nixos/{networkd,dhcpcd}: remove udev-settle hack #107382

rnhmjoj · 2020-12-22T10:03:58Z

Motivation for this change

systemd-udev-settle is a terrible hack1 and should never2 ever3
used, seriously it's very bad. It was used as a stop-gap solution for
issue #39069, but thanks to PR #79532 it can be removed now.

Things done

Tested via:
- nixosTests.networking.networkd
- nixosTests.networking.scripted
- nixosTests.predictable-interface-names
Ensured that relevant documentation is up to date
Fits CONTRIBUTING.md.

nixos-discourse · 2020-12-22T10:06:59Z

This pull request has been mentioned on NixOS Discourse. There might be relevant details there:

https://discourse.nixos.org/t/boot-faster-by-disabling-udev-settle-and-nm-wait-online/6339/4

flokli · 2020-12-22T10:17:08Z

Shower thought: Do we copy and apply all udev rules into initrd?

I'm a bit worried about 70-persistent-net.rules-style udev rules not getting applied before dhcpcd starts doing its thing. Such a rule is mentioned as an example in nixos/modules/services/hardware/udev.nix for services.udev.extraRules

The systemd-udev-settle.service might be what's preventing this from happening for now.

We should add a test for this, to ensure it keeps working.

peterhoeg · 2020-12-22T12:29:52Z

There is some additional information here: #25311

rnhmjoj · 2021-01-07T19:54:44Z

flokli · 2021-01-09T00:45:41Z

@rnhmjoj can you add a test for the services.udev.extraRules rename example into nixos/tests/networking.nix? I assume you could just add another interface (via the vlan argument), and ensure it gets renamed via the udev rule.

rnhmjoj · 2021-01-09T13:38:02Z

@flokli Thank you for the suggestion: there is indeed a problem here. I wrote this small test:

 {
   rename = {
      name = "RenameInterface";
      machine = { pkgs, ... }: {
        virtualisation.vlans = [ 1 ];
        networking = {
          useNetworkd = networkd;
          useDHCP = false;
        };
        services.udev.extraRules = ''
          SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="52:54:00:12:01:01", KERNEL=="eth*", NAME="custom_name"
        '';
      };
      testScript = ''
        machine.succeed("udevadm settle")
        print(machine.succeed("ip link show dev custom_name"))
      '';
    };
}

The "scripted" variant works, but the renaming fails when netword is enabled:

systemd-udevd[481]: eth1: Failed to rename network interface 3 from 'eth1' to 'custom_name': Device or resource busy

I'm not sure what this means...

flokli · 2021-01-10T22:28:45Z

The linked #79532 kinda does something similar this:

We copy ${udev}/lib/systemd/network/*.link into the initrd, and also some udev rules related to interface renaming, so the renaming happens early, before interfaces are up (and we don't race with networkd or scripted networking also configuring interfaces).

I feel like we need to copy more of the .link files into initrd, and the udev extraRules as well. cc-ing @fpletz, @Ma27, @emilazy and @mweinelt from #79532 for opinions.

nixos-discourse · 2021-02-18T10:30:47Z

This pull request has been mentioned on NixOS Discourse. There might be relevant details there:

https://discourse.nixos.org/t/prs-in-distress/3604/39

systemd-udev-settle is a terrible hack[1] and should never[2] ever[3] used, seriously it's very bad. It was used as a stop-gap solution for issue NixOS#39069, but thanks to PR NixOS#79532 it can be removed now. [1]: systemd/systemd#7293 (comment) [2]: NixOS#73095 [3]: NixOS#107341

Renaming an interface must be done in stage-1: otherwise udev will report the interface as ready and network daemons (networkd, dhcpcd, etc.) will bring it up. Once up the interface can't be changed and the renaming will fail. Note: link files are read directly by udev, so they can be used even without networkd enabled.

nixos/doc/manual/configuration/renaming-interfaces.xml

nixos/doc/manual/release-notes/rl-2105.xml

nixos/modules/services/hardware/udev.nix

Note: this moves the example rule used to rename network interfaces in the new udev.initrdRules option, which is required since 115cdd1c.

erictapen · 2021-02-21T11:45:34Z

@rnhmjoj I'm using this for a while now ontop of nixos-20.09. What do you think about backporting this?

