Do not try to upgrade over a wireless network! Seldom (if ever?) will this be successful.Instead, hook it up directly to the computer from which you will be upgrading.

You can force the NSLU2 into "upgrade mode" using the reset button at power-on. You will need to do this if you want to use the Upslug2 (Linux) or Sercomm (Windows) program to reprogram the flash. Proceed as follows:

1. Shutdown the slug
2. Using a paper clip (or pushpin), push and hold in the reset button. (The reset button is located on the back of the NSLU2 above the power connection.)
3. While holding in the reset button, press and release the power button.
4. Watch the orange Ready/Status LED and after approx 10 seconds the LED will turn solid red (except for some models, see note below). Quickly release the reset button.
5. You should be in upgrade mode which is indicated by the Ready/Status LED alternating between red and green.

If the Ready/Status LED is flashing yellow rather than red/green, you didn't release the reset button quickly enough after the Ready/Status LED turned red, and the Slug is now in "assign mode", whatever that means. Don't panic; just remove the power and start again.

Note on LED colours

Older slugs have a clearly distinguishable red status LED color. Newer ones (sometime in late 2006) are not as distinguishable. It will go from orange to a slightly darker orange. If you have trouble seeing the change, the secret is to not look directly at the led; at about 45 degrees off center the contrast change is much clearer. Adjust the lighting conditions also if necessary (darker room is probably better). The procedure to enter the upgrade mode is just the same as described above though, but you have to eye the status LED more carefully to get the right reset release moment. In my case, the timing was also closer to 7 seconds rather than 10.