. If you try to activate a new offline instance—or even re-register the same machine after a hardware change—you will likely see the "License already in use" error. Secure Air-Gapping
: Place the nessus.license file into the appropriate directory: Windows : C:\ProgramData\Tenable\Nessus\conf Linux : /opt/nessus/etc/nessus/ nessus offline activation license already in use full
for downloading the initial plugin set. Be sure to save this URL, as it is only displayed once during the registration process. Essentials Note : Nessus Essentials does support offline installation. Do you need the specific command line Be sure to save this URL, as it
: nessuscli.exe fetch --register-offline nessus.license . Linux : nessuscli fetch --register-offline nessus.license . Troubleshooting Tips Linux : nessuscli fetch --register-offline nessus
Each Nessus Professional or Expert license comes with a fixed number of (typically 1 or 2 concurrent installs per paid license, often 1 for trial keys). When you activate offline, Tenable’s system binds the license to the scanner’s system UUID (a unique hardware/OS identifier).
| Cause | Explanation | |-------|-------------| | | Reinstalling the OS or Nessus without deactivating first creates a new fingerprint, but the old one remains registered. | | VM cloning | Cloning a Nessus-enabled VM duplicates the configuration, but Tenable sees the clone as a new machine. Both original and clone try to use same license. | | Changing major OS version | Upgrading from CentOS 7 to Rocky Linux 8 changes system UUID, triggering a new activation request. | | Hardware change | Replacing a network card, motherboard, or CPU can alter the system identifier. | | Trial license expiration & reactivation | Free trials allow 1 activation only. If you previously activated offline, you cannot do it again without Tenable resetting your key. | | Manual license reuse | Trying to use a license file (.lic) generated for a different machine ID. |