I'm looking for a tutorial that explains how to install a *.nas firmware (such as ASUS's original or Kfurge's custom version) when the web-interface is not working (any more) and when you don't have a Windows machine on which to run ASUS's firmware update tool.

Although the web-interface doesn't come up, I can get the machine into the state where it waits for a *.trx firmware via TFTP, but I don't know how to extract the *.trx file from the *.nas bundle and neither do I know how to transfer the rest of the *.nas file afterwards.