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nixpkgs/nixos/modules/misc/crashdump.nix

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Nix

{ config, lib, pkgs, ... }:
with lib;
let
crashdump = config.boot.crashDump;
kernelParams = concatStringsSep " " crashdump.kernelParams;
in
###### interface
{
options = {
boot = {
crashDump = {
enable = mkOption {
type = types.bool;
default = false;
description = ''
If enabled, NixOS will set up a kernel that will
boot on crash, and leave the user in systemd rescue
to be able to save the crashed kernel dump at
/proc/vmcore.
It also activates the NMI watchdog.
'';
};
reservedMemory = mkOption {
default = "128M";
type = types.str;
description = ''
The amount of memory reserved for the crashdump kernel.
If you choose a too high value, dmesg will mention
"crashkernel reservation failed".
'';
};
kernelParams = mkOption {
type = types.listOf types.str;
default = [ "1" "boot.shell_on_fail" ];
description = ''
Parameters that will be passed to the kernel kexec-ed on crash.
'';
};
};
};
};
###### implementation
config = mkIf crashdump.enable {
boot = {
postBootCommands = ''
echo "loading crashdump kernel...";
${pkgs.kexec-tools}/sbin/kexec -p /run/current-system/kernel \
--initrd=/run/current-system/initrd \
--reset-vga --console-vga \
--command-line="init=$(readlink -f /run/current-system/init) irqpoll maxcpus=1 reset_devices ${kernelParams}"
'';
kernelParams = [
"crashkernel=${crashdump.reservedMemory}"
"nmi_watchdog=panic"
"softlockup_panic=1"
];
kernelPatches = [ {
name = "crashdump-config";
patch = null;
extraConfig = ''
CRASH_DUMP y
DEBUG_INFO y
PROC_VMCORE y
LOCKUP_DETECTOR y
HARDLOCKUP_DETECTOR y
'';
} ];
};
};
}