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. The file name must end with .conf, or it will not be read. The recommended location for local system settings is /etc/sysctl.d/local.conf but as long as you follow the rules for the name of the file, anything will work. see the sysctl.conf(5) man page for details of the format.