Once you have resolved the "already in use full" error, take these preventive measures to avoid recurrence.
Tenable commercial licenses (Nessus Professional, Tenable.io agents, Nessus Expert) often allow a limited number of fingerprint resets per year.
Changing the system hostname or network interface after generating a license file will break activation. If you must change system identity:
Resolving this error requires a methodical approach. Do not repeatedly attempt activation—this can lock the license for 24 hours. nessus offline activation license already in use full
Step 1: Identify the Exact Error Context Run the following on the scanner:
cat /opt/nessus/var/nessus/logs/nessusd.log | grep -i "license"
Look for lines containing "already in use" or "fingerprint mismatch."
Step 2: Check for Orphaned License Files
Navigate to /opt/nessus/var/nessus/ and check for license or nessus.license files. If present, back them up and delete them: Once you have resolved the "already in use
sudo mv /opt/nessus/var/nessus/nessus.license /tmp/nessus.license.bak
Step 3: Generate a Clean Challenge File Stop the Nessus service:
sudo systemctl stop nessusd
Remove the old challenge cache:
sudo rm -f /opt/nessus/var/nessus/nessus-challenge.txt
Generate a fresh challenge:
sudo /opt/nessus/sbin/nessuscli fetch --challenge
Copy this new challenge output exactly.
Step 4: Deactivate the Lost/Stale License (Critical Step) This is where most guides stop, but it is essential. You must contact Tenable Support or use the Tenable Customer Portal (if you have online access on a separate machine) to deactivate the license tied to the old system ID.
If you cannot access the portal (fully offline), you must call Tenable Support with your license activation code and the output of nessuscli fetch --challenge from the new scanner. They can manually release the lock. Changing the system hostname or network interface after
Step 5: Perform the Offline Activation Again
On an internet-connected machine, go to https://license.tenable.com/offline_activation. Upload the new challenge file. Download the resulting nessus.license file. Transfer it to the offline scanner (USB drive). Install it:
sudo /opt/nessus/sbin/nessuscli fetch --register-offline /path/to/nessus.license