systemd Developer Lennart Poettering lennart@poettering.net sysctl.d 5 sysctl.d Configure kernel parameters at boot /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf At boot, systemd-sysctl.service8 reads configuration files from the above directories to configure sysctl8 kernel parameters. The configuration files contain a list of variable assignments, separated by newlines. Empty lines and lines whose first non-whitespace character is # or ; are ignored. Note that both / and . are accepted as label separators within sysctl variable names. kernel.domainname=foo and kernel/domainname=foo hence are entirely equivalent. Each configuration file shall be named in the style of program.conf. Files in /etc/ override files with the same name in /usr/lib/ and /run/. Files in /run/ override files with the same name in /usr/lib/. Packages should install their configuration files in /usr/lib/. Files in /etc/ are reserved for the local administrator, who may use this logic to override the configuration files installed by vendor packages. All configuration files are sorted by their filename in alphabetical order, regardless in which of the directories they reside, to guarantee that a specific configuration file takes precedence over another file with an alphabetically earlier name, if both files contain the same variable setting. If the administrator wants to disable a configuration file supplied by the vendor the recommended way is to place a symlink to /dev/null in /etc/sysctl.d/ bearing the same filename. The settings configured with sysctl.d files will be applied early on boot. The network interface-specific options will also be applied individually for each network interface as it shows up in the system. (More specifically, that is net.ipv4.conf.*, net.ipv6.conf.*, net.ipv4.neigh.* and net.ipv6.neigh.*) # Set kernel YP domain name kernel.domainname=example.com systemd1, systemd-sysctl.service8, systemd-delta1, sysctl8, sysctl.conf5