What is Run Level?

What is diffrent between LILO and GRUP? What is diffrent?

Run level: Determines which programs start up at boot. You could boot into single-user mode, multi-user text-mode, multi-user GUI mode.

Shutdown is also a runlevel with no software running: Switching to runlevel 0 turns off all processes, thus shutting your PC down. . .

Lilo and Grub are two different ways of managing the boot loader. If you don't know which one to use, then it doen't matter and you can use either

No, i know LILO and GRUB we can use both, but i want to know

what is diffrent between LILO and GRUB if we compare?

Grub's config lives in /boot, Lilo's in /etc

Grub has a command-shell environment, Lilo doesn't

Grub updates as soon as you edit the config file, Lilo needs doing manually

Grub understands some filesystems natively, Lilo doesn't

But at the end of the day, they both give you a text-based menu that allows you to choose amongst your boot options to start Linux or any other OS

grub also gives you some sort of security. You can set up a password. The problem with lilo is that one can boot into single user mode without having the root password and can harm your system. You can be assured that this will never happen with grub.

(1) To understand run-levels, look at man init and examine the file /etc/inittab. (And /etc/rc.d directories.)

init is the first program that starts, and it runs all the time. What it does is to start all of the other programs, and to clean-up after programs that die. The "inittab" specifies the behavior of that program. The "run level" is a parameter that determines which inittab entries are to be processed. Various elegant things are thus made possible: rebooting, and shutting down, are both handled by switching runlevels.

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(2) Both grub and LILO are programs that are responsible for getting the Linux kernel into memory in the first place. Of the two, I find that grub is much more satisfactory -- largely because of its flexibility and because of the tools that it provides for your use "when things go slightly wrong."