With the Daylight Savings Time change this past weekend, Helient has been fielding a number of calls from clients experiencing issues with VDI machine registration, session disconnects, and group policy failures. Whether using Citrix Provisioning Services, Citrix Machine Creation Services, or VMware View Linked Clones, non-persistent machines revert to the base image every time they are booted. Therefore, after the change to Daylight Savings Time the system time on these machines reverts to Standard Time instead of Daylight Time every time they are rebooted until such time as the base image is updated. The effect of this is that the machine’s system clock will not match the time in the Windows Domain for a period of time after a reboot. This, in turn, can lead to issues obtaining IP addresses and authenticating with Domain Controllers which can cause a variety of problems within the desktop and user environment.
Some of these side-effects might include:
• Errors applying machine Group Policies
• Errors logging into the domain
• Login scripts not running
• Errors acquiring / renewing IP addresses from DHCP
• Communication issues with virtual desktop agents
• Failed user connections
• Unregistered machines
After the machine has been running for a period of time the clock will adjust, domain authentication will succeed, and machine policies will apply (assuming background processing of Group Policy is enabled) but it is the period immediately after a restart that can be problematic and cause unusual behavior or even outright failures. Please be aware of this issue and make plans to update your base image since this is the only way to fully remedy this problem. Below are some links for further reference on both VMware View and XenDesktop:
http://support.citrix.com/article/CTX200058
http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=2074301
https://community.spiceworks.com/topic/457578-dhcp-daylight-saving-time-problems
The severity and impact of these issues is dependent on many factors within the environment, such as DHCP lease times and whether Group Policy provides critical settings to machines without which they will not register or function correctly. Many environments can continue to run with the initial clock skew and report no issues. However, the only way to guarantee that none of these issues occur is to update the base image to reflect the current and correct offset for Daylight Savings Time. If you recently began experiencing unusual issues, you should investigate this possibility and update the base image per the vendors’ instructions above as soon as possible.
If you have any questions or need assistance during this transition, please contact us using support@helient.com.