Training resources for VCP on vSphere 4.

Vladan Seget has posted some links to training resources for VCP on vSphere 4.

It doesn’t look like I’ll have time to do the upgrade course this year, which means, as a VCP ion VI3, I won’t be eligible to bypass the “What’s New” course (see below).

VCP on vSphere certification now available

The VCP on VI4 certification is now available.

Registration for the VCP4 exam will open on August 14th. The first exam date available will be August 25th.

Export and import customization profiles using PowerShell

I’m in the middle of preparing for a migration from VI3 to vSphere 4 just now (hence the lack of substantial updating on this site).

As part of this process, I was just about to start writing  a script to export our customisation specifications, when Arnim van Lieshout’s post appeared in my VMware Planet V12N RSS feed.

Export and import customization profiles using Powershell | Arnim van Lieshout.

It failed on a couple of customisations, but by adding…

Write-Host Exporting $CustomizationProfile.name

…after the ForEach loop started, it was easy to see that it was customisations with “/” and “*” characters that were causing the errors.

VMware Developer CodeCentral

VMware have launched a new community site for code examples, and there’s a section on VMware vSphere PowerCLI (formerly VI Toolkit).

They seem to be picking the best scripts from the regular contributors to the forums, so it’s a good place to have a look for examples. They’re rated by users, and tend to be slightly better documented than the ones posted in the forums (which tend to be appended and amended as the thread progresses).

vSphere Evaluator’s Guide

Eric Siebert at vSphere-Land.com points out that VMware have published a 120-page vSphere Evaluator’s Guide that’s chock-full of information about the new features (including a nice little demo of PowerCLI).

Definitely worth checking out.

VMware’s vSphere 4 Cheat Sheet

VMware’s vSphere 4 PDF cheat sheet from boche.net.

“VMware supports 4x more guest operating systems than Microsoft. In fact, VMware supports more versions of Windows than Microsoft.”

pwned!

Thin Provisioning in ESX 3.5

One of the nice new features of vSphere 4 is thin provisioning of virtual disks. Thin provisioned (TP) disks will be familiar if you’ve ever used VMware Workstation where they are used by default, (you need to select Allocate All Disk Space Now to create thick disks). Essentially, rather than allocate all disk space at creation, disk space is allocated on the fly, meaning that a 50GB virtual disk with only 5GB being used by the guest, would only consume 5GB of space. This can obviously result in real savings, but it does have an impact on machine performance due to the increased disk provisioning overhead as the machine grows.

VirtualGeek had an interesting article on thin-provisioning in vSphere 4, and whether this should be done at the VM level, or at the array level. As well as containing a good description of the different disk types (Thick, Thin & Eagerzeroedthick), there was a brief mention of using TP disks in VI 3.5. This was the first time I’d heard of this, and despite it’s unsupported nature, it deserved some consideration. We’re still using VI 3.5, and disk space is probably our number one capacity constraint; the potential opportunity to reduce our disk-footprint without investing in any new hardware or software was too good to pass up.

I soon discovered that we already used TP disks in a very limited way. One of the options in vCenter’s Clone to Template operation allows the creation of a compact template, and we had been using this to reduce the amount of space used by templates. Templates created in this manner use TP disks, and if you convert that template to a machine, the machine inherits the TP disk. However VMs deployed from the template are created with normal (thick) disks. If you’re curious to see if you’ve got any existing TP machines, Eric Gray wrote a PowerShell script to find existing thin provisioned disks.

After only a little more digging, my dream of being lauded for increasing our free space overnight came to an end. In an article on Virtual Future, Sven Huisman wrote:

Apparently, when you move a VM with a thinprovisioned disk from vCenter server, it converts to a thick-disk. This is because thinprovisioned disks is not integrated with vCenter server yet.

Also, when you deploy from a template with a thinprovisioned disk, the new VM will get a thick-disk.

I imagine this is what they mean by “unsupported”, and this is why the TP functionality in VI 3.5 is largely undocumented.

This changes the conversion process from a one-off time-consuming action to something that would need to be done on an ongoing basis. I think we’ll just have to wait until we get the chance to upgrade to vSphere 4.

vSphere PowerCLI.

While speaking to a gentleman from VMware last year, I gently chided Citrix for their grand-renaming, and made comment that at least VMware didn’t succumb to this modern plague of replacing perfectly good names with ones formed from pure marketing-fluff. It was shortly after this that VMware announced the change from Virtual Infrastructure to vSphere.

Alongside this well publicised change; VMware Toolkit (for Windows) is now called vSphere PowerCLI.

