Manage Logs

Nessus has the following log files:

  • nessusd.dump — Nessus dump file used for debugging output.
  • nessusd.messages — Nessus scanner log.
  • www_server.log — Nessus web server log.
  • backend.log — Nessus backend log.

Default Log Locations

The following are the default log file locations for each operating system. You can also modify log file locations.

  • Linux — /opt/nessus/var/nessus/logs/<filename>
  • Mac OS X — /Library/Nessus/run/var/nessus/logs/<filename>
  • Windows — C:\ProgramData\Tenable\Nessus\nessus\logs\<filename>

Modify Log Settings

To modify log settings, use either of the following methods:

  • Modify advanced settings — Modify log settings such as logging levels, location of log files, and log rotation strategy.
  • Modify log.json — Modify log settings such as location of log files and log rotation strategy for nessusd.messages, www_server.log, and backend.log. You cannot configure nessusd.dump settings using log.json.

Modify log.json

You can configure log location and rotation strategy by editing the log.json file.

Note: You cannot configure nessusd.dump settings using log.json. Configure nessusd.dump settings using advanced settings.

To modify log settings using log.json:

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

    • Linux — /opt/nessus/var/nessus/log.json
    • Mac OS X /Library/Nessus/run/var/nessus/log.json
    • WindowsC:\ProgramData\Tenable\Nessus\nessus\log.json
  2. For each reporters[x].reporter, add or modify the following parameters.

    Parameter Default value Description
    rotation_strategy size

    Determines whether the log archives files based on rotation time or maximum rotation size.

    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)

    Rotation time in seconds.

    Only used if rotation_strategy is daily.


    Nessus: 536870912 (512 MB)

    Agent: 10485760 (10 MB)

    Rotation size in bytes.

    Only used if rotation_strategy is size.



    Agent: 2

    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, old logs will be deleted.


    Depends on operating system and log file

    The location of the log file. See Default Log Locations.

  3. Save the log.json file.
  4. Restart the Nessus service.

    The log settings are updated.