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If you have any issues in connecting to the internet, you can choose to activate offline, as shown in the following screenshot:

In order for the Nessus to be activated offline, a challenge code is displayed on your local browser where the Nessus instance is running, or can be displayed manually by using the following commands:

• On Linux, use the following command:

# /opt/nessus/sbin/nessuscli fetch --challenge

• On FreeBSD, use the following command:

# /usr/local/nessus/sbin/nessuscli fetch --challenge

• On macOS X, use the following command:

# /Library/Nessus/run/sbin/nessuscli fetch --challenge

• On Windows, use the following command:

C:\Program Files\Tenable\Nessus>nessuscli.exe fetch --challenge

You can copy this challenge code onto a machine where the internet is available, and generate a license using the offline module on the Nessus website at https://plugins.nessus.org/v2/offline.php, and generate a license string. This license string can be used on the machine, in either the browser or offline mode, using the following commands:

• On Linux, use the following command:

# /opt/nessus/sbin/nessuscli fetch --register-offline /opt/nessus/etc/nessus/nessus.license

• On FreeBSD, use the following command:

# /usr/local/nessus/sbin/nessuscli fetch --register-offline /usr/local/nessus/etc/nessus/nessus.license

• On macOS X, use the following command:

# /Library/Nessus/run/sbin/nessuscli fetch --register-offline /Library/Nessus/run/etc/nessus/nessus.license

• On Windows, use the following command:

C:\Program Files\Tenable\Nessus>nessuscli.exe fetch --register-offline "C:\ProgramData\Tenable\Nessus\conf\nessus.license"