# systemd-sysctl.service systemd systemd-sysctl.service 8 systemd-sysctl.service systemd-sysctl Configure kernel parameters at boot /usr/lib/systemd/systemd-sysctl OPTIONS CONFIGFILE `systemd-sysctl.service` # Description `systemd-sysctl.service` is an early boot service that configures `sysctl(8)` kernel parameters by invoking `/usr/lib/systemd/systemd-sysctl`. When invoked with no arguments, `/usr/lib/systemd/systemd-sysctl` applies all directives from configuration files listed in `sysctl.d(5)`. When invoked with positional arguments, the configuration specified by the command line arguments is executed. If the string `-` is specified instead of a filename, the configuration is read from standard input. If the argument is a file name (without any slashes), all configuration directories are searched for a matching file and the file found that has the highest priority is executed. If the argument is a path, that file is used directly without searching the configuration directories for any other matching file. In addition, `--prefix=` option may be used to limit which sysctl settings are applied. See `sysctl.d(5)` for information about the configuration of sysctl settings. After sysctl configuration is changed on disk, it must be written to the files in `/proc/sys/` before it takes effect. It is possible to update specific settings, or simply to reload all configuration, see Examples below. # Options `--prefix=` Only apply rules with the specified prefix. `--strict` Always return non-zero exit code on failure (including invalid sysctl variable name and insufficient permissions), unless the sysctl variable name is prefixed with a "-" character. `--verify` After `systemd-sysctl` successfully writes a value to a sysctl variable, the variable is read back and verified to match the value that was written. If the variable cannot be read back, or if the returned value differs from the written value, the write operation is considered to have failed. To detect such failures reliably, it is recommended to also specify `--strict`, and to ensure that the settings being applied are not prefixed with `-` (see `sysctl.d(5)` for details). This mode is disabled by default, since the format accepted by the kernel may differ from the format returned when the variable is read back, or the kernel may normalize the input. As a result, verification may not work reliably in all cases. Therefore, this option is best used together with explicitly specified configuration files or settings provided through `--inline`, or with `--prefix=` to restrict the set of sysctl variables being written. `--inline` Treat each positional argument as a separate configuration line instead of a file name. When specified, at least one positional argument must be specified. `--save=FILENAME` Before applying the loaded sysctl settings, write them to `/run/sysctl.d/` using the specified filename. If the filename does not end with `.conf`, the suffix is appended. This option requires one or more positional arguments. May be combined with `--inline`. This may be useful for creating runtime sysctl configuration files or overriding existing sysctl configuration files. `--revert=FILENAME` Before loading and applying the sysctl settings, removes the specified sysctl configuration file under `/run/sysctl.d/`. If the filename does not end with `.conf`, the suffix is appended. This may be useful for removing configuration files created by `--save=`. # Credentials `systemd-sysctl` supports the service credentials logic as implemented by `ImportCredential=`/`LoadCredential=`/`SetCredential=` (see `systemd.exec(5)` for details). The following credentials are used when passed in: `sysctl.extra` The contents of this credential may contain additional lines to operate on. The credential contents should follow the same format as any other `sysctl.d/` drop-in configuration file. If this credential is passed it is processed after all of the drop-in files read from the file system. The settings configured in the credential hence take precedence over those in the file system. Note that by default the `systemd-sysctl.service` unit file is set up to inherit the `sysctl.extra` credential from the service manager. # Examples
Reset all sysctl settings
systemctl restart systemd-sysctl
View coredump handler configuration
# sysctl kernel.core_pattern kernel.core_pattern = |/usr/libexec/abrt-hook-ccpp %s %c %p %u %g %t %P %I
Update and verify coredump handler configuration
# /usr/lib/systemd/systemd-sysctl --prefix kernel.core_pattern --strict --verify This searches all the directories listed in `sysctl.d(5)` for configuration files and writes `/proc/sys/kernel/core_pattern`. The sysctl variable is read back and verified. If writing or verification fails, the command exits with a non-zero status, unless the corresponding setting is prefixed with `-`.
Update coredump handler configuration according to a specific file
# /usr/lib/systemd/systemd-sysctl 50-coredump.conf This applies all the settings found in `50-coredump.conf`. Either `/etc/sysctl.d/50-coredump.conf`, or `/run/sysctl.d/50-coredump.conf`, or `/usr/lib/sysctl.d/50-coredump.conf` will be used, in the order of preference.
Disable IPv6 on an interface and save the specified setting
# /usr/lib/systemd/systemd-sysctl --save=99-disable-ipv6-foo - <
Remove a runtime sysctl configuration file
# /usr/lib/systemd/systemd-sysctl --revert=99-disable-ipv6-foo --prefix=/net/ipv6/conf/foo This removes `/run/sysctl.d/99-disable-ipv6-foo.conf`, and applies the remaining sysctl settings for the network interface `foo`.
See `sysctl(8)` for various ways to directly apply sysctl settings. # See Also `systemd(1)`, `sysctl.d(5)`, `sysctl(8)`