Answer: T he boot messages we can use dmesg, a command that prints on the screen the kernel ring buffer messages; the command is to be used just after the boot sequence.
The syntax of a ring buffer is like this:
dmesg
[options]. If dmesg is called with no options the messages from the
kernel will be written to the standard output.
Q. What are the differences between GRUB and LILO?
Answer : LILO (LInux LOader)
LILO stores information about the location of the kernel or other operating system on the Master Boot Record (MBR).
GNU GRUB (GRand Unified Boot loader)
GRUB has a more powerful, interactive command line interface
RUB will default to its command line interface where the user can boot the system manually.
GRUB may have difficulties booting certain hardware.
LILO and GRUB do have a number of differences:
* LILO has no interactive command interface, whereas GRUB does.
* LILO does not support booting from a network, whereas GRUB does.
* LILO stores information regarding the location of the operating systems it can to load physically on the MBR. If you change your LILO config file, you have to rewrite the LILO stage one boot loader to the MBR. Compared with GRUB, this is a much more risky option since a misconfigured MBR could leave the system unbootable. With GRUB, if the configuration file is configured incorrectly, it will simply default to the GRUB command-line interface.
http://linuxdevcenter.com/pub/a/linux/2008/01/22/lilo-and-grub-boot-loaders-made-simple.html
http://blog.webhosting.uk.com/web-hosting/what-is-difference-between-grub-and-lilo
Q. What is Kernel? Explain the task it performs.
Answer: Kernel is used in UNIX like systems and is considered to be the heart of the operating system. It is responsible for communication between hardware and software components. It is primarily used for managing the systems resources as well.
Kernel Activities:
The Kernel task manager allows tasks to run concurrently.
Managing the computer resources: Kernel allows the other programs to run and use the resources. Resources include i/o devices, CPU, memory.
Kernel is responsible for Process management. It allows multiple processes to run simultaneously allowing user to multitask.
Kernel has an access to the systems memory and allows the processes to access the memory when required.
Processes may also need to access the devices attached to the system. Kernel assists the processes in doing so.
For the processes to access and make use of these services, system calls are used.
Ref: http://www.careerride.com/Linux-Kernel.aspx
Q. Explain Boot sequence
Answer:
a) BIOS Initialization
b ) Boot Loader
c) Kernel Initialization
d) init starts and enters desired run level by executing
- /etc/rc.d/rc.sysinit
- /etc/rc.d/rc and /etc/rc.d/rcX.d/ ( X is a runlevel 0-6)
- /etc/rc.d/rc.local
- X Display manager if appropriate
Q. What are the Minimum Specifications for booting a Linux OS?
a) Label
b) Kernel Location
c) OS root File system
d) Location of the initial ram disk ( initrd)
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