Troubleshoot Web Interface

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Page under construction. Below you'll find notes that are being collected to make into an article.

Apache Error Logs

You can manually view the apache error logs by either using vim, cat, or tail. The most popular way is with tail so we will demonstrate that way. Often times, problems with the web interface will have associated errors in apache's log file. Researching this error normally leads you to the corrective action necessary - or at least provides you with an error you can post on the forums with your issue.

RHEL/CentOS/Fedora: tail -n 100 /var/log/httpd/error_log

Debian/Ubuntu: tail -n 100 /var/log/apache2/error.log

Fatal error: Allowed memory size of xxxxxxxx bytes exhausted

Reference: Fog Version 5507 Cannot Access Host Management

Solution: Raise the web interface's memory limit: FOG Configuration -> FOG Settings -> General Settings -> FOG_MEMORY_LIMIT

It’s done in megs, so 128 = 128M, 256 = 256M etc…

After changing this, a reboot is recommended.

Manually test WOL

This is the web address to manually test FOG's WOL functionality:


Where x.x.x.x is your FOG server's IP address, and aa:bb:cc:dd:ee:ff is the MAC address of the host you wish to wake up.

For instance, if my FOG server's IP is and the target host's MAC is 14:fe:b5:df:fc:7e I would then put the below web address into the address bar of a web browser and then press enter / click go.

After doing this, the target host will be sent a WOL packet from the FOG server.

Manually check a host's iPXE script

Below is the web address used to check a particular host's iPXE script that the fog server gives it when it's network booting. You would replace x.x.x.x with your fog server's IP address, and replace the MAC address with the host's actual mac address.


High CPU load from web interface

There is a tool called apachetop that will list the amount of requests every file served by Apache receives, along with the total amount of data sent via that file. This tool will prove invaluable in solving web load issues.

To install apachetop on Fedora 23:

dnf install apachetop -y

Then to run it, simply type:


apachetop is available for other distributions too.

Other tools to look into are iftop ran with this command: iftop -n and just plain-old top

See also DB Maintenance commands: Troubleshoot_MySQL#Database_Maintenance_Commands

High CPU load from apache

Here are threads about high CPU load: