Failsafe Mode is a method of booting a node into a minimal configuration which allows you to log in and undo a change that may have broken the node or to change a forgotten password without having an authorized ssh key in place. Since fixing a node is an advanced topic suitable only for developers, here I will just cover how to change a password.

How to use failsafe mode:

• connect your computer the the LAN port of the node
• use a static ip address of 192.168.1.2 and netmask 255.255.255.0
  (default gateway and dns are not necessary)
• apply power to the node
• just after the DMZ LED illuminates, hold the reset button until DMZ starts blinking
• at a command prompt run "telnet 192.168.1.1"
• you should now have a prompt that looks like "root@(none)$"
  • if not, you are not in safe mode and something went wrong along the way, so stop here and start over
• type "mount_root"
• type "setpasswd abc"
  • replace abc with the password you want to use
• type "exit"

Now power cycle the node and it should accept your new password.

But be warned, I have a version 2 wrt54g for which this method does not work. Currently it is the only model I am aware of which does not work. If it doesn't work, you are Simply Outta Luck unless you can get someone with an authorized ssh key to log in to the node and help you. Failing that, your last resort is to use the tftp method described in a separate article to reinstall the firmware.