How to chroot Ubuntu+1?
In order to chroot to do things like.. configure/install grub, do the following-
#first, mount new install to /mnt/oneiric
mount -t proc proc /mnt/oneiric/proc
mount -t sysfs sys /mnt/oneiric/sys
mount -o bind /dev /mnt/oneiric/dev
chroot /mnt/oneiric /bin/bash
I wouldn't try to start full gnome this way.
The only reason you should really be doing this is if you can't boot into the linux installation for some reason, but still need to run a few things from it. You can't just chroot over and change the distro you're running.