I sometimes wonder if all this random capitalisation is part of some great scheme to prevent the world’s pinky fingers from atrophy by having them constantly reach for the Shift key.

There’s also a Twitter account, if you’re into that sort of thing.

Introduction to using VMware vSphere PowerCLI

About 2 years ago, I moved from working as an application packager, and being responsible for two or three (VMware Workstation) virtual machines, to working on the supporting infrastructure for over 200 packagers who require around 700 virtual machines on VMware vSphere (which was at that point called VMware ESX).

While I was (and I still am) impressed by VMware’s hypervisor based virtualisation, there were a few things that started to grate with such an otherwise excellent product:-

• Performing repetitive tasks – for example setting a group of virtual hard-drives to non-persistent – using the vSphere Client GUI was time-consuming (and RSI inducing!).
• There was also no real way of extracting information from vCenter in any structured way. For example, if I wanted to know how many of our Microsoft Windows XP guests had over 512MB RAM allocated to them, they had to be counted manually.

I had a look into running scripts on the host, and toyed with the Remote CLI Appliance, but it was the VMware PowerCLI that unlocked the functionality I’d been looking for.

VMware PowerCLI (formerly VI Toolkit for Windows)  utilises Windows PowerShell to provide a command-line driven interface for your virtual infrastructure. This can dramatically reduce the amount of time taken to perform almost all batch-style tasks and also enables some pretty advanced reporting functionality.

This is nowhere near a proper introduction in how to use PowerShell, but should give enough information to get you started, and hopefully make you want to find out more.

PowerCLI pre-requisites

Powershell is included in Windows 7, and Server 2008, but if it’s not included in your version of Windows, you’ll need to  download and install the appropriate version of Windows PowerShell for your operating system.

Then you need to download and install VMware vSphere PowerCLI (registration required).

If you’re running  PowerShell for the first time you need to change the default execution policy.  To do this:

1. As a user with local Administrator rights, run Windows PowerShell  (on machines with UAC, right-click and Run as Administrator)
2. In that window – run the command

Set-ExecutionPolicy - ExecutionPolicy RemoteSigned

This allows you to run local scripts which have not been signed with a digital signature (which will almost certainly include the scripts you’re using to learn). Scripts from remote sources will still require signing.

Security considerations

The PowerShell security model is designed to address some of the  failures of VBScript – a common virus attack vector. PowerShell scripts (which have a PS1 suffix) do not run by default when invoked in Windows.  Also, as noted above, the default execution policy is not to run unsigned scripts. In order to run a script, you need to modify the execution policy, and then run the script name from the command line. This helps to prevent them from being launched by accident.

In vSphere, users running PowerCLI scripts  have the same permissions as they would get if they logged into vSphere Client. However, as with all scripting languages,  when modifications can be  made easier and faster, the potential impact of mistakes is made greater. PowerShell includes specific measures to alleviate risk, and it’s worth being familiar with this functionality before trying anything more complex.

PowerShell fundamentals

PowerShell works using cmdlets. These are typically fairly descriptive, and great care has been taken to make them work in a consistent and logical way. Most cmdlets follow the format verb-noun, with modifiers for the target of the action, and any cmdlet specific options. They are not case sensitive.

The downside of the commands being so descriptive is that they are sometimes quite long. In order to alleviate this PowerShell allows Aliases to be created. Most common Windows Shell commands already exist in PowerShell as aliases. For example CD, DIR, CLS & REN all work as expected. I find these quite useful when working interactively (entering commands at the prompt for immediate execution), but I tend to avoid them in scripts for the sake of consistency and clarity.

When launching scripts, you need to use absolute paths. For example, if you want to launch the script C:\Scripts\ExampleScript.ps1, when you’re in C:\Scripts you would either need to enter the whole path, or use  ./ExampleScript.ps1.

In order to use PowerShell, you need to import the VI commands using

Add-PSSnapin VMware.VimAutomation.Core

Running the VMware vSphere PowerCLI shortcut created when you install the application does this on launch.

Running the standard PowerShell shortcut does not.

You can however add it to your PowerShell profile, which will enable it in all PowerShell sessions, no matter which shortcut you use to launch them.

PowerShell is object-oriented, meaning that the information returned from commands can be easily used as the input for another command.

If you want to put comments into your scripts, PowerShell ignores anything after the #symbol.

Some simple Cmdlets

Here are a couple of commands to get you started. Open up the PowerCLI command line using the VMware vSphere PowerCLI shortcut, then enter them as shown.

Get-Help

Can display help on the various cmdlets. Running this as above shows the syntax for getting help.

