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This service is essentially a random sleep() call that old software that is unable to properly handle modern hardware initialisation being asynchronous can use to *mostly* get by. Over the years is has caused so many issues in NixOS, like introducing long delays in the boot process[1], complete deadlocks[2] and even failures when reloading services or activating a new configuration[3]. systemd has been discouraging its use since 2011 (15 years ago!), then it officially deprecated it in 2018 and since 2020 it started to show on every boot a huge wall of text calling out all the offending services that still use it. Around 2021 we managed to fix around 15 NixOS modules[4] that were relying on systemd-udev-settle and practically ZFS[5] was the only remaining one. However, since then, people have actually started to bring it back with new services[6][7][8]. This is not acceptable. So, to prevent any more (lazy) uses of systemd-udev-settle, we stop providing the systemd-udev-settle.service unit entirely. For existing modules that unfortunately still need it, we replace it with the command `udevadm settle --timeout=180`, which is all that the service does. Hopefully this will also increase the awareness that it's bad and something to be fixed. Note: I tested this change using - `nixosTests.zfs`, - `nixosTests.ifstate`, - `nixosTests.misc`, - `nixosTests.openvswitch`, - `nixosTests.predictable-interface-names` - `nixosTests.nvidia-container-toolkit` and making sure that none of the 165 packages that provide upstream units (via the `systemd.packages` option) had a dependency on systemd-udev-settle.service. [1]: https://github.com/NixOS/nixpkgs/pull/25311 [2]: https://github.com/NixOS/nixpkgs/issues/107341 [3]: https://github.com/NixOS/nixpkgs/pull/113804 [4]: https://github.com/NixOS/nixpkgs/issues/73095 [5]: https://github.com/openzfs/zfs/issues/10891 [6]: https://github.com/NixOS/nixpkgs/pull/257525#discussion_r1442702970 [7]: https://github.com/NixOS/nixpkgs/pull/460075 [8]: https://github.com/NixOS/nixpkgs/pull/284507
Nixpkgs is a collection of over 120,000 software packages that can be installed with the Nix package manager. It also implements NixOS, a purely-functional Linux distribution.
Manuals
- NixOS Manual - how to install, configure, and maintain a purely-functional Linux distribution
- Nixpkgs Manual - contributing to Nixpkgs and using programming-language-specific Nix expressions
- Nix Package Manager Manual - how to write Nix expressions (programs), and how to use Nix command line tools
Community
- Discourse Forum
- Matrix Chat
- Official wiki
- Community-maintained list of ways to get in touch (Discord, Telegram, IRC, etc.)
Other Project Repositories
The sources of all official Nix-related projects are in the NixOS organization on GitHub. Here are some of the main ones:
- Nix - the purely functional package manager
- NixOps - the tool to remotely deploy NixOS machines
- nixos-hardware - NixOS profiles to optimize settings for different hardware
- Nix RFCs - the formal process for making substantial changes to the community
- NixOS homepage - the NixOS.org website
- hydra - our continuous integration system
- NixOS Branding - NixOS branding
Continuous Integration and Distribution
Nixpkgs and NixOS are built and tested by our continuous integration system, Hydra.
- Continuous package builds for unstable/master
- Continuous package builds for the NixOS 25.11 release
- Tests for unstable/master
- Tests for the NixOS 25.11 release
Artifacts successfully built with Hydra are published to cache at https://cache.nixos.org/. When successful build and test criteria are met, the Nixpkgs expressions are distributed via Nix channels.
Contributing
Nixpkgs is among the most active projects on GitHub. While thousands of open issues and pull requests might seem like a lot at first, it helps to consider it in the context of the scope of the project. Nixpkgs describes how to build tens of thousands of pieces of software and implements a Linux distribution. The GitHub Insights page gives a sense of the project activity.
Community contributions are always welcome through GitHub Issues and Pull Requests.
For more information about contributing to the project, please visit the contributing page.
Donations
The infrastructure for NixOS and related projects is maintained by a nonprofit organization, the NixOS Foundation. To ensure the continuity and expansion of the NixOS infrastructure, we are looking for donations to our organization.
You can donate to the NixOS Foundation through SEPA bank transfers or by using Open Collective:
License
Nixpkgs is licensed under the MIT License.
Note
MIT license does not apply to the packages built by Nixpkgs, merely to the files in this repository (the Nix expressions, build scripts, NixOS modules, etc.). It also might not apply to patches included in Nixpkgs, which may be derivative works of the packages to which they apply. The aforementioned artifacts are all covered by the licenses of the respective packages.