What is Linux init process?

init is parent of all Linux processes with PID or process ID of 1. It is the first process to start when a computer boots up and runs until the system shuts down. init stands for initialization.

What is the init process in Linux?

Init is the parent of all processes, executed by the kernel during the booting of a system. Its principle role is to create processes from a script stored in the file /etc/inittab. It usually has entries which cause init to spawn gettys on each line that users can log in.

How many runlevels are available in Linux?

seven runlevels
A runlevel is a mode of operation in the computer operating systems that implements Unix System V-style initialization. Conventionally, seven runlevels exist, numbered from zero to six.

What is Linux init?

How do I change runlevels in Linux?

You can change the runlevels using the command telinit (stands for telling init o change runlevel). This actually signals “init” process to change runlevel.

What does init 6 do in Linux?

These are generally defined as: The init command tells the system to move to the specified runlevel. Because 6 is the commonly defined runlevel used to reboot the host, and init 6 (or telinit 6) is the means to go to that runlevel, this is why init 6 is generally understood to be a reboot command.

What is the difference between reboot and init 6?

Internally they do exactly the same thing: reboot uses the shutdown command (with the -r switch). init 6 tells the init process to shutdown all of the spawned processes/daemons as written in the init files (in the inverse order they started) and lastly invoke the shutdown -r now command to reboot the machine

What is the use of inittab in Linux?

It runs as a daemon and typically has PID 1. It is the parent of all processes. Its primary role is to create processes from a script stored in the file /etc/inittab file. The main advantages is flexibility and scalability provided by SysV.

Why don’t all Unix variants use the same runlevels for init?

This is because “traditional” Unix variants don’t use them. In case you’re curious, runlevels S and s are in fact the same. Internally they are aliases for the same runlevel. After init is invoked as the last step of the kernel boot sequence, it looks for the file /etc/inittab to see if there is an entry of the type initdefault (see inittab (5)).