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Vulnerability ScanningQuick reference

Nessus Setup and Plugin Reprocessing

Linux commands for registering a Nessus scanner, managing local users, forcing plugin reprocessing, and checking the service.

Updated Aug 21, 20262 min reference

Use this sequence when a Linux Nessus installation needs to be registered with an online activation code and its plugins need to be reprocessed. Run it with administrative privileges and plan for scanner downtime: stopping nessusd interrupts active scans, and plugin reprocessing can take time on a large feed.

Register the scanner

Replace YOUR-ACTIVATION-CODE with the code assigned to this Nessus instance:

/opt/nessus/sbin/nessuscli fetch --register YOUR-ACTIVATION-CODE

Online registration also downloads current engine and plugin updates. Keep the activation code out of tickets, shared logs, screenshots, and shell-history exports.

Confirm that the scanner is registered and can reach the update feed:

/opt/nessus/sbin/nessuscli fetch --check

Reprocess the plugins

Stop the service before forcing plugin reprocessing:

systemctl stop nessusd

/opt/nessus/sbin/nessus-service -R

systemctl start nessusd

The -R option forces Nessus to reprocess the installed plugins. This is a repair or troubleshooting step, not a routine requirement after every update.

After the command completes and the service has restarted, confirm that nessusd is running:

systemctl status --no-pager nessusd

If registration succeeds but plugin reprocessing fails, preserve the exact command output and review the Nessus service logs before repeating the rebuild. Repeated restarts can hide the first useful error and extend the outage.

Add the first user

On a new Nessus instance, create the first user after plugin reprocessing finishes and nessusd has started. The command prompts for the username, password, administrative role, and user rules:

/opt/nessus/sbin/nessuscli adduser

Change an existing user’s password by replacing USERNAME with the exact Nessus login. The new password is entered interactively and is not echoed to the terminal:

/opt/nessus/sbin/nessuscli chpasswd USERNAME

List the local Nessus users:

/opt/nessus/sbin/nessuscli lsuser

Display the commands available for the installed Nessus edition:

/opt/nessus/sbin/nessuscli help

User-account capabilities vary by Nessus edition. Review the prompts before confirming administrative access or scan rules; an empty rule set may permit unrestricted scanning from that account.

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