8.1 VCAP-DCA Study Guide - Getting Started with PowerCLI

Posted on 21 Apr 2011 by Ray Heffer

If you have no or little experience with Windows PowerShell, but want to jump straight into VMware PowerCLI then you may find you have some gaps in the knowledge required to get started. How do you add the VMware PowerCLI snap-in (VMware.VimAutomation.Core) for example? How do you construct a foreach statement? How do you work with variables? There are some excellent resources available on the web, and one of my favourites is Alan Renouf’s website Virtu-Al. He also has a great article on Working with events. Definitely work a look!

Lesson 1: PowerShell ‘Need to Know’

Once you’ve installed PowerCLI, the first thing you should do is set the execution policy to allow RemoteSigned scripts to run. This is only done one time.

Set-ExecutionPolicy RemoteSigned

Tip: Throughout PowerCLI, if you can’t remember a command type part of it and hit Tab to scroll through the available commands. For example, Set-E (hit Tab) will complete the Set-ExecutionPolicy command. Not sure what comes next, then type /? and it will show the list of available values; Unrestricted, RemoteSigned, Allsigned etc.

Special Variables

Variable	Description
$_	Pipeline variable. This is a placeholder for the current (pipeline) object, for example in a foreach loop it will contain the current object in the loop
$?	Status of the last statement that was executed
$Args	Used in creating functions that require parameters
$Env:Path	Environmental path to files
$Error	Recent error messages
$foreach	Refers to the enumerator in a foreach loop
$Home	Home directory of the current user (E.g. %USERPROFILE%)
$True	Returns boolean TRUE
$False	Returns boolean FALSE
$Null	Null

Operators

Operatpr	Description
-eq	equal to
-ne	not equal to
-gt	greater than
-lt	less than
-ge	greater or equal to
-le	less or equal to
-contains	contains
-notcontains	doesn’t contain

Aliases

Type Get-Alias to list all PowerShell aliases. Here are two of the most frequently used ones:

Alias	Description
%	Alias to ForEach-Object cmdlet. This is often used and can be confusing to novices trying to understand other PowerShell scripts!
?	Alias to Where-Object cmdlet

IF Statement

Condition	Description
IF	If (condition) { statement }
	ElseIf (condition) { statement }
	Else (condition) { statement }

Example

if ($vmguest.OSfullname -eq $null) {$vmguest.OSfullname = "Unknown OS"}

ForEach Loop

Loop	Description
ForEach	ForEach ($items in $array) { statement }

Example

$getvm = Get-VM
ForEach ($vm in ($getvm | Where-Object {$_.MemoryMB -lt "2048"})) {
$vm
}

Lesson 2: Getting Started with PowerCLI

First make a connection to vCenter (or an ESX host):

Connect-VIServer -server <vcenter_hostname>

Getting help and examples

Get-Help
Get-Help Get-VMHost
Get-Help Get-VMHost -examples | more
Get-Help Get-VMHost -full | more

This is useful as it brings up the help window which you can then use to search or browse for Cmdlets and examples…

Get-PowerCLIHelp

Get Properties and Methods for an object

Get-VMHost | Get-Member

Get-VM | Get-Member

Let’s start with a basic task, then we’ll break it down to see how the command is constructed:

List all VM’s with a connected CD-ROM

Get-VM | where { $_ | Get-CDDrive | where { $_.ConnectionState.Connected -eq "true" }}

Let’s break this down…

Using Get-VM, pipe this to a where statement…
Use $_ which in this case is our VM (current object)
Pipe this to Get-CDDrive where $_ (current object, in this case the CDDrive) ConnectionState.Connected is true.

So how did I come up with this? Let’s break it down further.

Lets put our Get-VM into a variable $vm

$vm = Get-VM

We could type $vm and it’ll do the same as Get-VM, but now it’s in a variable we can do more with it. For example, try $vm[0], this will get the first VM in the list (or array).

$vm[0]

We could also try:

$vm | where { $_.Name -eq "DC01" }

This would list the VM with the name of DC01.

Now we can focus on one VM at a time, lets see what we can find out. Lets pipe it to Get-CDDrive.

$vm[0] | Get-CDDrive

It doesn’t give us a great deal, so lets pipe format-list (or fl)…

$vm[0] | Get-CDDrive | fl

This is more interesting, notice now we can see ConnectionState and it has Connected:False. So you can see we can use ConnectionState.Connect -eq “true” in our command.

Create a new datacenter called TestDC

You can list existing datacenters with Get-DataCenter. Use Get-Folder to see all items in the hierarchy and datacenters is at the top. To create a new datacenter at the root level we’ll use Get-Folder -NoRecursion.

New-DataCenter -Location (Get-Folder -NoRecursion) -Name TestDC

If you use Get-Datacenter again, you should now see your new datacenter.

Adding a host to the TestDC datacenter

Add-VMHost -Location TestDC -User root -Password **** -force:$true

We need to use -force:$true, otherwise it will fail with an error regarding a self-signed certificate (unless you have a trusted certificate of course).

Placing an ESX host into Maintenance Mode

Set-VMHost -VMHost -State "Maintenance"

or to exit maintenance mode use

Set-VMHost -VMhost -State "Connected"

Create a variable to store your ESX host credentials

$creds = Get-Credential

Connecting to vCenter or ESX

Connect-VIServer -Credential $creds

Add an ESX host to a variable, and use it to retrieve the host properties

$esxhost = Get-VMHost

Get the methods and properties of the host using $esxhost | Get-Member

Display the version of ESX

$esxhost.version

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