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SubjectRe: [Q] pivot_root and initrd
Date
Followup to:  <3BCDCF1D.6030202@usa.net>
By author: Eric <ebrower@usa.net>
In newsgroup: linux.dev.kernel
>
> I am mystified that the call to 'exec /sbin/init' works if you are using
> the standard (you mention "based on RedHat7.1" util-linux") /sbin/init
> proggie, and that a standard RH7.1 initscripts would not complain when
> the root filesystem is already mounted r/w.
>
> I would also guess that you are susceptible to the kernel's change_root
> call if your /sbin/init terminates. I'll have to play with the disk a bit.
>

I modify the initscripts to not try to fsck and remount the root --
its a ramfs (tmpfs in a later version) after all. If I had been
mounting a filesystem off the harddisk I would either have mounted it
readonly and left the init scripts as-is, or fscked it before
mounting.

I pass the following command line options to the kernel (this is set
up in isolinux.cfg):

append initrd=initrd.gz root=/dev/ram0 init=/linuxrc single

By specifying root=/dev/ram0 and an explicit init (which I'm calling
/linuxrc but could just as easily have called /sbin/init) I'm telling
the kernel that this is the final root, and effectively turn off most
of the initrd legacy weirdness.

If /sbin/init exits, the kernel panics, just like it would normally do
if init goes away.

-hpa
--
<hpa@transmeta.com> at work, <hpa@zytor.com> in private!
"Unix gives you enough rope to shoot yourself in the foot."
http://www.zytor.com/~hpa/puzzle.txt <amsp@zytor.com>
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