Edit: Nevermind, I just read the addition to the release notes. Doesn't sound safe to backport.

rnhmjoj · 2021-02-21T12:52:25Z

@erictapen Yes, unfortunately it can't be easily backported.
If you're not using gdm or zfs, it should be mostly safe to do systemd-udev-settle.enable = false and disable udev-settle entirely.

arianvp · 2021-04-04T16:36:58Z

nixos/modules/services/hardware/udev.nix

@@ -202,12 +202,26 @@ in
        '';
      };

-      extraRules = mkOption {
+      initrdRules = mkOption {


Hmmph not particularily fond of having this option defined here. This module is for configuring systemd-udevd in stage 2; not stage 1

how about instead of having an initrdRules here; we move this option to stage-1.nix and name it boot.initrd.extraUdevRules ? It's a bit weird to have the the option for initrd defined here as udevd in initrd and udevd in stage-2 might be two completely different udevd implementations at this moment.

I'm working on an alternative initrd implementation using systemd. But it's hard to introduce this change as now the udev module in stage-2 has a hard dependency on the stage-1.nix module. Because now the stage-2 udev module calls out to stage-1.nix I can not disable stage-1.nix in disabledModules

I'll send a draft PR with these suggested changes and i'll backlink it here.

I think renaming this option is fine - as long as we do this before the 20.05 branchoff, it probably doesn't even need the mkRenamedOption alias.

rnhmjoj requested review from fpletz, flokli, srhb and xeji December 22, 2020 10:03

flokli mentioned this pull request Dec 22, 2020

nixos/udev: harmonize extraRules example #107385

Merged

10 tasks

rnhmjoj force-pushed the no-udev-settle branch from b331ba7 to 1ebe140 Compare February 18, 2021 21:03

rnhmjoj added 2 commits February 18, 2021 22:07

rnhmjoj force-pushed the no-udev-settle branch from 1ebe140 to 4459cb4 Compare February 18, 2021 21:07

ofborg bot added 8.has: changelog 8.has: documentation This PR adds or changes documentation labels Feb 18, 2021

flokli reviewed Feb 18, 2021

View reviewed changes

rnhmjoj force-pushed the no-udev-settle branch 3 times, most recently from b85dce1 to 9d34123 Compare February 19, 2021 00:02

rnhmjoj added 3 commits February 19, 2021 09:26

nixos/udev: add option to install rules in initrd

8e59a68

Note: this moves the example rule used to rename network interfaces in the new udev.initrdRules option, which is required since 115cdd1c.

nixos/tests/networking: test interface renaming

7384c81

nixos/docs: add section on renaming interfaces

aafaf3b

nixos/release-notes: warn on interface renaming

d683d26

rnhmjoj force-pushed the no-udev-settle branch from 9d34123 to d683d26 Compare February 19, 2021 08:26

rnhmjoj merged commit 19d715c into NixOS:master Feb 20, 2021

arianvp reviewed Apr 4, 2021

View reviewed changes

knuton mentioned this pull request Jun 16, 2021

[20.09] 3-minute delay at boot waiting for wpa_supplicant to restart; may also result in failure to configure the wireless interface #107341

Closed

rnhmjoj deleted the no-udev-settle branch July 10, 2023 13:56

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nixos/{networkd,dhcpcd}: remove udev-settle hack #107382

nixos/{networkd,dhcpcd}: remove udev-settle hack #107382

rnhmjoj commented Dec 22, 2020 •

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nixos-discourse commented Dec 22, 2020

flokli commented Dec 22, 2020

peterhoeg commented Dec 22, 2020

rnhmjoj commented Jan 7, 2021 •

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flokli commented Jan 9, 2021

rnhmjoj commented Jan 9, 2021

flokli commented Jan 10, 2021

nixos-discourse commented Feb 18, 2021

erictapen commented Feb 21, 2021 •

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rnhmjoj commented Feb 21, 2021

arianvp Apr 4, 2021

arianvp Apr 4, 2021

flokli Apr 4, 2021

nixos/{networkd,dhcpcd}: remove udev-settle hack #107382

nixos/{networkd,dhcpcd}: remove udev-settle hack #107382

Conversation

rnhmjoj commented Dec 22, 2020 • edited Loading

Motivation for this change

Things done

nixos-discourse commented Dec 22, 2020

flokli commented Dec 22, 2020

peterhoeg commented Dec 22, 2020

rnhmjoj commented Jan 7, 2021 • edited Loading

flokli commented Jan 9, 2021

rnhmjoj commented Jan 9, 2021

flokli commented Jan 10, 2021

nixos-discourse commented Feb 18, 2021

erictapen commented Feb 21, 2021 • edited Loading

rnhmjoj commented Feb 21, 2021

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rnhmjoj commented Dec 22, 2020 •

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rnhmjoj commented Jan 7, 2021 •

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erictapen commented Feb 21, 2021 •

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