Get-Command

Use to find out all the commands containing certain keywords. For example…

Get-Command *-VM

…uses the wildcard character (*) to show all commands that end with VM, this shows all the  cmdlets that can be used to operate on Virtual Machines. Let’s try a simple one…

Get-VM

You should now get an error message saying “You are not currently connected to any servers. Please connect first using Connect-VIServer or one of its aliases.”. Let’s do that…

Connect-VIServer Name_of_your_vCenter_Server

This uses your current windows credentials to connects to the specified server.  You need to do this before you run any VMware specific PowerShell commands. Now try this again…

Get-VM

You should now be looking at a list of virtual machines managed by your vCenter server.  You can reduce the scope by adding switches, for example…

Get-VM –Name A*

…gets all machines with names starting “A”. For more information, try

Get-Help Get-VM -Detailed

Variables in PowerShell are always preceded by a $ symbol. You can set a variable to the result of any kind of PowerShell command, for example, you can store the results of a Get-VM in a variable…

$objVMs = Get-VM

then use that variable any time you need it, typing

$objVMs

Will display the virtual machine objects stored in the variable. This variable is a collection of objects, each object representing a virtual machine, so we can run more commands against this variable:

Get-VMGuest -VM $objVMs

This lists the State, IP Address and guest OS of all your machine objects.

Instead of using variables for commands like this, you can also pipe the result of one command, straight into another. The equivalent of the above command, using pipes rather than variables is

Get-VM | Get-VMGuest

The objects output byt he first command are piped straight into the second command. Pipes are used extensively in PowerShell, and many cmdlets can be linked together using pipes. This means you can run some complex commands in PowerShell at the command prompt in one line, rather than resorting to writing a script.

Have a  play around with these commands in your test environment before moving onto the next section. As long as you’re using Get- based commands, (rather than Set- or Remove-) you shouldn’t make any changes, but append -WhatIf and/or -Confirm to the end of your Cmdlets if you’re feeling extra-cautious.

Example scripts

Like batch files, PowerShell scripts are simply collections of commands linked together into a text file.

Here are a couple of example scripts, showing what can be done.  Copy into notepad, and save with a PS1 extension. You should run Connect-VIServer interactively before running any of the scripts (or add it as the first line to the script file).

Get information about a specific machine

$strVm = Read-Host "Please enter the VM name"
$vm = Get-VM -Name $strVm
if ($vm.PowerState -eq "PoweredOn") {
$event = Get-VIEvent -Entity $vm | Where-Object {$_.fullFormattedMessage -like "Task: Power on Virtual Machine"}
$VM.Name
$VM.PowerState
(Get-VMGuest -VM $VM).IPAddress[0]
if ($event -eq $null) { Set-Variable -Name user -Value "N/A" } else { Set-Variable -Name user -Value $event[0].username }
$strMessageText = "Machine: " + $VM.Name + "`n" + "Power State: " + $VM.PowerState + "`n" + "IP Address: " + (Get-VMGuest -VM $VM).IPAddress[0] + "`n" + "Switched on by: " + $user
$strMessageText
}
else
{Write-Host "Machine not powered on"}

This script asks the user for a machine name (using Read-Host), then converts that string to a computer object, then (assuming the machine is switched on and VMware Tools is running), displays the DNS name, IP address and the username of the last user to power on the machine (as shown in the machine’s Event Log). The `n is a carriage return.

Get All Windows XP Machines with more than 2Gb of RAM

ForEach ($strMachine in (get-vm | Where-Object {$_.MemoryMB -gt "2000"})){
Get-VMGuest -VM $strMachine | Where-Object {$_.OSFullName -like "Microsoft Windows XP Professional*"} | Select-Object VMName, IPAddress
}

This script could easily be modified and used as a component to make modifications on machines fulfilling certain criteria.

What else can you do?

Almost anything that can be done in the GUI can be done in PowerShell.  Machines can be deployed, customized, switched on, migrated between hosts and resource pools etc. Or you could get the last time a machine was switched on, and by whom.

You can also use PowerCLI to report on the status of guests and hosts. Check out Alan Renouf’s excellent PowerCLI Daily Report, or Hugo Peeter’s script to track free space in your datastores.

One drawback of the API is that performance of cmdlets (especially Get-VM) is quite slow.  Hopefully this will be addressed in future versions.

Further resources

There are many tools, example scripts and on-line resources available. Your first stop for help should be the VMware vSphere PowerCLI Community. I also recommend you keep Alan Renouf’s PowerCLI reference card close-to-hand when you’re just starting out.