Author Archive: Eric

PowerShell: Alternate script behavior when dot sourced vs run directly

I use dot sourcing in my PowerShell scripts to reuse functions* and sometimes I want different behavior if they are included (dot sourced) or run directly. This concept is used in Python to provide an easy way to run tests against the code when run directly but not when it is imported.

You are not restricted to running tests using this approach, but I think that automated testing is useful so that is the example I provide below.

VMware PowerCLI 5 Cmdlets by Noun

Generated using this post.

Noun Verbs
AdvancedSetting Get,New,Remove,Set
AlarmAction Get,New,Remove
AlarmActionTrigger Get,New,Remove
AlarmDefinition Get,Set
Annotation Get,Set
CDDrive Get,New,Remove,Set
Cluster Get,Move,New,Remove,Set
CustomAttribute Get,New,Remove,Set
CustomField New,Remove,Set
Datacenter Get,Move,New,Remove,Set
Datastore Get,New,Remove,Set
DatastoreCluster Get
DatastoreItem Copy
DrsRecommendation Apply,Get
DrsRule Get,New,Remove,Set
ErrorReport Get
EsxCli Get
EsxTop Get
FloppyDrive Get,New,Remove,Set
Folder Get,Move,New,Remove,Set
HAPrimaryVMHost Get
HardDisk Copy,Get,New,Remove,Set
Inventory Get,Move,Remove
IScsiHbaTarget Get,New,Remove,Set
Log Get
LogType Get
NetworkAdapter Get,New,Remove,Set
NicTeamingPolicy Get,Set
OSCustomizationNicMapping Get,New,Remove,Set
OSCustomizationSpec Get,New,Remove,Set
PassthroughDevice Add,Get,Remove
PowerCLIConfiguration Get,Set
PowerCLIVersion Get
ResourcePool Get,Move,New,Remove,Set
ScsiController Get,New,Set
ScsiLun Get,Set
ScsiLunPath Get,Set
Snapshot Get,New,Remove,Set
Stat Get
StatInterval Get,New,Remove,Set
StatType Get
Task Get,Stop,Wait
Template Get,Move,New,Remove,Set
Tools Dismount,Mount,Update,Wait
UsbDevice Get,Remove
VApp Export,Get,Import,Move,New,Remove,Set,Start,Stop
VIAccount Get
VICredentialStoreItem Get,New,Remove
VIEvent Get
View Get
VIObjectByVIView Get
VIPermission Get,New,Remove,Set
VIPrivilege Get
VIProperty Get,New,Remove
VIRole Get,New,Remove,Set
VirtualPortGroup Get,New,Remove,Set
VirtualSwitch Get,New,Remove,Set
VIServer Connect,Disconnect
VM Get,Move,New,Remove,Restart,Set,Start,Stop,Suspend
VMGuest Get,Restart,Shutdown,Suspend
VMGuestFile Copy
VMGuestNetworkInterface Get,Set
VMGuestRoute Get,New,Remove
VMHost Add,Get,Move,Remove,Restart,Set,Start,Stop,Suspend
VMHostAccount Get,New,Remove,Set
VMHostAdvancedConfiguration Get,Set
VMHostAuthentication Get,Set
VMHostAvailableTimeZone Get
VMHostDiagnosticPartition Get,Set
VMHostDisk Get
VMHostDiskPartition Format,Get
VMHostFirewallDefaultPolicy Get,Set
VMHostFirewallException Get,Set
VMHostFirmware Get,Set
VMHostHba Get,Set
VMHostModule Get,Set
VMHostNetwork Get,Set
VMHostNetworkAdapter Get,New,Remove,Set
VmHostNtpServer Add,Get,Remove
VMHostPatch Get,Install
VMHostProfile Apply,Export,Get,Import,New,Remove,Set
VMHostProfileCompliance Test
VMHostProfileRequiredInput Get
VMHostRoute Get,New,Remove,Set
VMHostService Get,Restart,Set,Start,Stop
VMHostSnmp Get,Set,Test
VMHostStartPolicy Get,Set
VMHostStorage Get,Set
VMHostSysLogServer Get,Set
VMQuestion Get,Set
VMResourceConfiguration Get,Set
VMScript Invoke
VMStartPolicy Get,Set

Simple XML output of a data object

I am doing some data collection using PowerShell and the output needs to be a simple XML document string.

