What is /proc/sys/kernel/real-root-device

HaroldWho · 10-14-2008, 02:54 PM

The 'proc' documentation in the kernel source doesn't mention this item. On my own box it's set to 0, and everything works OK.

However, I've seen an init script for use for an initramfs boot that contains the line "echo 0x0010 > /proc/sys/kernel/real-root-device" just before a "switch_root" command is issued.

Can anyone help me with the significance of that proc item?

HaroldWho

syg00 · 10-15-2008, 07:48 AM

Try "man proc"

HaroldWho · 10-15-2008, 01:58 PM

Well, that's *half* the story. BTW, I'd never have tried 'man proc' without your suggestion.

Now, here's my next question:

'man proc' tells me that:

If /proc is mounted, the "real" root device can be changed from within linuxrc by writing the number of the new root FS device to the special
file /proc/sys/kernel/real-root-dev, e.g.
# echo 0x301 >/proc/sys/kernel/real-root-dev

What the heck do they mean by "the number" of the new root FS?

HW