# Install a Nessus Agent on Windows

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.

Note: This procedure describes deploying Nessus Agents via the command line. You can also deploy Nessus Agents with a standard Windows service such as Active Directory (AD), Systems Management Server (SMS), or other software delivery system for MSI packages. For more information on deploying via these methods, see the appropriate vendor's documentation.

Note: You may be required to restart your computer to complete installation.

Before You Begin

• Retrieve the Nessus Agents linking key.
• If you previously had the Nessus Agent installed on your system, see the knowledge base article on how to avoid linking errors.
• Consider the following if you are reinstalling Nessus Agent after uninstalling it:
• If you previously had the Nessus Agent installed on your system, see the knowledge base article on how to avoid linking errors.
• On Windows, the Nessus Agent uninstall process automatically creates a backup file in the %TEMP% directory. If you reinstall Nessus Agent within 24 hours, Nessus Agent uses that backup file to restore the installation. If you want to reinstall Nessus Agent within 24 hours without using the backup, manually delete the backup file in the %TEMP% directory beforehand.

Deploy and Link via the Command Line

You can deploy and link Nessus Agents via the command line. For example:

Note: You must have administrator-level privileges to deploy and link via the command line.

msiexec /i NessusAgent-<version number>-x64.msi NESSUS_GROUPS="Agent Group Name" NESSUS_SERVER="192.168.0.1:8834" NESSUS_KEY=00abcd00000efgh11111i0k222lmopq3333st4455u66v777777w88xy9999zabc00 /qn

The following are available linking parameters:

Parameter Description
NESSUS_OFFLINE_INSTALL You can install the Nessus Agent on a system even if it is offline. Add the command line option NESSUS_OFFLINE_INSTALL="yes" to the command line input. The Nessus Agent will periodically attempt 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.
NESSUS_SERVICE_AUTOSTART=false

Prevents the Nessus Agent from starting up after installation.

This parameter can be useful for streamlined deployment options (for example, deploying using a JSON file).

ADDLOCAL=ALL Install the Nessus Agent system tray application, as described in Configure and View the System Tray Application in the Nessus Agent Deployment and User Guide.
NESSUS_PLUGINS_FILEPATH="C:\path\to\plugins_set.tgz" Install a full plugins set before linking to reduce the bandwidth impact during a mass installation. Add the command line option NESSUS_PLUGINS_FILEPATH="C:\path\to\plugins_set.tgz" where plugins_set.tgz is a recent plugins set tarball less than five days old. A stale plugins set older than five days will force a full plugins download to occur. You can download a recent plugins set from the Tenable downloads page.
NESSUS_GROUPS

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.

Note: Quotation marks (") are necessary when listing multiple groups, or one group with spaces in its name. For example:

• GroupName
• "Group Name"
• "Group, Another Group"

NESSUS_PROCESS_PRIORITY

Determine the priority of the agent relative to the priority of other tasks running on the system. For valid values and more information on how the setting works, see Agent CPU Resource Control in the Nessus Agent Deployment and User Guide.

NESSUS_NAME Specify the 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.
NESSUS_CA_PATH Specify a custom CA certificate to use to validate the manager's server certificate.
NESSUS_PROXY_SERVER Specify the hostname or IP address of your proxy server.
NESSUS_PROXY_USERNAME Specify the name of a user account that has permissions to access and use the proxy server.
NESSUS_PROXY_PASSWORD Specify the password of the user account that you specified as the username.
NESSUS_PROXY_AGENT Specify the user agent name, if your proxy requires a preset user agent.

Start Nessus Agent Installation

1. Navigate to the folder where you downloaded the Nessus Agent installer.
2. Next, double-click the file name to start the installation process. The Welcome to the InstallShield Wizard for Nessus Agent window appears.

Complete the Windows InstallShield Wizard

Note: You may have to restart your computer to complete installation on Windows.

Note: If you want to include the system tray application in your installation, see Configure and View the System Tray Application in the Nessus Agent Deployment and User Guide.

1. In the Welcome to the InstallShield Wizard for Nessus Agent window, click Next to continue.
2. In the License Agreement window, read the terms of the Tenable, Inc. Nessus software license and subscription agreement.
3. Click I accept the terms of the license agreement.
4. Click Next.
5. In the Destination Folder window, click Next to accept the default installation folder.

-or-

Click Change to browse and select a different folder where you want to install Nessus Agents.

6. In the Configuration Options window, type the Agent Key values:

Field Value
Key (Required) Use the value you from the manager.
Server

(Required) Use the value you from the manager.

• To link to Tenable.io, enter cloud.tenable.com:443.

• To link to Nessus Manager, enter the IP/hostname of the manager with the appended port 8834; for example, 192.0.2.0:8834.

Groups

Specify existing agent group(s) where you want to add the agent.

If you do not specify an agent group during the installation process, you can later add your linked agent to an agent group.

Note: The agent name defaults to the name of the computer where you are installing the agent.

7. Click Next.
8. In the Ready to Install the Program window, click Install.
9. If presented with a User Account Control message, click Yes to allow the Nessus Agent to install.
10. In the InstallShield Wizard Complete window, click Finish.

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 HKLM/Software/Tenable/TAG file. To resolve this issue, replace the value in the HKLM/Software/Tenable/TAG file with a valid UUIDv4 value.