linux/doc/Chroot.md

Setup a Chroot Environment

A chroot environment can be used to modify a system installed to a different location.

Combined with aufs, the technique can be used, for example, to modify a mounted ISO image.

Setup

MNT=/mnt
mount -o bind /dev $MNT/dev
mount -o bind /dev/pts $MNT/dev/pts
mount -t proc none $MNT/proc
mount -t sysfs none $MNT/sys
cp /proc/mounts $MNT/etc/mtab
cp /etc/resolv.conf $MNT/etc/resolv.conf
chroot $MNT

$MNT/etc/mtab should be edited manually to correctly point to the root file system.

Umount the chroot environment:

umount $MNT/{sys,proc,dev/pts,dev}
echo > $MNT/etc/resolv.conf
rm $MNT/etc/mtab

AUFS Overlay

Mount a writeable version of /tmp/mnt/root to /tmp/mnt/rootrw

mkdir -p /tmp/mnt/{root,rootrw,aufs}
mount -t aufs -o br:/tmp/mnt/aufs:/tmp/mnt/root none /tmp/mnt/rootrw