Re: How does linux boot - simple
On Fri, 22 Oct 2004, Ritesh Raj Sarraf wrote:
> > BIOS does a POST, and if successful, hands off to the bootloader. The
> > bootloader loads the kernel image, then the initrd. Kernel then
> > starts running, loads modules.
initrd is optional and NOT required
modules is optional and NOT required
both depends on how the kernel was built .. with its required drivers
built into the kernel or not
> Where does it load the kernel from ?
think of booting from floppy...
- boot loader is on the floppy
- kernel is on the floppy
1st stage boot loader tells the cpu to load the 2nd stage
bootloader at a fixed address
2nd stage boot loaders loads the image located at a specific
address on the floppy into a particular address in memory
depending on bzImage or zImage
the kernel is executed after loading
> The disk, right !
lots of places that the kenrel can come from ...
dont worry about the semi messy problems of booting from scsi disks
when you insist on using scsi modules
> Suppose the disk I've got is scsi. Linux requires little arguments and add
> modules to work to boot with scsi disks in comparision to ide disks.
there is ZERO difference between booting from ide disk vs booting from
scsi disks
-- it just happens that 99% of the time, most people did NOT
turn off ide disk drivers
whereas, 99% of the time, scsi drivers are modules
which is a dumb idea
> In constrast, how does the boot-loader get the kernel image from the disk
> (scsi).
bootloader doesnt .... whatever you're booting ( cdrom, floppy, usbstick,
network-boot ) has the kernel on it ...
- ignore the confusing part about the kernel on the hardisk
think about booting from a floppy
think about booting from a cdrom
think about booting from a network
think about booting from a usbstick
dont get confused by ide disk vs scsi disks .... it's IDENTICAL
from booting issues
===
=== there is ZERO differences in booting any of the boot media
===
=== - remove the IDE modules and yuhave the same identical issue as
=== booting a scsi disk ... kernel PANIC... panic.. panic...
===
c ya
alvin
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