After the upgrade to 12.0, users have problem accessing MGMT GUI page and SSLVPN page.

Edit the customized httpd.conf file in '/nsconfig' folder:
Go to line 166 and search for this line:

LoadModule php5_module              /libexec/libphp5.so

Replace it with:
LoadModule php7_module          /libexec/libphp7.so 

After edit, save the file in '/etc' and '/nsconfig' folder.
Manually restart the process:
/bin/httpd -f /etc/httpd.conf 

If you do not need any customization then just delete the httpd.conf file from '/nsconfig' and '/etc' and reboot the NetScaler. After reboot, correct httpd.conf will be auto-generated on NetScaler.

Note: While editing the file on Secondary, make sure you have HA sync disabled. Otherwise changes will be reverted back as Primary will sync the wrong file content to your node.
 

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Problem Cause

GUI is not working because 'httpd' process is not running. You can check this by running command 'top' and confirming if you see that process in the output.

11.1 version of NetScaler uses php5 version whereas 12.0 uses php7. When an upgrade happens, the httpd.conf file will be picked up from '/nsconfig' folder which will still have php5 version.

This article is relevant to NetScaler's having customization in nshttpd.conf file