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nixos/systemd: add options for hardware watchdog management #92759

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merged 1 commit into from Jul 12, 2020
Merged

nixos/systemd: add options for hardware watchdog management #92759

merged 1 commit into from Jul 12, 2020

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mdlayher
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@mdlayher mdlayher commented Jul 9, 2020

Motivation for this change

I'd like to have systemd manage a watchdog device on one of my machines without having to write the appropriate lines into extraConfig. These options should also appear during a search for "watchdog" in NixOS options, which is what prompted me to figure out how to do this manually.

Things done
  • Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS linux)
  • Built on platform(s)
    • NixOS
    • macOS
    • other Linux distributions
  • Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
  • Tested compilation of all pkgs that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review wip"
  • Tested execution of all binary files (usually in ./result/bin/)
  • Determined the impact on package closure size (by running nix path-info -S before and after)
  • Ensured that relevant documentation is up to date
  • Fits CONTRIBUTING.md.

See https://www.freedesktop.org/software/systemd/man/systemd-system.conf.html#RuntimeWatchdogSec= for a guide on the options being set here. I have a couple of questions:

  1. The options have the suffix "Sec=" but expose a more general duration instead; is the "runtimeTime" and etc suffix I've chosen appropriate or should I go with what systemd uses: "runtimeSec"?

  2. I know there are ways to type check a unit and it would probably be smart to check for a valid unit suffix on user inputs, but I'm unsure how to do so. Any pointers would be appreciated!

/cc @grahamc per our conversation in #nixos-systemd

@mdlayher mdlayher requested a review from grahamc July 9, 2020 01:47
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mdlayher commented Jul 9, 2020

@GrahamcOfBorg test systemd

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mdlayher commented Jul 9, 2020

/marvin opt-in

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marvin-mk2 bot commented Jul 9, 2020

Hi! I'm an experimental bot. My goal is to guide this PR through its stages, hopefully ending with a merge. You can read up on the usage here.

@marvin-mk2 marvin-mk2 bot added the marvin label Jul 9, 2020
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mdlayher commented Jul 9, 2020

/status needs_reviewer

@marvin-mk2 marvin-mk2 bot requested a review from fgaz July 9, 2020 01:50
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flokli commented Jul 11, 2020

Usage question:

On my thinkpad, I already see two different watchdogs:

❯ ls -la /dev|grep watchdog
crw-------   1 root root     10, 130 Jul  9 12:21 watchdog
crw-------   1 root root    245,   0 Jul  9 12:21 watchdog0

[   11.679080] iTCO_wdt: Intel TCO WatchDog Timer Driver v1.11
[   11.679213] iTCO_wdt: Found a Intel PCH TCO device (Version=4, TCOBASE=0x0400)
[   11.679329] iTCO_wdt: initialized. heartbeat=30 sec (nowayout=0)

How am I supposed to know which one is correct?

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@flokli I note the same on my PC Engines apu4d4. I can confirm /dev/watchdog (the default) works but am rather new to the Linux watchdog subsystem and don't understand the meaning of the extra device node either unfortunately.

@flokli flokli requested review from andir and arianvp July 11, 2020 21:49
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flokli commented Jul 12, 2020

hah, mystery solved: https://unix.stackexchange.com/a/401325

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flokli commented Jul 12, 2020

So /dev/watchdog and /dev/watchdog0 should both be a fine default.

@flokli flokli merged commit 94dc0c0 into NixOS:master Jul 12, 2020
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Makes sense to me, thanks for the review and merge!

@mdlayher mdlayher deleted the mdl-systemd-watchdog branch July 12, 2020 12:27
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@flokli flokli flokli approved these changes

@grahamc grahamc Awaiting requested review from grahamc

@fgaz fgaz Awaiting requested review from fgaz

@andir andir Awaiting requested review from andir

@arianvp arianvp Awaiting requested review from arianvp

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6.topic: nixos 8.has: clean-up 8.has: module (update) 10.rebuild-darwin: 0 10.rebuild-linux: 0 awaiting_reviewer marvin
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