This in order to provide even more security, because some of these services are crucial for the operation of the operating system. On the other hand, in systems like Unix or Linux, the services are also known as daemons. Sometimes the name of these services or daemons ends with the letter d.

Where are services defined in Linux?

The default runlevel value is defined in the initdefault line of /etc/inittab. This actually translates into a call to the /etc/init.

What a service is used for in Linux?

The service command is used to run a System V init script. Usually all system V init scripts are stored in /etc/init. d directory and service command can be used to start, stop, and restart the daemons and other services under Linux.