How does the boot process[init levels] work on Linux? How is it different from

How does the boot process[init levels] work on Linux? How
is it different from Solaris?

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How does the boot process[init levels] work on Linux? How is it different from Solaris? ..

Answer / sanjay

1. The system BIOS checks the system and launches the first
stage boot loader on the MBR of the primary hard disk.

2. The Frist stage boot loader loads itself into memory and
launches the second stage boot loader from the /boot/
partition.

3. The second stage boot loader loads the kernel into
memory, which in turn loads any necessary modules and
mounts the root
partition read-only.

4. The kernel transfers control of the boot process to the /
sbin/init program.

5. The /sbin/init program loads all services and user-space
tools, and mounts all partitions
listed in /etc/fstab.

6. The user is presented with a login screen for the
freshly booted Linux system.

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How does the boot process[init levels] work on Linux? How is it different from Solaris? ..

Answer / dharmesh pitroda

There?s a big difference in the way run levels work on Linux
compared to Solaris. Linux goes straight in at a run-level,
whereas Solaris works up through them (and is better for it,
IMNSHO).

inittab for configuring the run-level; symbolic links;
chkconfig for configuring a service to start; service for
starting them if you don?t fancy running scripts manually.
Perhaps some anecdotes about the actual writing of init scripts.

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1 No

How does the boot process[init levels] work on Linux? How is it different from Solaris? ..

Answer / dayashankar prajapat

When an x86 computer is booted, the processor looks at the
end of the system memory for the BIOS (Basic Input/Output
System) and runs it. The BIOS program is written into
permanent read-only memory and is always available for use.
The BIOS provides the lowest level interface to peripheral
devices and controls the first step of the boot process.

The BIOS tests the system, looks for and checks peripherals,
and then looks for a drive to use to boot the system.
Usually it checks the floppy drive (or CD-ROM drive on many
newer systems) for bootable media, if present, and then it
looks to the hard drive. The order of the drives used for
booting is usually controlled by a particular BIOS setting
on the system. Once Linux is installed on the hard drive of
a system, the BIOS looks for a Master Boot Record (MBR)
starting at the first sector on the first hard drive, loads
its contents into memory, then passes control to it.

This MBR contains instructions on how to load the GRUB (or
LILO) boot-loader, using a pre-selected operating system.
The MBR then loads the boot-loader, which takes over the
process (if the boot-loader is installed in the MBR). In the
default Red Hat Linux configuration, GRUB uses the settings
in the MBR to display boot options in a menu. Once GRUB has
received the correct instructions for the operating system
to start, either from its command line or configuration
file, it finds the necessary boot file and hands off control
of the machine to that operating system.

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6 No

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