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{ config, lib, ... }:
with lib;
let
sysctlOption = mkOptionType {
name = "sysctl option value";
check = val:
let
checkType = x: isBool x || isString x || isInt x || x == null;
in
checkType val || (val._type or "" == "override" && checkType val.content);
merge = loc: defs: mergeOneOption loc (filterOverrides defs);
};
in
{
options = {
boot.kernel.sysctl = mkOption {
default = {};
example = literalExpression ''
{ "net.ipv4.tcp_syncookies" = false; "vm.swappiness" = 60; }
'';
type = types.attrsOf sysctlOption;
description = lib.mdDoc ''
Runtime parameters of the Linux kernel, as set by
{manpage}`sysctl(8)`. Note that sysctl
parameters names must be enclosed in quotes
(e.g. `"vm.swappiness"` instead of
`vm.swappiness`). The value of each
parameter may be a string, integer, boolean, or null
(signifying the option will not appear at all).
'';
};
};
config = {
environment.etc."sysctl.d/60-nixos.conf".text =
concatStrings (mapAttrsToList (n: v:
optionalString (v != null) "${n}=${if v == false then "0" else toString v}\n"
) config.boot.kernel.sysctl);
systemd.services.systemd-sysctl =
{ wantedBy = [ "multi-user.target" ];
restartTriggers = [ config.environment.etc."sysctl.d/60-nixos.conf".source ];
};
# Hide kernel pointers (e.g. in /proc/modules) for unprivileged
# users as these make it easier to exploit kernel vulnerabilities.
boot.kernel.sysctl."kernel.kptr_restrict" = mkDefault 1;
# Disable YAMA by default to allow easy debugging.
boot.kernel.sysctl."kernel.yama.ptrace_scope" = mkDefault 0;
};
}
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