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Moustafa
Staff
Moustafa
Staff
March 23, 2026

Troubleshooting Tip: Downloading and analyzing NMON logs on FortiWeb

  • March 23, 2026
  • 0 replies
  • 75 views
Description This article describes how to download FortiWeb NMON logs (Nigel's Monitor) and analyze them to troubleshoot performance issues such as high CPU usage, memory pressure, disk I/O bottlenecks, or traffic bursts.
Scope FortiWeb v6.4.0 and later.
Solution
  1. Understand where NMON logs are stored.

FortiWeb generates NMON log files (suffix .nmon) automatically.

 

On the FortiWeb system, they are stored under:

 

/var/log/debug/tmp

Key behavior:

  • Sampling interval is 5 minutes.
  • A new .nmon file is created each time the system boots.
  • Typically, there is one file per day; multiple files in the same day usually indicates the unit rebooted or crashed.
  • Maximum stored locally: 180 .nmon files (rotation applies).

 

  1. Download NMON logs from the GUI:
  1. Make sure the Debug menu is visible: System -> Config -> Feature Visibility -> Debug.

  2. Download the debug archive:

    • System -> Maintenance -> Debug -> Download.
    • This downloads console_log.tar.gz.
    • Note: Access requires an admin profile with the relevant permissions (prof_admin).
  3. Extract console_log.tar.gz.
  4. Locate the NMON files in the extracted content:

    • The nmon log files will be found at â€¦\var\log\debug\http_download_log\nmon

    • Note: Folder layout can differ between versions, so a reliable approach is to search for *.nmon.
  1. Analyze the .nmon files:
  • .nmon files are plain text, but analysis is much easier with a 3rd party analyzer that graphs CPU, memory, disk, and network metrics over time.
  • Example: nmon Analyser, which is a Microsoft Excel workbook with macros: Nmon-Analyser.

 

Related document:

Customizing and downloading debug logs 
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