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Remotely query an ESXi host without adding it to vCenter Server

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I was browsing through the vSphere API Reference the other day and I came across an interesting vSphere API called QueryConnectionInfoViaSpec() which was introduced in vSphere 6.0. This new API is similiar to the existing QueryConnectionInfo() method which also allows you to remotely query an ESXi host without requiring you to add it to your vCenter Server Inventory, which I did not know about before. Some of the information that you can retrieve is whether it is currently being managed by an existing vCenter Server and if so, what is its IP Address, any registered Virtual Machines, networks and datastores that may be configured along with underlying host capabilities.

The main difference between this new API is that instead of accepting a list of arguments to the method, it accepts a HostConnectSpec. It is a minor difference, but what this allows you to do is to be able to re-use that exact same spec in the AddHost_Task() API if you determine that you would like to add the ESXi host to your vCenter Server Inventory after inspecting the remote ESXi host. I think this is a useful API if you want to validate that you are not stealing an ESXi host from another managed vCenter Server and if you are, at least you know which vCenter Server it was being managed by. To demonstrate this vSphere API, I have created a simple PowerCLI script called Get-RemoteESXi.ps1 which requires a vCenter Server login as well as the Hostname/IP Address and credentials of the remote ESXi host you wish to query.

Here is an example output of running the script which stores the returned output to the $results variable.

query-remote-esxi-without-adding-to-vcenter-server
If you want to check whether the ESXi host is being managed by an existing vCenter Server, you can check the following property which will hold the IP Address of the vCenter Server if it is currently being managed:

$result.Host.ManagementServerIp

If you want to check if there are running VMs already on the ESXi host, you can check the following property:

$result.vm

As mentioned earlier, there is a ton of other information returned from the remote ESXi host and I will leave it as an exercise for the reader to explore further.

How to automate vSphere MOB operations using PowerShell?

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A couple of weeks back I was investigating something that involved the use of the vSphere Managed Object Browser (MOB) and I needed to automate a particular operation. For those of you not familiar with the vSphere MOB, it is a UI debugging tool that allows you to visualize and invoke vSphere APIs using just a web browser. The vSphere MOB is available on both vCenter Server and ESXi and uses the underlying vSphere API. Outside of learning about the vSphere APIs and potentially for troubleshooting purposes, there really is no good reason to be directly interacting with the vSphere MOB on a regular basis. Customers can use any one of the many vSphere SDK/CLIs to easily automate and interact with the vSphere API.

Having said that, there may be cases where you might want to invoke a specific operation using the vSphere MOB, such as private API for example. Obviously, using any private/internal APIs is not officially supported by VMware and their use will be at your own risk. Nonetheless, I had a specific operation that I needed to call from the vSphere MOB and wanted to do so using PowerShell. Several years back I had demonstrated how you could invoke the vSphere MOB using Python but I could not find any PowerShell examples that actually worked. I figured this would be a good learning opportunity for myself and probably something I or others could benefit in the future.

To provide a concrete example, I will be invoking a supported vSphere API called the QueryOptions which is used for accessing either a vCenter Server or ESXi Advanced Settings. For our example, I will be connecting to the vCenter Server's MOB and will be querying for a specific vCenter Server Advanced Setting. If we were to do this manually in the vSphere MOB, we would first open a web browser and login to the following URL: https://[VC-SERVER]/mob/?moid=VpxSettings&method=queryView

automate-vsphere-mob-using-powercli
If you wanted to see all advanced settings, you would leave the "name" parameter blank. For our example, we will query for the VirtualCenter.InstanceName property as shown in the screenshot above and then click on the "Invoke Method" to execute the vSphere API operation. If successful, it should display the results which in our case is the IP Address of my vCenter Server. Pretty straight forward vSphere MOB example. OK, onto automating this from PowerShell. I have created a sample PowerShell script called automate-vsphere-mob.ps1 which you will need to edit and provide your vCenter Server Hostname/IP Address and the vCenter Server credentials (can be read-only) since we are not performing any write operations.

