GET UUID of your hosts.

While you can get the uuid of your hosts 1 by 1
https://<HOST>/mob/?moid=ha%2dhost&doPath=hardware%2esystemInfo

but when you have a lot of hosts that is a little time consuming to do that.
This script from http://thephuck.com/scripts/script-to-pull-host-uuid-for-vmware-powercli/
has the ability to get all the uuids from the hosts you have.
Thanks Luke Huckaba!

Worked great

Usage is like this:

Get-VMHostUUID.ps1 -vmhosts ("host1","host2","host3")or

Get-VMHostUUID.ps1 -vc vcenterserver -container cluster1/folder/dc/etc

param([string]$vc = "vc", [string]$container = "container", [string[]]$vmhosts = $null)

#add the snapin, just in case
Add-PSSnapinVMware.VimAutomation.Core

#Show Usage
function usage()
        {
        Write-host -foregroundcolorgreen `n`t"This script is used to pull UUIDs for all hosts provided."
        Write-host -foregroundcolorgreen `n`t"You can either specify -vmhosts as an array:"
        write-host -foregroundcoloryellow `n`t`t"Get-VMHostUUID.ps1 -vmhosts (`"host1`",`"host2`",`"host3`")"
        write-host -foregroundcolorgreen `n`t"or specify -vc and -container, where container is a host name, cluster, folder, datacenter, etc:"
        write-host -foregroundcoloryellow `n`t`t"Get-VMHostUUID.ps1 -vc vcenterserver -container cluster1" `n
    write-host -foregroundcolorgreen `t"if -container is not used, it pulls ALL hosts from the given vCenter" `n
           write-host -foregroundcolorgreen `t"You can use either -vmhosts by itself, or -vc, not a combination of them, and -container is optional."`n
        }

function Get_UUID()
{
    foreach($vmhost in $vmhosts)
        {
           if ($esx -eq 1)
           #do this only if connecting directly to ESX hosts
                {
                connect-viserver $vmhost -credential$vmhost_creds >$NULL 2>&1
                }
        $vmhostUUID= (Get-VMHost $vmhost| Get-View).hardware.systeminfo.uuid
    Write-Host`n
        Write-Host -foregroundcolorgreen "Server: " $vmhost
        write-host -foregroundcolorgreen "UUID: " $vmhostUUID
            if ($esx -eq 1)
            #disconnect from the current ESX host before going to the next one
        {
        disconnect-viserver -confirm:$false
        }
        }
            if($vcenter -eq 1)
        #disconnect from vcenter
        {
        disconnect-viserver -confirm:$false
        }     
}

#check to make sure we have all the args we need
if (($vmhosts -eq $null) -and ($vc -eq "vc"))
    #if vmhosts and vc is not supplied
        {
        usage
    break
        }

elseif (($vmhosts -ne $null) -and ($vc -ne "vc"))
    #if both vmhosts and vc was supplied
        {
        usage
    break
        }

elseif (($vmhosts -ne $null) -and ($container -ne "container"))
    #if both vmhosts and container was supplied
        {
        usage
    break
        }

elseif (($vmhosts -ne $null) -and (($vc -eq "vc") -or ($container -eq "container")))
    #if only vmhosts is used, set our esx variable to 1 and get credentials
        {
    $esx= 1
    $vmhost_creds= $host.ui.PromptForCredential("ESX/ESXi Credentials Required", "Please enter credentials to log into the ESX/ESXi host.", "", "")
    Get_UUID
    }

elseif (($vmhosts -eq $null) -and (($vc -ne "vc") -and ($container -eq "container")))
    #if vc and container are used, set our vcenter variable to 1, get credentials, and populate vmhosts
        {
    $vcenter= 1
    $vc_creds= $host.ui.PromptForCredential("vCenter Credentials Required", "Please enter credentials to log into vCenter.", "", "")
    connect-viserver $vc -credential $vc_creds> $NULL 2>&1
    $vmhosts= get-vmhost| sortname
    Get_UUID
        }

elseif (($vmhosts -eq $null) -and (($vc -ne "vc") -and ($container -ne "container")))
    #if vc and container are used, set our vcenter variable to 1, get credentials, and populate vmhosts
        {
    $vcenter= 1
    $vc_creds= $host.ui.PromptForCredential("vCenter Credentials Required", "Please enter credentials to log into vCenter.", "", "")
    connect-viserver $vc -credential $vc_creds> $NULL 2>&1
    $vmhosts= get-vmhost-location $container| sortname
    Get_UUID
        }

#garbage collection
$vmhost_creds =$null
$vc_creds = $null
$vmhosts = $null
$vc = $null
$container = $null
$esx = $null
$vcenter =$null

Output is something like this:

Server: server1

UUID: 12345678-90ab-cdef-1234-567890abcdef

Server: server2

UUID: 12345678-90ab-cdef-1234-567890abcdef

Server: server3

UUID: 12345678-90ab-cdef-1234-567890abcdef

Pasted from <http://thephuck.com/scripts/script-to-pull-host-uuid-for-vmware-powercli/>