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Diffstat (limited to 'nixos/doc/manual/development/etc-overlay.section.md')
| -rw-r--r-- | nixos/doc/manual/development/etc-overlay.section.md | 36 |
1 files changed, 36 insertions, 0 deletions
diff --git a/nixos/doc/manual/development/etc-overlay.section.md b/nixos/doc/manual/development/etc-overlay.section.md new file mode 100644 index 000000000000..e6f6d8d4ca1e --- /dev/null +++ b/nixos/doc/manual/development/etc-overlay.section.md @@ -0,0 +1,36 @@ +# `/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`. |