Before entering chroot:
for x in sys proc dev dev/pts ; do mount /$x $x -o bind,ro; done; for x in run run/lock dev/shm; do mkdir -pv $x; mount tmpfs $x -t tmpfs ; done
After exiting chroot:
for x in dev/shm run/lock run; do mkdir -pv $x; umount $x ; done; for x in dev/pts dev proc sys ; do umount $x; done