FreeBSD 13.2 Init system

FreeBSD uses an init system called the "BSD-style init system" or "rc.d init system". It is a collection of shell scripts that are used to manage services and system startup. The init system in FreeBSD is simpler and less dynamic than some other init systems like systemd (used in many Linux distributions), but it is easy to understand, configure, and maintain.

Here's an overview of the FreeBSD init system components and how they work:

• /sbin/init: This is the first process started by the kernel during system boot. The init process sets up the basic environment, mounts necessary filesystems, and starts the main startup script, /etc/rc.

• /etc/rc: This is the main startup script that manages the boot process. It initializes system variables, sets the system hostname, configures network interfaces, and starts various services. The script reads its configuration from /etc/rc.conf and /etc/rc.conf.local (if it exists).

• /etc/rc.conf: This is the main configuration file for the FreeBSD init system. It contains global settings and service-specific settings that determine which services will start at boot and their respective configurations. You can also create a /etc/rc.conf.local file for custom settings that won't be overridden by updates.

• /etc/rc.d: This directory contains system startup scripts (also known as init scripts) for various services and system components. Each script is responsible for starting, stopping, and managing a specific service.

• /usr/local/etc/rc.d: This directory contains startup scripts for third-party applications installed via the ports or packages system. The init system will execute these scripts in addition to the ones in /etc/rc.d.

When FreeBSD boots, the init process starts the /etc/rc script, which in turn reads the configuration from /etc/rc.conf and /etc/rc.conf.local. The script then proceeds to run the startup scripts in /etc/rc.d and /usr/local/etc/rc.d in alphabetical order. Each script is responsible for starting a specific service based on the settings defined in the configuration files.

To manage services in FreeBSD, you can use the service command followed by the service name and action:

service servicename action

For example, to start, stop, or restart the SSH service, you would use:

service sshd start

service sshd stop

service sshd restart

In summary, the FreeBSD init system is a straightforward collection of shell scripts that control system startup and services management. It relies on configuration files like /etc/rc.conf and startup script directories like /etc/rc.d and /usr/local/etc/rc.d to manage services and their settings.