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nixos/kexec: don't clobber existing kexec-loaded kernel #60237

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merged 2 commits into from May 6, 2019
Merged

nixos/kexec: don't clobber existing kexec-loaded kernel #60237

merged 2 commits into from May 6, 2019

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lheckemann
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Motivation for this change
Things done
  • Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS)
  • 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 nix-review --run "nix-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)
  • Assured whether relevant documentation is up to date
  • Fits CONTRIBUTING.md.

nh2
nh2 approved these changes Apr 29, 2019
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This change is very welcome; I did not even know until now that systemctl kexec on NixOS had thrown away all the kernels I had manually loaded with kexec -l before!

nixos/modules/system/boot/kexec.nix Outdated
@@ -13,6 +13,9 @@
path = [ pkgs.kexectools ];
script =
''
# Don't load the current system profile if we already have a kernel loaded
[[ 1 = "$(</sys/kernel/kexec_loaded)" ]] && exit
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Not sure if that's important here, but the below uses sh style ifs using [ ] instead of bash [[ ]]; you may want to use the same.

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There are two parts to this:

  • https://mywiki.wooledge.org/BashFAQ/031 I generally prefer [[ except in contexts where the shell might not be bash (in this case it is!), because it's easier to use correctly
  • When it's a single command that's being run conditionally and it behaves correctly with set -e, I prefer && (or || as the case may be) over if because (IMHO) if results in unhelpful visual noise.

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I have no opinion about what's better, my comment was only for the case that script does not imply bash.

nixos/modules/system/boot/kexec.nix Outdated Show resolved Hide resolved
@lheckemann lheckemann merged commit 864f4f0 into NixOS:master May 6, 2019
@lheckemann lheckemann deleted the kexec-no-clobber branch May 6, 2019 20:39
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@nh2 nh2 nh2 approved these changes

@infinisil infinisil Awaiting requested review from infinisil

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