Here are some more specific details on what is happening in the script for those interested:

  1. Authenticate to the vSphere MOB URL that you wish to invoke using an HTTP GET operation and storing the session into a variable named vmware (Line 28-29)
  2. Extract the hidden vmware-session-nonce property used to prevent Cross-Site Request Forgery (CSRF) (Line 31-40)
  3. Create the body request which must include the vmware-session-nounce property along with the vSphere API payload (Line 42-45)
  4. Invoke the actual vSphere API call using an HTTP POST along with the existing session from Step 1 and body payload
  5. Process the results (this will be specific to API call) and profit! (Line 50-59)

If you now run the script, you will see that the result is exactly what we saw from interactively using the vSphere MOB. Hopefully this will be useful for anyone who may have a need to automate against the vSphere MOB. For those curious on what I was investigating with the vSphere MOB, stay tuned for more details 🙂

Quick Tip - How to quickly find the VM Display Name of your vCenter Server?

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It is a pretty common practice for customers to use their vCenter Server to manage the underlying ESXi host which is also running the vCenter Server VM, sometimes referred to as a self managed vSphere Cluster. For organizations that have a strict naming convention which includes the VM display name as well as the OS hostname (FQDN), it is generally not too difficult to identify the actual VM that is running your vCenter Server.

However, for customers who may not have a VM display name that can easily be associated to their vCenter Server, it can be pretty difficult and time consuming to locate the vCenter Server VM for troubleshooting and/or updating purposes. Historically, this mapping and association has been left to our customers to document whether it is using a sticky, CMDB, vSphere Tags/Folders, etc. to be able to identify some of these more important VMs.

Luckily, there are some built-in mechanisms within vCenter Server itself that we can leverage to help us quickly identify the VM display name of our vCenter Server. Just this week while working on something, I actually came across another method which I think is even easier than the one I was familiar with.

Option #1 (harder) - When vCenter Server detects that it is in a self-managed configuration, it will automatically add a "System" metadata tag (not to be confused with vSphere Tags) to the actual vCenter Server VM. For vCenter Server, the "Tag" will have the value of SYSTEM/COM.VMWARE.VIM.VC which you can query on a VM using the vSphere API. Below is a PowerCLI example exercising the vSphere API:

$vm = Get-VM -name VCSA-60u2
(Get-View $vm).ExtensionData.Tag

quickly_find_vcenter_server_vm_display_name-0
The main issue here with this option is that because this information is at the VM level, you must first find the VM. This means, you would have to iterate through all of your VMs and seeing which has this particular property set with this value.

Option #2 (easier) - As mentioned earlier, I came across this new option by accident while browsing through the vCenter Server Advanced Settings. I noticed an interesting value for the following key: config.registry.key_VCVmId After a quick investigation, I found that vCenter Server also sets this Advanced Setting to the Managed Object Reference (MoRef) ID of the actual vCenter Server VM. This means, in one step, I know exactly which VM is my vCenter Server and I just need to convert the MoRef ID to a VM Object to then query the VM display name. How cool!?

The following PowerCLI example demonstrates how to extract the vCenter Server Advanced Setting, convert the MoRef ID to a VM Object which we can then query for its VM Display Name.

$vc_server = "192.168.1.51"
$vc_username = "*protected email*"
$vc_password = "VMware1!"

$server = Connect-VIServer -Server $vc_server -User $vc_username -Password $vc_password

# Retrieve the MoRef ID from following VC Advanced Setting
$vcMoRef = (Get-AdvancedSetting -Entity $server -Name config.registry.key_VCVmId).Value

# Construct VM from MoRef
$vm = New-Object VMware.Vim.ManagedObjectReference
$vm.Type = "VirtualMachine"
$vm.Value = $vcMoRef

Write-Host "The VM display name of this vCenter Server is"(Get-View $vm).name

Disconnect-viserver $server -confirm:$false

As you can see from the screenshot below, with just a few lines of code, we can quickly figure out our vCenter Server VM regardless if our inventory is 10 or 10,000 VMs. In fact, you can even output the exact ESXi host that is currently running the VM as well, but I will leave that as an exercise for the reader 🙂

quickly_find_vcenter_server_vm_display_name-1