A safer way to patch ESXi using PowerCLI and VUM

Patching vSphere is fairly straightforward using vSphere Update Manager. You can let vCenter/VUM automate the patching of an entire datacenter or cluster if you want. Many VMware professionals prefer to have more control over how their clusters get patched, and with good reason. Yes, vCenter is capable of figuring out how many hosts can run your cluster via DRS so you can patch multiple hosts at once, but that is a bit scary if you ask me and unless you have a massive cluster, it is not worth the time savings in my opinion. I prefer to patch each host one by one and do some testing of vMotioning VM’s for each host post installation to ensure the host is functioning correctly.

#Requires -Modules VMware.VimAutomation.Core
#Requires -Modules VMware.VumAutomation
 
function Install-VUMPatch
{
    [CmdletBinding()]
    param
    (
    [Parameter(Mandatory=$true)]
    [string]$VCenter,
 
    [Parameter(Mandatory=$true)]
    [pscredential]$Credential,
 
    [Parameter(Mandatory=$true)]
    [string]$ClusterName,
 
    [Parameter(Mandatory=$false)]
    [string]$BaselineName = 'Critical Host Patches (Predefined)',
 
    [Parameter(Mandatory=$true)]
    [string]$VM
    )
    begin
    {
        ##Try connecting to vcenter
        try
        {
            Connect-VIServer $VCenter -Credential $Credential -ErrorAction Stop
        }
        catch
        {
            $ErrorMessage = $_.Exception.Message
            Write-Error $ErrorMessage
            break
        }
    }
    process
    {
        Try
        {
            # Put baseline into variable and validate existence for later use
            $Baseline = Get-Baseline -Name $BaselineName -ErrorAction stop
            # Attach baseline to all hosts in cluster
            Attach-Baseline -Entity $ClusterName -Baseline $Baseline -ErrorAction stop
            # Test compliance against all hosts in cluster
            Test-Compliance -Entity $ClusterName -UpdateType HostPatch -Verbose -ErrorAction stop
            # Build array of noncompliant hosts
            $VMHosts = (Get-Compliance -Entity $ClusterName -Baseline $Baseline -ComplianceStatus NotCompliant -ErrorAction Stop).Entity.Name
            #Copy patches to noncompliant hosts
            Copy-Patch -Entity $VMhosts -Confirm:$false -ErrorAction stop
        }
        Catch
        {
            $ErrorMessage = $_.Exception.Message
            Write-Error $ErrorMessage
            Write-Output 'Error getting $Vmhosts variable'
            break
        }
        # For each noncompliant host install patches
        foreach ($VMhost in $VMHosts)
        {
            Write-Output "Patching $VMHost"
            try
            {
                # Put VMHost in maintenance mode
                Set-VMHost $VMhost -State Maintenance -Confirm:$false -ErrorAction Inquire | Select-Object Name,State | Format-Table -AutoSize
                # Remediate VMHost
                $UpdateTask = Update-Entity -Baseline $baseline -Entity $vmhost -RunAsync -Confirm:$false -ErrorAction Stop
                Start-Sleep -Seconds 05
                # Wait for patch task to complete
                while ($UpdateTask.PercentComplete -ne 100)
                {
                    Write-Progress -Activity "Waiting for $VMhost to finish patch installation" -PercentComplete $UpdateTask.PercentComplete
                    Start-Sleep -seconds 10
                    $UpdateTask = Get-Task -id $UpdateTask.id
                }
                # Check to see if remediation was sucessful
                if ($UpdateTask.State -ne 'Success')
                {
                    Write-Warning "Patch for $VMHost was not successful"
                    Read-Host 'Press enter to continue to next host or CTL+C to exit script'
                    Continue
                }
                # Check to see if host is now in compliance
                $CurrentCompliance = Get-Compliance -Entity $VMHost -Baseline $Baseline -ErrorAction Stop
                if  ($CurrentCompliance.Status -ne 'Compliant')
                {
                    Write-Warning "$VMHost is not compliant"
                    Read-Host 'Press enter to continue to next host or CTL+C to exit script'
                    Continue
                }
                # Set VMHost out of maintenance mode
                Set-VMHost $vmhost -State Connected -Confirm:$false -ErrorAction Inquire | Select-Object Name,State | Format-Table -AutoSize
                # VMotion VM to VMHost and sleep for 3 seconds
                Move-VM -VM $VM -Destination $VMhost -Confirm:$false -ErrorAction Stop | Out-Null
                Start-Sleep -seconds 3
                # Test network connectivity to VM to ensure VMHost is operating correctly
                Test-Connection $VM -Count 4 -Quiet -ErrorAction Stop | Out-Null
                Write-Output "$VMHost patch successful."
            }
            catch
            {
                $ErrorMessage = $_.Exception.Message
                Write-Warning $ErrorMessage
                # Comment out the Read-Host if you do not want the script to prompt after an error.
                Read-Host -Prompt 'Press enter to continue to next VMHost or CTRL + C to exit'
                Continue
            }
        }
    }
    end
    {
        Disconnect-ViServer -Confirm:$False -Force
        Write-Output  'Script completed'
    }
}