Category Archives: PowerCLI

PowerCLI and your VM’s GuestID

1364677641-01-bacon_egg

Happy Easter!

Easter eggs can be dyed in many different colors…  just like the many OS’s you can run in a vSphere VM!  (Which is 93 if you count everything you can set New-VM’s GuestID!)

Interestingly, when you deploy a VM using PowerCLI and don’t specify an OS with GuestID it defaults to Windows XP (32 bit):

PowerCLI-DefaultOS

As I found out this can lead to some challenges.  I was running into a problem where it seemed like the VMtools were failing.  This all started occurring when testing an existing project that was working fine in vSphere 5.5 on a new vSphere 6.0 install.  The VM was being deployed by PowerCLI and mounting a OpenSUSE Live ISO to boot which also had open-vm-tools on it so you can run scripts, copy files, etc…

Lets try running a script against our newly created “JustANewVM” which was created without specifying a GuestID and is running OpenSUSE with open-vm-tools.PowerCLI-RunDefaultScriptTypeWhile red is my favorite color, I don’t like it at all in this context!


The corresponding host’s hostd.log file didn’t shed much light on this either, lines 4 and 5 do let us know something’s gone awry:

Now I think there might be a problem with the host.. so I restart hostd and try again, same result.  Next, I vMotion the VM over to another host and run the same command and get these logs:

A completely different error came back, which validates my assumption about the host… OR NOT!  The error in the PowerCLI windows was different as well, telling me that there was not a PowerShell interpreter that could be run.  Running the same command subsequent times still produced the original error.. Now, why vMotioning it seems to change the verbosity level I do not know?  I was glad it did however, as it provided me a the clue into what was going on!  If you look at the logs you can see it’s trying to run cmd.exe on the VM and pass it a powershell “EncodedCommand”.  Cool, but that’s not going to work on a *nix box!  At this point I started looking at why vSphere thought this was a Windows machine and found that the default behavior of New-VM without -GuestID is to make it a Windows XP 32 bit VM as discussed above.

As I could see that it was listed as a Windows XP VM, I powered it off, set the OS to the correct one (otherLinux64Guest in this case) and rebooted.  When I tried to run the command, it failed yet again!  The host logs showed the “VIX_E_FAIL” error initially seen in the host logs.  I decided to restart hostd on the host where the VM was running and after that the PowerCLI command ran fine.

An additional anomaly that I found was that when the VM was powered on and the tools started the C# (fat, and going away someday) client would update the Guest OS: field on the summary page for the VM to be the correct one.  The web-client however did not.  I believe that the different clients are looking at different information, the C# client is most likely looking at the properties in ExtensionData.Summary.Guest where the Web-Client is looking at the ExtensionData.Config properties.  In this case the C# client is more accurate/dynamic, not sure of the reasoning behind this.

* I removed a bunch of bits from the above that weren’t relevant, but it’s clear that these are different sets of data and the different clients look at one or the other to get the OS info.

I hope this helps someone! (perhaps it will help me when I forget what happened here!)

As a follow on, long long ago Frank Denneman and Alan Renouf posted about the dangers of mismatched OS’s and VM settings and a really cool one liner for finding them here:

http://frankdenneman.nl/2009/12/15/impact-of-mismatch-guest-os-type/

Links of thanks:

http://vtagion.com
http://frankdenneman.nl/
http://www.virtu-al.net/