Install a Nessus Agent on Linux

Caution: If you install a Nessus Agent on a system where an existing Nessus Agent, Nessus Manager, or Nessus scanner is running nessusd, the installation process kills all other nessusd processes. You may lose scan data as a result.

Before You Begin

  • If you previously had the Nessus Agent installed on your system, see the knowledge base article on how to avoid linking errors.

Download the Nessus Agent

On the Nessus Agents Download Page, download the package specific to your operating system.

Install Nessus Agent

Note: The following procedure requires root privileges.

Using the command line interface, install the Nessus Agent.

Example Linux Install Commands

You can install a full plugins set before linking to reduce the bandwidth impact during a mass installation. You can accomplish this by using the nessuscli agent update command with the --file parameter, which specifies the location the plugins set. You must do this before starting the Nessus Agent. For example:

/opt/nessus_agent/sbin/nessuscli agent update --file=./plugins_set.tgz

The plugins set must be less than five days old. A stale plugin set older than five days forces a full plugin download to occur. You can download a recent plugins set from the Nessus Agents download page.

Note: After installing a Nessus Agent, you must manually start the service using the command /sbin/service nessusagent start.

Link Agent Using Command Line Interface

At the command prompt, use the nessuscli agent link command. For example:

/opt/nessus_agent/sbin/nessuscli agent link

--key=00abcd00000efgh11111i0k222lmopq3333st4455u66v777777w88xy9999zabc00

--name=MyOSXAgent --groups="All" --host=yourcompany.com --port=8834

The supported arguments for this command are:

Argument Required? Value
--key

yes

Use the values you retrieved from the manager.
--host yes
--port yes

--name

no Specify a name for your agent. If you do not specify a name for your agent, the name defaults to the name of the computer where you are installing the agent.
--groups no

Specify existing agent group or groups where you want to add the agent. If you do not specify an agent group during the install process, you can add your linked agent to an agent group later in Nessus Manager or Tenable.io.

Note: The agent group name is case-sensitive and must match exactly.

--offline-install no

For Nessus Agents 7.0.3 or later, you can install the Nessus Agent on a system even if it is offline. Add the command line option offline-install="yes" to the command line input. The Nessus Agent periodically attempts to link itself to either Tenable.io or Nessus Manager.

If the agent cannot connect to the controller then it retries every hour, and if the agent can connect to the controller but the link fails then it retries every 24 hours.

--cloud no

Specify the --cloud argument to link to Tenable.io.

The --cloud argument is a shortcut to specifying --host=sensor.cloud.tenable.com --port=443 (or --host=cloud.tenable.com --port=443 for agents 8.0.x and earlier).

Note: Starting with Nessus Agent 8.1.0, Tenable.io-linked agents communicate with Tenable.io using sensor.cloud.tenable.com. If agents are unable to connect to sensor.cloud.tenable.com, they use cloud.tenable.com instead. Agents with earlier versions continue to use the cloud.tenable.com domain.
--network no For Tenable.io-linked agents, add the agent to a custom network. If you do not specify a network, the agent belongs to the default network.

If the information that you provide is incorrect, a "Failed to link agent" error appears.

Note: If you attempt to clone an agent and link it to Nessus Manager or Tenable.io, a 409 error may appear. This error appears because another machine was linked with the same UUID value in the /etc/machine_id or /etc/tenable_tag file. To resolve this issue, replace the value in the /etc/tenable_tag file with a valid UUIDv4 value. If the /etc/machine_id file does not exist, you can delete /etc/tenable_tag to generate a new value.

Note: For more information about linking agents to Tenable.io, see Link a Sensor in the Tenable.io User Guide.

Verify a Linked Agent

To verify a linked agent in Tenable.io:

  1. In the upper-left corner, click the Menu button.

    The left navigation plane appears.

  2. In the left navigation plane, click Settings.

    The Settings page appears.

  3. Click the Sensors tile.

    The Sensors page appears. By default, Nessus Scanners is selected in the left navigation menu and the Cloud Scanners tab is active.

  4. In the left navigation menu, click Nessus Agents.

    The Nessus Agents page appears and the Linked Agents tab is active.

  5. Locate the new agent in the linked agents table.

To verify a linked agent in Nessus Manager:

  1. In the top navigation bar, click Sensors.

    The Linked Agents page appears.

  2. Locate the new agent in the linked agents table.