How to switch to OpenWRT from Linksys

When you flash the OpenWRT the first time, the Linksys f/w switch partition on the box for you. After running OpenWRT for a while then decide to switch back to Linksys f/w, you can do so using the steps above. Now the box is running Linksys f/w. How do you switch to OpenWRT again without flashing which will wipe out everything you configured ?

This is tricky part since Linksys f/w does not have option in its Web UI that you can switch the boot/root partition, also you cannot SSH to it. Basically it is sealed. You can give the capability by performing these steps while you are login to OpenWRT.

Important: Do this before you ever switch back to Linksys firmware or you will end up flashing the OpenWRT for the second time !

    Mount the Linksys rootfs partition (as shown above) to copy OpenWRT's dropbear into it.

cp /usr/sbin/dropbear /mnt/ubi/usr/sbin

    Create script to run dropbear on Linksys f/w when you switch later on.

echo "/usr/sbin/dropbear -d /etc/dropbear_dss_host_key -r /etc/dropbear_rsa_host_key">/mnt/ubi/etc/dropbear.sh
chmod +x /mnt/ubi/etc/dropbear.sh

You can edit this file the way you like as long as you can assure that SSH will be running after you make the switch. The dropbear's keys existed in Linksys f/w. It just does not have the accompanied dropbear that uses it. Basically use the existing Linksys's own keys and enable it.

    Add to start-up list,

cd /mnt/ubi/etc/registration.d
ln -s ../init.d/dropbear.sh 99_sshd

Next time you router run its factory f/w, it will have ssh capability where you can login. The factory ssh login used to be ssh root@<your box ip>. Its password was admin. From this point onward you can safely switch between Linksys and OpenWRT firmware using boot_partxx environments. If you forgot your Linksys password you can always factory reset it !