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nixpkgs nixos-25.11 브랜치의 nixos/doc/manual/ 디렉토리를 sparse clone으로 가져와 ~/obsidian/dev/nixos-manual/에 복사. _index.md에 구조/갱신 방법 정리. 오프라인 참조 + AI 에이전트 컨텍스트용. sandbox-tokyo 같은 NixOS 노드 운영 시 빠른 참조로 사용.
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/etc via overlay filesystem
::: {.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:
{ system.etc.overlay.enable = true; }
Using an overlay has two benefits:
- it removes a dependency on perl
- 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:
{ 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.