Use PowerCLI Set-HardDisk and Invoke-VMScript to increase the size of many virtual machine hard drives

Today I decided that I wanted to increase the C: volume of 20 VMware Horizon View parent virtual machines (the source for 1,000s of linked-clone virtual desktops) from 40 GB to 60 GB. The normal/painful way to do this would be:

• vSphere > select the virtual machine > Edit Settings > change Hard Disk 1 from 40 GB to 60 GB > Okay
• vSphere > power on virtual machine
• vSphere > launch the console to the virtual machine
• vSphere > Console > log into Windows
• vSphere > Console > Windows > launch Disk Manager
• vSphere > Console > Windows > Disk Manager > Action > Rescan Disk
• vSphere > Console > Windows > Disk Manager > select Volume C > right-click Extend Volume
• power off Windows, exit virtual machine console, repeat for the next virtual machine

Seeking to automate this process, I turned to VMware PowerCLI and learned more about these two commandlets:

• Set-HardDisk
• Invoke-VMScript

After finding a few examples and refreshing my memory on how to use DISKPART from a command line, I created this PowerCLI script that successfully increased the size (both in vSphere and Windows) of my targeted virtual machines in just a few minutes.

PowerCLI Set-HardDisk and Invoke-VMScript (plain text version: PowerCLI-Extend-Disks.ps1)

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# PowerCLI-Extend-Disks.ps1
# Must be run in VMware PowerCLI
# Written by Jason Pearce, jasonpearce.com, (2015 June)
# Inspiration from Brian Wuchner, Adam Stahl, and of course Luc Dekens (LucD)
 
# BEGIN Variables
 
# vCenter that contains target VMs
$vCenter="vcenter.example.local"
 
# New hard drive size you want (should be larger than current drive size)
$NewCapacityGB=60
 
# One or more virtual machines you want to target (modify and uncomment this line)
# $VMs=(Get-Cluster -Name "ClusterName" | Get-VM -Name "VM-Prefix-*")
# $VMs=("VM1","VM2","VM3")
 
# Virtual Machine Windows Credentials (a local admin account)
$GuestUser="administrator"
$GuestPassword="password"
 
# END Variables
 
# BEGIN Script
 
# Connect to vCenter via PowerCLI
Connect-VIServer $vCenter
 
# BEGIN foreach loop
foreach ($VM in $VMs) {
 
# Have vSphere PowerCLI increase the size of the first hard drive in each target VM
Get-VM $VM | Get-HardDisk | Where-Object {$_.Name -eq "Hard Disk 1"} | Set-HardDisk -CapacityGB $NewCapacityGB -Confirm:$false
 
# Run DISKPART in the guest OS of each of the specified virtual machines
Invoke-VMScript -VM $VM -ScriptText "ECHO RESCAN > C:\DiskPart.txt && ECHO SELECT Volume C >> C:\DiskPart.txt && ECHO EXTEND >> C:\DiskPart.txt && ECHO EXIT >> C:\DiskPart.txt && DiskPart.exe /s C:\DiskPart.txt && DEL C:\DiskPart.txt /Q" -ScriptType BAT -GuestUser $GuestUser -GuestPassword $GuestPassword
 
}
# END foreach loop
 
# Disconnect from vCenter
Disconnect-VIserver -Confirm:$false
 
# END Script

Note that the script cleans up after itself. It creates a small DiskPart.txt file on the root of your virtual machine, runs DiskPart using the settings in the DiskPart.txt file, and then deletes the DiskPart.txt file when its done.

Now that I know how to use the Invoke-VMScript commandlet, I’m sure I’ll come up with many more time-saving ideas like this one.