Please note that this is at YOUR OWN RISK, you could brick your device when you have root access to the controller. Please do NOT install any programs when you have root access, unless you really know what you are doing. There is almost no room left on the device, so installing a program could brick your device.
1 - Start the controller in failsafe mode:
Quote from: Girhes
There are different HW versions of the TL-WR703N - on version 1.6 you have to power on the controller, wait until the led starts flashing twice a second (it takes about 4 seconds to get there), then push the reset button immediately. When the led starts to flash much faster your device is in failsafe mode. All other HW versions: power on the controller, wait 10-12 seconds until the led starts flashing, then immediately push the reset button for 1-2 seconds. Again, if the led will start blinking rapidly you are in failsafe mode.
The versioin of your device is stated on the back of the device, underneath the barcode.
2 - Telnet into the device:
On windows go to start, type 'cmd' in the search bar, and start 'cmd.exe'. In the command window you get afterwards, type 'telnet 192.168.1.1'. Make sure you use the correct IP, my device used 192.168.1.1 in failsafe mode.
There is no user/pass required in failsafe mode.
3 - Switch to the live partition:
Type 'mount_root'
Warning! You are in the live partition now, with root permissions. You could seriously fuck thing up now!
4 - Change the root password:
Type 'passwd', and enter the password you would like (twice).
5 - Enable SSH:
Type 'vim /etc/config/dropbear', this will open the SSH config file in the vim text editor. You need to change "option enable" to "on".
You can start editing the file by hitting the 'i' key. You can now insert/delete characters. After you are finished editing hit the 'esc' key to stop editing. Now hit the ':' key, and type 'wq'. This will write the file, and quit the editor. If you made mistakes while editing, and just want to quit (without writing the file), type 'q' instead of 'wq'.
6 - Reboot the device:
Just unplug the usb power, and plug it in again.
7 - Have fun!
You can now SSH into the device while it is running in normal mode. (user: root, password whatever you entered in step 4). Just be carefull not to mess things up. If you are not at least a little familiar with linux, please be very carefull.