Clearing Ubiquiti UniFi USG DNS entries

Another post to save Future Howard the trouble of trying to remember how to fix a problem: when the DNS server in the USG-PRO has cached an old or invalid IP for a host. To verify:

  • SSH to the USG-PRO itself (not the Cloud Key/Controller).
  • To see the list of IPs it has stored, with the incorrect entry:
    cat /etc/hosts
  • To edit (elevated) and remove the offending line
    sudo vi /etc/hosts
  • And to ensure the DNS service forgets the incorrect value:
    clear dns forwarding cache

You’re welcome, Future Howard.