 because it uses
5new overlay features and relies on the new mount API.
6:::
7
8Instead of using a custom perl script to activate `/etc`, you activate it via an
9overlay filesystem:
10
11```nix
12{
13 system.etc.overlay.enable = true;
14}
15```
16
17Using an overlay has two benefits:
18
191. it removes a dependency on perl
202. it makes activation faster (up to a few seconds)
21
22By default, the `/etc` overlay is mounted writable (i.e. there is a writable
23upper layer). However, you can also mount `/etc` immutably (i.e. read-only) by
24setting:
25
26```nix
27{
28 system.etc.overlay.mutable = false;
29}
30```
31
32The overlay is atomically replaced during system switch. However, files that
33have been modified will NOT be overwritten. This is the biggest change compared
34to the perl-based system.
35
36If you manually make changes to `/etc` on your system and then switch to a new
37configuration where `system.etc.overlay.mutable = false;`, you will not be able
38to see the previously made changes in `/etc` anymore. However the changes are
39not completely gone, they are still in the upperdir of the previous overlay in
40`/.rw-etc/upper`.