I found, in Slackware, without using physical/raw partition Linux can be booted & OS will be in LVM but in general people use /boot from physical/raw partition to boot the RedHat linux System & root and other file systems would be in LVM. My doubt is how a system will be booted without using any physical partition hope this is done as lilo does not read file system
It would be appreciated for better explanation of how it is happening.
I am working on getting LVM on my notebook. The easiest way may be to use the whole disk except for a small /boot partition which needs to be outside the LVM but with an initrd compiled with LVM support :
What LVM does is give more flexible partitions. Just think of them as logical volumes in an extended partition (the volume group). I think that is the best way to describe them. It is also possible to add extra space to them if needed, or even add partitions to make them bigger. That is how I see it. I hope I am right. If I am not I am sure someone will correct me.
What my question is how LILO boots Slackware without using any physical partition like /boot used in RHEL. Hope it writes initrd also in blocks/sectors of disk where no user will access usually I think it is a place like MBR. Also would like to know whether the same can be done if I use GRUB.
The bootloader is written to the mbr unless you specify somewhere else, eg superblock of the root partition. The initrd will be written to /boot which may be in the root partition or on a partition of it's own.
I am not too sure about grub, but it may work in a similar way. I have used grub with Gentoo, but that was a few years ago. Most of my experience is with lilo. The grub man page should be helpful. I use a separate/boot partition. I reckon it is easier this way and makes life easier. The source code for grub can be found in /extra/source/grub on the DVD. That is version 0.97. Version 1.99 of grub can be found on Slackbuilds. I am sticking with lilo as it just works. Thanks to Patrick and his team for all their hard work.
I hope this helps you and is what you are looking for.
