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WYSE Thin OS Devices may fail to authenticate to Windows Domain

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Thin Clients require a boot file in order to get all the information needed for successfully booting up. The boot file contains information about which server to contact to download its OS image and what credentials it should use for authenticating the user, just to mention a few. The process is simple. The thin clients will PXE boot into the network, contact the FTP server, get the boot file from the FTP server, and then read the information which tells it what server to contact to download the OS image and what credentials to use in order to authenticate into the OS.

Keeping the above in mind will equip you with a systematic approach when it comes to troubleshooting any issues that you might face with thin clients. Basically issues that might render a thin client unable to load the OS image or boot can be classified into three categories:
  1. Inability to contact the FTP server
  2. Inability to load the OS image
  3. Inability to authenticate
An interruption to the network connectivity, unavailability or misconfiguration of the scope options of the DHCP server, or unavailability of the FTP server are all possible causes to the first category. In other words, if the first categorical issue happens, you need to do the following:
  1. Check the network connectivity between the thin client and both the DHCP server and the FTP server
  2. Ensure that the DHCP server is up and reachable
  3. Ensure that the DHCP scope options specify the correct FTP server
  4. Ensure that the FTP server is up and reachable
The second category pertains to the connectivity to the provisioning server from which the thin client will draw the OS image. Therefore, you need to make sure that the server is up and reachable. You also need to make sure that the server has the intended image that the thin client is requesting. Another reason for not being able to load the OS image might relate to incorrect configuration of the boot file. You need to ensure that the boot file contains the correct information of the provisioning server. In fact an issue with the boot file is the main cause for the third category as well.

In this article I am going to discuss a specific case I have resolved some time back that caused WYSE Thin clients unable to login and retrieve the hosted apps of the users. In more details, the WYSE Thin OS device booted, connected to a FTP server and successfully retrieved the WNOS.ini file (the boot file). However, it immediately restarted afterwards and booted to the Thin OS login screen. Then it failed to authenticate as domain credentials were not accepted by Citrix XenApp.

Symptoms

WYSE Thin OS device boots, connects to FTP server and successfully retrieves WNOS.ini file. However, it immediately restarts and boots to the Thin OS login screen. Then it fails to authenticate as domain credentials are not accepted by Citrix XenApp.
 

Cause

WYSE Thin OS INI files (WNOS.ini) follow standard INI formatting conventions. Parameters are inserted into the file to dictate configurations deviating from the default. When doing so, global connect parameters need to be listed first before other connect parameters. The authentication failure issue was caused by misplacing the domainname parameter. A sample (just for the sake of example) of the .ini file follows:
 
Signon=0
privilege=HIGH
AutoLoad=1
domainname=MyDomain

deskcolor=”0 51 153”
TimeServer=MyTimeServer.MyDomain\
timeformat=”12-hour format” \
DateFormat=”mm/dd/yyyy”

connect=ica \
Description=”Citrix Xenapp 6.5 Environment” \
host=<My Host IP> \
Icon=default \
username=MyUser.ID \
password=MyPassword \
autoconnect=no

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For more information on how to construct your WNOS.ini file please consult this reference guide: http://www.freewysemonkeys.com/downloads/wtos/Wyse%20Thin%20OS%2064%20Parameters.pdf
 

Resolution

Change the position of the parameter domainname to put it under the section of the parameter connect=ica. The following is the modified version of our example:

Signon=0
privilege=HIGH
AutoLoad=1

deskcolor=”0 51 153”
TimeServer=MyTimeServer.MyDomain\
timeformat=”12-hour format” \
DateFormat=”mm/dd/yyyy”

connect=ica \
Description=”Citrix Xenapp 6.5 Environment” \
host=<My Host IP> \
Icon=default \
username=MyUser.ID \
password=MyPassword \
domainname=MyDomain \
autoconnect=no

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Author:Ayman Bakr
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