Installing virtualization tools onto a virtual machine (VM) is always a good idea, regardless of the hypervisor or VM operating system (OS). Within these sets of tools you'll find virtualization-enhanced network device drivers, disk controller drivers and a management agent designed to provide better integration with the hypervisor. The agent provides performance and heartbeat feedback to the hypervisor.
While installation of the tools is an easy task to perform, it's important to note that you will have to reboot the VM after installation. This is true for any hypervisor tools suite.
The reason you must reboot is that disk controller drivers and some network drivers can't be hot removed and replaced. Rebooting gives the VM an opportunity to use the new drivers from a fresh starting point.
For XenServer-hosted VMs, you can install XenServer Tools by first selecting your XenServer host in XenCenter's Server View window. In the right-hand pane, you'll see a list of hosted VMs on that XenServer. A visible notification link that reads "XenServer Tools not installed" will appear as part of the VM description.
Click the link for "XenServer Tools not installed" and follow the instructions to install the Tools on your VM. The process requires very little interaction from you, other than to accept the EULA before continuing and then to reboot the virtual machine. While rebooting upon completion of the tools installation is optional, it is an essential step.
This need to reboot generally only becomes a problem for production systems. Since there is a reboot involved, it's recommended that you wait until you have a clear maintenance window in which to perform the installation.
I've never had anything go wrong with a tools installation, although I've seen many forum posts regarding errors and problems associated with the installation. In my experience with Citrix XenServer virtualization this installation should be performed independent of any other installation or maintenance. Install the XenServer Tools, reboot, verify that the tools caused no problems and then proceed with any other maintenance, updates or patching that you need to perform.
If anything goes wrong with your installation you can enter Safe Mode or Normal Mode, and then go to Control Panel->Programs->Uninstall a Program. Find "Citrix Tools for Virtual Machines" and uninstall it. Uninstallation requires another reboot, so be aware of that consequence of agent uninstallation.
For those running Windows Server 2012 or Windows 8, you need to know that while you can install XenServer Tools on these operating systems, the installation will fail if you attempt to install the tools as you normally would to currently supported OS versions. You'll receive a message during the installation that XenServer Tools does not support this operating system.
To successfully install XenServer Tools, first mount the
xs-tools.iso file into the virtual DVD drive of the VM, open Windows Explorer on the VM, open Computer, open the CD image (right click->Open), right click the
xensetup.exe file and select Properties.
Select the Compatibility tab, click the "Run this program in compatibility mode for:" checkbox and select Windows 7 from the dropdown menu. Select "Windows 7" for Windows 8 or for Windows Server 2012. Click OK and run xensetup.exe to complete the installation.
Once the system returns from its reboot, notice that the tools installed new device drivers for your disk controller and network interfaces. You also have the new agent service running as Citrix Tools for Virtual Machines.
While I demonstrated this procedure using Citrix XenServer, it should apply to any set of hypervisor's tools. More generally, it applies to any executable not strictly compatible with or designed for Windows 8 or Windows Server 2012.
Until vendors create operating systems that are 100-percent aware they're virtual, you'll need to continue to install hypervisor-specific tools onto them.
Ken Hess is a freelance writer who writes on a variety of open source topics including Linux, databases and virtualization. He is also the coauthor of Practical Virtualization Solutions, released in October 2009. You may reach him through his web site at www.kenhess.com.