Manage Logs

Tenable Nessus Agent has the following default log files:

• nessusd.dump — Agent dump log file used for debugging output.

  Configure nessusd.dump

  1. Open the agent command line interface.

  2. Use the command # nessuscli fix --set setting=value to configure the following settings:

     Name	Setting	Description	Default	Valid Values
     Nessus Dump File Max Files	dumpfile_max_files	Sets the maximum number of the nessusd.dump files kept on disk. If the number exceeds the specified value, the setting deletes the oldest dump file.	100	Integers 1-1000
     Nessus Dump File Max Size	dumpfile_max_size	Sets the maximum size of the nessusd.dump files in MB. If the file size exceeds the maximum size, the setting creates a new dump file.	512	Integers 1-2048

     For more information, see Advanced Settings.

• nessusd.messages — Agent message log.

  Configure nessusd.messages

  1. Open the agent command line interface.

  2. Use the command # nessuscli fix --set setting=value to configure the following settings:

     Name	Setting	Description	Default	Valid Values
     Log File Maximum Files	logfile_max_files	Determines the maximum number of nessusd.messages files that Tenable Nessus Agent keeps on the disk. If the number of nessusd.messages log files exceeds the specified value, Tenable Nessus Agent deletes the oldest log files.	2	Integers 1-1000
     Log File Maximum Size	logfile_max_size	Determines the maximum size of the nessusd.messages file in MB. If the file size exceeds the maximum size, Tenable Nessus Agent creates a new message log file.	10	Integers 1-2048

     For more information, see Advanced Settings.

• backend.log — Agent backend log.

  Configure backend.log

  You can configure log locations and rotation strategies for backend.log by editing the log.json file. You can also configure custom logs by creating a new reporters[x].reporter section and creating a custom file name.

  1. Using a text editor, open the log.json file, located in the corresponding directory:

     • Windows — C:\ProgramData\Tenable\Nessus Agent\nessus\log.json

     • Linux — /opt/nessus_agent/var/nessus/log.json

     • macOS — /Library/NessusAgent/run/var/nessus/log.json

  2. For backend.log, edit or create a reporters[x].reporter section, and add or modify the following parameters:

     Parameter	Default value	Can be modified?	Description
     tags	log, info, warn, error, trace	yes	Determines what log information the log includes. response — Web server activity logs info — Informational logs for a specific task warn — Warning logs for a specific task error — Error logs for a specific task debug — Debugging output verbose — debugging output with more information than debug trace — Logs used to trace output
     type	file	not recommended	Determines the type of the log file.
     rotation_strategy	size	yes	Determines whether the log archives files based on maximum rotation size or rotation time. Valid values: size — Rotate the log based on size, as specified in max_size. daily — Rotate the log based on time, as specified in rotation_time.
     rotation_time	86400 (1 day)	yes	Rotation time in seconds. Only used if rotation_strategy is daily.
     max_size	10485760 (10 MB)	yes	Rotation size in bytes. Only used if rotation_strategy is size.
     max_files	2	yes	Maximum number of files allowed in the file rotation. The maximum number includes the main file, so 10 max_files is 1 main file and 9 backups. If you decrease this number, Tenable Nessus deletes the old logs.
     file	Depends on the operating system and log file	yes	The location and name of the log file. If you change the name of a default Tenable Nessus Agent log file, some advanced settings may not be able to modify the log settings.
     context	true	not recommended	Enables more context information for logs.
     format	system	not recommended	Determines the format of the output. combined — Presents output in a format used for web server logs. system — Presents output in the default operating system log format.

  3. Save the log.json file.

  4. Restart the agent service.

  The agent updates the log settings.

• nessuscli.log — Agent CLI log.

Default Log Locations

The following table describes the default log file locations for each operating system.

Operating System	Log Location
Windows	C:\ProgramData\Tenable\Nessus Agent\nessus\logs
Linux	/opt/nessus_agent/var/nessus/logs
macOS	/Library/NessusAgent/run/var/nessus/logs