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Emily 56dea6da87 nixos: switch to switch-to-configuration-ng by default 
The Rust `switch-to-configuration-ng` rewrite was carefully written
to be compatible with the original Perl script, has been checked
against NixOS VM tests, and has been available on an opt‐in basis
for testing for the 24.05 release cycle.

The next step towards replacing the Perl script entirely is to
switch it on by default so that we can get real‐world testing from
a much greater number of users. Maintaining two implementations in
parallel is becoming a burden; we are having to adjust the systemd
service activation behaviour slightly to fix a long‐standing bug,
and backporting the changes to the Perl script is an unpleasant
process. We will do it anyway to ensure that the Rust and Perl
implementations keep parity with each other throughout the 24.11
release cycle, but we think the time has come to flip the switch.

Taking this step now will give us two to three months to test this in
the wild before the 24.11 release and gain confidence that there are
no regressions. If any non‐trivial problems arise before the final
release, we will revert to the Perl implementation by default. Doing
this switch ASAP will help to disentangle any problems that might
arise from the Rust implementation from problems that arise from the
systemd service activation changes, or the upcoming switch to using
systemd in stage 1 by default.

The main concern that was raised about replacing the Perl script in the
PR that added `switch-to-configuration-ng` was that it is currently
possible to run NixOS on systems that cannot natively host a Rust
compiler. This does not apply to any platforms that have official
support from NixOS, and as far as I know we do not know of any such
systems with users that are not cross‐compiling anyway.

My understanding is that these systems are already broken by default
anyway, as `systemd.shutdownRamfs.enable` is on by default and uses
`make-initrd-ng`, which is also written in Rust. Switching the default
while keeping the Perl implementation around will give us at least
an entire release cycle to find out if there are any users that will
be affected by this and decide what to do about it if so.

There is currently one known inconsistency between
the Perl and Rust implementations, as documented in
<https://github.com/NixOS/nixpkgs/issues/312297>; the Rust
implementation has more accurate handling of failed systemd units.

We slightly adjust the semantics of `system.switch.enable{,Ng}` to
not conflict with each other, so that `system.switch.enableNg` is
on by default, but turning off `system.switch.enable` still results
in no `switch-to-configuration` implementation being used. This
won’t break the configuration of anyone who already opted in to
`system.switch.enableNg` and is probably how the option should have
worked to begin with.
2024-09-06 08:35:43 +01:00
..
doc/manual nixos: switch to switch-to-configuration-ng by default 2024-09-06 08:35:43 +01:00
lib fix build: sdimage 2024-08-28 11:32:36 +04:00
maintainers nixos/incus: add incus-only vm and container images 2024-08-10 13:23:36 -04:00
modules nixos: switch to switch-to-configuration-ng by default 2024-09-06 08:35:43 +01:00
tests unl0kr: remove tomfitzhenry@ as maintainer (#333616) 2024-09-06 12:50:55 +08:00
COPYING
default.nix
README.md Release NixOS 24.05 2024-05-31 20:17:44 +02:00
release-combined.nix nixos/release-combined: fix evaluation 2024-06-05 17:50:37 +02:00
release-small.nix nixos/release-small: stop building amazon image 2024-08-04 23:50:46 +02:00
release.nix nixos/incus: add incus-only vm and container images 2024-08-10 13:23:36 -04:00

README.md

NixOS

NixOS is a Linux distribution based on the purely functional package management system Nix. More information can be found at https://nixos.org/nixos and in the manual in doc/manual.

Testing changes

You can add new module to your NixOS configuration file (usually it’s /etc/nixos/configuration.nix). And do sudo nixos-rebuild test -I nixpkgs=<path to your local nixpkgs folder> --fast.

Commit conventions

  • Make sure you read about the commit conventions common to Nixpkgs as a whole.

  • Format the commit messages in the following way:

    nixos/(module): (init module | add setting | refactor | etc)

(Motivation for change. Link to release notes. Additional information.)

    Examples:

    • nixos/hydra: add bazBaz option

      Dual baz behavior is needed to do foo.

    • nixos/nginx: refactor config generation

      The old config generation system used impure shell scripts and could break in specific circumstances (see #1234).

Reviewing contributions

When changing the bootloader installation process, extra care must be taken. Grub installations cannot be rolled back, hence changes may break people’s installations forever. For any non-trivial change to the bootloader please file a PR asking for review, especially from @edolstra.

Module updates

Module updates are submissions changing modules in some ways. These often contains changes to the options or introduce new options.

Reviewing process:

  • Ensure that the module maintainers are notified.
    • CODEOWNERS will make GitHub notify users based on the submitted changes, but it can happen that it misses some of the package maintainers.
  • Ensure that the module tests, if any, are succeeding.
    • You may invoke OfBorg with @ofborg test <module> to build nixosTests.<module>
  • Ensure that the introduced options are correct.
    • Type should be appropriate (string related types differs in their merging capabilities, loaOf and string types are deprecated).
    • Description, default and example should be provided.
  • Ensure that option changes are backward compatible.
    • mkRenamedOptionModuleWith provides a way to make renamed option backward compatible.
    • Use lib.versionAtLeast config.system.stateVersion "24.05" on backward incompatible changes which may corrupt, change or update the state stored on existing setups.
  • Ensure that removed options are declared with mkRemovedOptionModule.
  • Ensure that changes that are not backward compatible are mentioned in release notes.
  • Ensure that documentations affected by the change is updated.

Sample template for a module update review is provided below.

##### Reviewed points

- [ ] changes are backward compatible
- [ ] removed options are declared with `mkRemovedOptionModule`
- [ ] changes that are not backward compatible are documented in release notes
- [ ] module tests succeed on ARCHITECTURE
- [ ] options types are appropriate
- [ ] options description is set
- [ ] options example is provided
- [ ] documentation affected by the changes is updated

##### Possible improvements

##### Comments

New modules

New modules submissions introduce a new module to NixOS.

Reviewing process:

  • Ensure that all file paths fit the guidelines.
  • Ensure that the module tests, if any, are succeeding.
  • Ensure that the introduced options are correct.
    • Type should be appropriate (string related types differs in their merging capabilities, loaOf and string types are deprecated).
    • Description, default and example should be provided.
  • Ensure that module meta field is present
    • Maintainers should be declared in meta.maintainers.
    • Module documentation should be declared with meta.doc.
  • Ensure that the module respect other modules functionality.
    • For example, enabling a module should not open firewall ports by default.

Sample template for a new module review is provided below.

##### Reviewed points

- [ ] module path fits the guidelines
- [ ] module tests succeed on ARCHITECTURE
- [ ] options have appropriate types
- [ ] options have default
- [ ] options have example
- [ ] options have descriptions
- [ ] No unneeded package is added to `environment.systemPackages`
- [ ] `meta.maintainers` is set
- [ ] module documentation is declared in `meta.doc`

##### Possible improvements

##### Comments