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Using vSphere Lifecycle Manager (vLCM) API to patch group of ESXi hosts

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An interesting vSphere Lifecycle Manager (vLCM) question that has already come up a few times in the past two weeks is whether vLCM can remediate (patch/upgrade) a specific group of ESXi host(s)?

Today, there are two ways in which vLCM can remediate ESXi hosts within a vSphere Cluster. The first is to simply remediate all ESXi hosts within a vSphere Cluster using the Remediate All option.


If a user wishes to exclude specific ESXi host(s) from being remediated, then the only other option is to manually remediate each individual host. To do so, select an ESXi host from the list and then use the Remediate option in the Actions menu as shown in the screenshot below.


For a small environment, manual remediation might be okay for those willing to click through the vSphere UI but it is certainly less than ideal and you are also not taking advantage of the automation and orchestration that vLCM provides in the first place.

Luckily, there is a third option which is to use the vLCM REST API to specify the desired list of ESXi host(s) that want to patch/upgrade and best of all, this is fully automated!

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How to create a customized ESXi ISO without vCenter Server?

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Historically, if you needed to create a customized ESXi ISO that included additional ESXi drivers, your only supported option was to use the vSphere Image Builder service, which has a dependency on vCenter Server. If you have an existing vCenter Server, this was not a problem and you could easily create a customized ESXi ISO using either the vSphere UI (example here) or the CLI with PowerCLI (example here).

Where this becomes a real challenge is for a greenfield or brand new deployment, where the default ESXi ISO can not be used as it does not contain the required networking and/or storage drivers for the desired hardware platform. Although this affects some customers who use hardware from the VMware HCL but it definitely has a bigger impact on the VMware Homelab community or anyone just getting started for the very first time.

While discussing this topic with a colleague recently, I actually came to learn about an alternative solution for creating a customized ESXi ISO without the need of vCenter Server! Thanks to fellow team member Blair Fritz, who now works in the VMware Cloud Product Management team, for the awesome tip.

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Retrieving VM DRS Score using vSphere API and PowerCLI

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VM DRS Score is a new feature that was introduced with the release of vSphere 7.0, check out this blog post by Niels for a closer look at how this feature can benefit your environment.


In the vSphere UI, this information is expressed as both a Cluster DRS Score and a VM DRS Score as shown in the screenshot above.

This information can also be retrieved programmatically using the vSphere API, as alluded in the title of this blog post. Using the vSphere API, there is a new property called SummaryEx under the ClusterComputeResource object which represents a vSphere Cluster from an API point of view. Here, you will find two new properties: drsScore and numVmsPerDrsScoreBucket which maps to the respective information found within the vSphere UI.

To demonstrate how to access these two new properties, below is a small PowerCLI function called Get-DRSScore which uses the vSphere API to retrieve this information and accepts a single parameter which is a vSphere Cluster object by using the Get-Cluster cmdlet.

Function Get-DRSScore {
    param(
        [Parameter(Mandatory=$true)][VMware.VimAutomation.ViCore.Impl.V1.Inventory.ComputeResourceImpl]$Cluster
    )

    $drsScoreBuckets = @("0%-20%","21%-40%","41%-60%","61%-80%","81%-100%")

    $drsScoreResults = $Cluster.ExtensionData.SummaryEx | select DrsScore, NumVmsPerDrsScoreBucket

    Write-Host "Cluster DRS Score: $(${drsScoreResults}.DrsScore)`n"

    Write-Host "VM DRS Score"
    $count = 0
    foreach($i in ${drsScoreBuckets}) {
        Write-Host "${i} - $(${drsScoreResults}.NumVmsPerDrsScoreBucket[$count]) VMs"
        $count++
    }
    Write-Host
}

Here is an example of using the function and the output matches what is shown in the vSphere UI.

Get-DRSScore -Cluster (Get-Cluster Cluster-1)