linux kernel booting
Plz. do rectify me at all the wrong points!!!
when bootloader in bios executes its code, it do POST and other things...then as I read from somewhere kernel does initrd to load some basic modules so as to mount the root file system and then removes initrd filesystem to make the space ..... 1.how does kernel do initrd as the kernel(vmlinuz) itself is present on the harddisk ....i mean how the control is transferrred to the kernel(present in hdd) from the bios???? --at initial point drivers(i mean the protocol to access the harddisk) is not known then how the MBR is accessed ?? 2.can we put the kernel (even though very small part of it) in the bios itself?? Regards,, saurabh |
Hi there,
quite a sophisticated process that you're trying to understand! The boot process is actually more complicated than you think. Your understanding is more or less correct, but incomplete.
Quote:
[X] Doc CPU |
For all it's worth (assuming you're using something that uses GRUB):
http://docs.redhat.com/docs/en-US/Re...ub-whatis.html Cheers, Tink |
thanks Tinkster and Doc CPU,,,
one more question: 1.does the meaning of bootloader is limited to any code that cause the booting of os?? 2.the bios also does a similar thing(not activating the OS,, a lot of initiallisation and other things),, is it also a (sort of)bootloader??? |
Ad 2)
The BIOS reads the first few bytes (I think 512) of the first sector of the boot device into memory, and point the execution pointer of the CPU at it. Ad 1) I don't really understand what you're saying, but: The boot loader (part of which sits in those 512 bytes above) will then try to load the kernel (or the "other OSes" equivalent), and have it carry on with execution in the same way - setting the CPUs execution pointer at the memory location into which it loaded whatever it slurped of the disk. Cheers, Tink |
So sir,
1.can i say that after the initiallisation that the bios do, the bios code can access all the peripherals completely??? 2.I mean that from the bios code only,, can i acess the harddisk completely..specifically the kernel bcz. If i have accessed the MBR!! which is in harddisk, so can i access the remaining part of it too ?? 3.if not. Then is it possible to extend the size of MBR(just asking) so as to fit the kernel in it(it will initiallise all the peripherals and other things ) thus removing the bootloadr?? |
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of BIOS' responsibility. Quote:
that's all you get to play with. And no, I don't think you can write a replacement kernel that will fit in there and do all the work. Cheers, Tink |
Hi there,
let me add a few words to what Tinkster said. Quote:
Quote:
On newer computers that support GPT partitioning, the GUID partition table can be several sectors long, starting after the traditional MBR. Quote:
[X] Doc CPU |
thanks Doc CPU and Tinkster,, for clearing some of my doubts...
Regards, |
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