commit dbd8cb9d460aefddce0afd09ffdce5271a6f36bd · pyrox.dev/nixpkgs

+36

nixos/doc/manual/development/etc-overlay.section.md

···

       1
       1
       +
       # `/etc` via overlay filesystem {#sec-etc-overlay}

     

       2
       2
       +
       

     

       3
       3
       +
       ::: {.note}

     

       4
       4
       +
       This is experimental and requires a kernel version >= 6.6 because it uses

     

       5
       5
       +
       new overlay features and relies on the new mount API.

     

       6
       6
       +
       :::

     

       7
       7
       +
       

     

       8
       8
       +
       Instead of using a custom perl script to activate `/etc`, you activate it via an

     

       9
       9
       +
       overlay filesystem:

     

       10
       10
       +
       

     

       11
       11
       +
       ```nix

     

       12
       12
       +
       system.etc.overlay.enable = true;

     

       13
       13
       +
       ```

     

       14
       14
       +
       

     

       15
       15
       +
       Using an overlay has two benefits:

     

       16
       16
       +
       

     

       17
       17
       +
       1. it removes a dependency on perl

     

       18
       18
       +
       2. it makes activation faster (up to a few seconds)

     

       19
       19
       +
       

     

       20
       20
       +
       By default, the `/etc` overlay is mounted writable (i.e. there is a writable

     

       21
       21
       +
       upper layer). However, you can also mount `/etc` immutably (i.e. read-only) by

     

       22
       22
       +
       setting:

     

       23
       23
       +
       

     

       24
       24
       +
       ```nix

     

       25
       25
       +
       system.etc.overlay.mutable = false;

     

       26
       26
       +
       ```

     

       27
       27
       +
       

     

       28
       28
       +
       The overlay is atomically replaced during system switch. However, files that

     

       29
       29
       +
       have been modified will NOT be overwritten. This is the biggest change compared

     

       30
       30
       +
       to the perl-based system.

     

       31
       31
       +
       

     

       32
       32
       +
       If you manually make changes to `/etc` on your system and then switch to a new

     

       33
       33
       +
       configuration where `system.etc.overlay.mutable = false;`, you will not be able

     

       34
       34
       +
       to see the previously made changes in `/etc` anymore. However the changes are

     

       35
       35
       +
       not completely gone, they are still in the upperdir of the previous overlay in

     

       36
       36
       +
       `/.rw-etc/upper`.

nixos/doc/manual/development/what-happens-during-a-system-switch.chapter.md

···

       56
       56
        
       unit-handling.section.md

     

       57
       57
        
       activation-script.section.md

     

       58
       58
        
       non-switchable-systems.section.md

     

       59
       59
       +
       etc-overlay.section.md

     

       59
       60
        
       ```