On Fri, Jan 01, 2016 at 06:32:34PM +0000, Rainer Weikusat wrote:
> John Rigg <dev1@???> writes:
> > On Fri, Jan 01, 2016 at 12:26:41PM -0500, Steve Litt wrote:
> >> If / is formatted ext4, it can be mounted directly by a kernel with ext4
> >> drivers, no initramfs needed.
> >
> > Wasn't the original reason for having an initrd that the boot loader,
> > probably LILO at the time, couldn't handle a kernel image above a
> > certain size? (My recollection could be faulty here, so corrections
> > welcome).
>
> Oh wow. That got twisted :-). LILO loads a kernel image via BIOS calls
> and "10,000 years ago" (ie, I've encountered this problem once, on my
> very first Linux install, RH3.0.3, and then "nevermore" despite I've
> been using LILO all the time), the BIOS couldn't load anything beyond
> "the 1024 cylinder boundary" (504M). Hence, a kernel supposed to be
> loaded by LILO had to be located in the first 504M of a disk. This
> becomes a problem when dual-booting similarly ancient "other PC OSes"
> (in my case, OS/2 Warp 4) which insist on residing on the first primary
> partition.

The 1024 cylinder boundary was why a separate /boot partition at the start
of the disc became common, but still doesn't explain why an initrd.img
became necessary. I used to know this stuff but it was a long time ago :-)

John