In 2002, FreeBSD integrated the NetBSD rc(8) system for system initialization. The files listed in /etc/rc.d provide basic services which can be controlled with the start, stop, and restart options to service(8). For instance, sshd(8) can be restarted with the following command:

This procedure can be used to start services on a running system. Services will be started automatically at boot time as specified in rc.conf(5). For example, to enable natd(8) at system startup, add the following line to /etc/rc.conf:

If a natd_enable="NO" line is already present, change the NO to YES. The rc(8) scripts will automatically load any dependent services during the next boot, as described below.

Since the rc(8) system is primarily intended to start and stop services at system startup and shutdown time, the start, stop and restart options will only perform their action if the appropriate /etc/rc.conf variable is set. For instance, sshd restart will only work if sshd_enable is set to YES in /etc/rc.conf. To start, stop or restart a service regardless of the settings in /etc/rc.conf, these commands should be prefixed with “one”. For instance, to restart sshd(8) regardless of the current /etc/rc.conf setting, execute the following command:

To check if a service is enabled in /etc/rc.conf, run the appropriate rc(8) script with rcvar. This example checks to see if sshd(8) is enabled in /etc/rc.conf:

To determine whether or not a service is running, use status. For instance, to verify that sshd(8) is running:

In some cases, it is also possible to reload a service. This attempts to send a signal to an individual service, forcing the service to reload its configuration files. In most cases, this means sending the service a SIGHUP signal. Support for this feature is not included for every service.

The rc(8) system is used for network services and it also contributes to most of the system initialization. For instance, when the /etc/rc.d/bgfsck script is executed, it prints out the following message:

This script is used for background file system checks, which occur only during system initialization.

Many system services depend on other services to function properly. For example, yp(8) and other RPC-based services may fail to start until after the rpcbind(8) service has started. To resolve this issue, information about dependencies and other meta-data is included in the comments at the top of each startup script. The rcorder(8) program is used to parse these comments during system initialization to determine the order in which system services should be invoked to satisfy the dependencies.

The following key word must be included in all startup scripts as it is required by rc.subr(8) to “enable” the startup script:

The following key words may be included at the top of each startup script. They are not strictly necessary, but are useful as hints to rcorder(8):

By carefully setting these keywords for each startup script, an administrator has a fine-grained level of control of the startup order of the scripts, without the need for “runlevels” used by some UNIX® operating systems.

Additional information can be found in rc(8) and rc.subr(8). Refer to this article for instructions on how to create custom rc(8) scripts.