Flash USG-3P

Unifi Security Gateway (USG-3)

Flash using console port with usb-to-serial rollover console cable and picocom

  • Download the orginal complete firmware image, version 4.2: https://dl.ubnt-ut.com/cmb/USG-4_2_0-shipped.img.bz2
  • Extract the img file from the archive.
  • Unplug the USG and remove the rubber feet from the USG.
  • Unscrew the screws beneath the rubber feet.
  • Remove the top plate to access the inside (gently pry the top off if necessary).
  • Gently remove the USB drive and insert it into your computer.
  • Use dd to write img to usb.
  • Insert the USB drive into the USG.

Connect the console cable and start minicom and power up the USG

picocom -b 115200

You will be prompted for username/password which is ubnt:ubnt

Now you need to tell the USG to update with software from a web address. Find the latest USG firmware from Unifi here or elsewhere on the Unifi site: https://www.ui.com/download/unifi-switching-routing/default/default/.

Click the download button and agree to the terms - then copy the download link e.g. https://dl.ui.com/unifi/firmware/UGW3/4.4.57.5578372/UGW3.v4.4.57.5578372.tar.

In picocom, enter: 

upgrade https://dl.ui.com/unifi/firmware/UGW3/4.4.57.5578372/UGW3.v4.4.57.5578372.tar

If don't get any response leave let the device be for 5 or 10 minutes. The USG will reboot when finished updating.

References:

  • https://www.reddit.com/r/Ubiquiti/comments/kw4bx3/how_to_flash_and_recover_unifi_security_gateway/
  • https://support.hostifi.com/en/articles/6629721-unifi-how-to-fix-a-corrupted-usg-3p