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Fixing zPanel blank-screen error

Tags: blank pagephpzpanel

Published on: August 3, 2014 by Shafeer P

Fixing zPanel blank-screen error

Scenario:

Sometimes our zPanel server management clients open support ticket saying that the zPanel homepage or some specific pages (like DNS manager) will shows a blank page (white screen). Since the ZPanel is written in PHP, most cases it will be related to permission issues of PHP functions(). The apache error log will give the specific reason of the problem.

Tracing the problem

Login to the zPanel server using SSH and monitor the apache error log in real-time using the command,

tail -f /var/log/apache2/error.log | grep xx.xx.xx.xx

Note : The IP xx.xx.xx.xx  is your public IP

Now open the zPanel page in web browser which shows error. Return to the error log screen and find the line matching as below,

[Sat Aug 17 03:35:54 2013] [error] [client xx.xx.xx.xx] PHP Warning: system() has been disabled for security reasons in /etc/zpanel/panel/modules/dns_manager/code/controller.ext.php on line 1674, referer: http://IP/?module=dns_manage

From the above error log, it is clear the the issue is related with the PHP function system(), which is disabled. Other functions like exec() will also cause the the white-screen errors.

Allowing the PHP function()
Edit the Apache Virtual Host configuration file,

vi /etc/zpanel/configs/apache/httpd-vhosts.conf

Note : Please keep a backup copy of httpd-vhosts.conf before editing in case if something went wrong!

Find the VirtualHost entry for the Control Panel,

# Configuration for ZPanel control panel.
<VirtualHost *:80>
ServerAdmin admin@hosting.com
DocumentRoot “/etc/zpanel/panel/”
php_admin_value suhosin.executor.func.blacklist “passthru, show_source, shell_exec, system, pcntl_exec, popen, pclose, proc_open, proc_nice, proc_terminate, proc_get_status, proc_close, leak, apache_child_terminate, posix_kill, posix_mkfifo, posix_setpgid, posix_setsid, posix_setuid, escapeshellcmd, escapeshellarg”
ServerName host.hosting.com
ServerAlias *.host.hosting.com
AddType application/x-httpd-php .php
<Directory “/etc/zpanel/panel/”>
Options FollowSymLinks
AllowOverride All
Order allow,deny
Allow from all
</Directory>
# Custom settings are loaded below this line (if any exist)
</VirtualHost>

Have a look at the following line,

php_admin_value suhosin.executor.func.blacklist "passthru, show_source, shell_exec, system, pcntl_exec, popen, pclose, proc_open, proc_nice, proc_terminate, proc_get_status, proc_close, leak, apache_child_terminate, posix_kill, posix_mkfifo, posix_setpgid, posix_setsid, posix_setuid, escapeshellcmd, escapeshellarg"

The function system() is blacklisted, we have remove the entry ‘system’ to allow the execution. Save the configuration file httpd-vhosts.conf

Apply the changes

We need to restart the Apache server to apply the changes

service apache2 restart

Open the phpinfo page to confirm the ‘system’ function is removed from the

suhosin.executor.func.blacklist

 

 

For more assistance you can contact our zPanel server management team

Category : Apache, Linux, Troubleshooting

Shafeer P

Shafeer P

Shafeer is currently working as Senior System Engineer at SupportSages. He is capable of tackling time-consuming issues quickly with his advanced scripting abilities. His unchallenged expertise in solving complex issues in a cut-and-dried way makes him a dependable man in the team. The attitude and philosophy he shows on his workplace make his colleagues call him 'Mr. Perfectionist'. Furthermore, he is a travel and photography enthusiast, and loves to spend his leisure times on music and DIY arts.

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