Kernel system variables configuration files Files found under the /etc/sysctl.d directory that end with .conf are parsed within sysctl(8) at boot time. If you want to set kernel variables you can either edit /etc/sysctl.conf or make a new file. The filename isn't important, but don't make it a package name as it may clash with something the package builder needs later. It must end with .conf though. My personal preference would be for local system settings to go into /etc/sysctl.d/local.conf but as long as you follow the rules for the names of the file, anything will work. See sysctl.conf(8) man page for details of the format.