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• guest network behaviour when controller is unreachable: link
• unifi controller should not run as root: link

HowToo

How to: Manually setting the controller address for a Unifi AP

1. SSH to ubnt:192.168.1.20 (or whatever the IP address is.) 
   default password is ubnt, if it something else, I hope you wrote it down when you set it. :)

2. You must reset the AP to defaults before changing the inform ip address. To do so execute the following command

   syswrapper.sh restore-default

   This will reboot the radio and disconnect your SSH session. Once it comes back online, you will need to reconnect.

3. Connect to the mca client

   mca-cli

   Now issue the set-inform command with the IP address of your Unifi controller.

   set-inform http://192.168.3.2:8080/inform

   The AP should connect to the controller within a few seconds and you are set.