chroot

# Put this file in the arch chroot chmod +x it and call it from that directory
mount --bind /dev dev
mount -t devpts none dev/pts
mount -t proc none proc
mount -t sysfs none sys
# Only needed if you want to share the pacman pkg cache
mount --bind /var/cache/pacman/pkg var/cache/pacman/pkg
chroot . /bin/bash
umount var/cache/pacman/pkg
umount sys
umount proc
umount dev/pts
umount dev