Update the steps:


## This file /etc/opkg.conf, the overlay path is default.
option overlay_root /overlay

cp -r /usr/lib/opkg/ /tmp/mountd/disk1_part1
mv /usr/lib/opkg /usr/lib/opkgbak
ln -s /tmp/mountd/disk1_part1/opkg /usr/lib/
reboot
opkg update