sudo /opt/nessus/sbin/nessuscli fetch --challenge If the license is already active, you may see a line like: "A license is already installed" or "Offline activation failed: license already in use" .
Introduction Nessus, developed by Tenable, is one of the most widely adopted vulnerability assessment platforms in the cybersecurity industry. For organizations operating in air-gapped or highly restricted environments (e.g., government, military, financial services), the offline activation method is essential. It allows users to generate a challenge code from an isolated scanner, transfer it to an online machine to obtain a license, and then apply the license back on the offline host. nessus offline activation license already in use full
However, a notoriously frustrating error can appear during this process: (sometimes truncated as "License already in use" or "Activation limit reached" ). It allows users to generate a challenge code
sudo systemctl start nessusd This often clears the "full" state because it forces Nessus to forget any previous license handshake attempts. Once you have resolved the "already in use full" error, take these preventive measures to avoid recurrence. Best Practice #1: Always Deactivate Before Decommissioning Before retiring or reformatting a Nessus scanner, run: Once you have resolved the "already in use
"C:\Program Files\Tenable\Nessus\nessuscli.exe" fetch --challenge sudo /opt/nessus/sbin/nessuscli license --show If it shows a license but you cannot scan, you may have a corrupted or mismatched activation. Step 3: Check Tenable License Portal Status Log into your Tenable account (https://www.tenable.com). Navigate to My Account > Activation Codes . Locate your Nessus license. Below the code, it may show "Status: Activated" and the last known hostname/fingerprint. If the fingerprint does not match your current offline machine, you have found the root cause. Root Causes of the "Already in Use Full" Error Let’s break down the technical reasons why this occurs during an offline activation specifically.