The built in cmdlets do a great job when persisting data, but they produce some fairly complicated XML that provides more detail on object types than I can use.

Here is a single function to take a PSObject based data object and turn it into XML. I have also included a test function to show an example of building the data object.

Function Convert-CustomObjectToXml {
Outputs a human readable simple text XML representation of a simple PS object.
The input object to inspect and dump.
The number of levels deep to dump. Defaults to 1.
The name of the root element in the document. Defaults to "root"
.PARAMETER indentString
The string used to indent each level of XML. Defaults to two spaces.
Set to "" to remove indentation.
Outputs a human readable simple text XML representation of a simple PS object.
A PSObject with member types of NoteProperty will be dumped to XML.  Only
nested PSObjects up to the depth specified will be searched. All other
note properties will be ouput using their strings values.
The output consists of node with property names and text nodes containing the
proprty value.
	param (
		[Int32]$depth = 1,
		[String]$rootEl = "root",
		[String]$indentString = "  ",
		[Int32]$indent = 1,
		[switch]$isRoot = $true
	# Output the root element opening tag
	if ($isRoot) {
		"<{0}>" -f $rootEl
	# Iterate through all of the note properties in the object.
	foreach ($prop in (Get-Member -InputObject $object -MemberType NoteProperty)) {
		$child = $object.($prop.Name)
		# Check if the property is an object and we want to dig into it
		if ($child.GetType().Name -eq "PSCustomObject" -and $depth -gt 1) {
			"{0}<{1}>" -f ($indentString * $indent), $prop.Name
				Convert-CustomObjectToXml $child -isRoot:$false -indent ($indent + 1) -depth ($depth - 1) -indentString $indentString
			"{0}<!--{1}-->" -f ($indentString * $indent), $prop.Name
		else {
			# output the element or elements in the case of an array
			foreach ($element in $child) {
				"{0}&lt;{1}&gt;{2}<!--{1}-->" -f ($indentString * $indent), $prop.Name, $element
	# Output the root element closing tag
	if ($isRoot) {
		"<!--{0}-->" -f $rootEl
Function Test-Convert-CustomObjectToXml {
	# Create an example object and then try to dump it to the screen.
	$a = New-Object PSObject
	$a | Add-Member -MemberType NoteProperty -Name "CPU" -Value 4
	$a | Add-Member -MemberType NoteProperty -Name "Memory" -Value 800
	$a | Add-Member -MemberType NoteProperty -Name "NICs" -Value (New-Object PSObject)
	$a.NICs | Add-Member -MemberType NoteProperty -Name "vmnic0" -Value "1000"
	$a.NICs | Add-Member -MemberType NoteProperty -Name "vmnic1" -Value "1000"
	$a.NICs | Add-Member -MemberType NoteProperty -Name "vmnic2" -Value "1000"
	$a.NICs | Add-Member -MemberType NoteProperty -Name "vmnic3" -Value "1000"
	$a | Add-Member -MemberType NoteProperty -Name "VMs" -Value (New-Object PSObject)
	$a.VMs | Add-Member -MemberType NoteProperty -Name "VM" -Value @()
	$a.VMs.VM += "foo"
	$a.VMs.VM += "bar"
	$a.VMs.VM += "bash"
	$a.VMs.VM += "bang"
	Convert-CustomObjectToXml $a
	Convert-CustomObjectToXml $a -depth 10 -rootEl "config"

Some sample output.

  <nics>@{vmnic0=1000; vmnic1=1000; vmnic2=1000; vmnic3=1000}</nics>

Quick Memory Allocation for Limit / Reservation Testing in VMware

I am testing the impact and behavior of memory limits and reservations along with balloon drivers and I needed a quick way to allocate memory in a user program.

PowerShell to the rescue. This isn’t a good method for exact memory allocation, but you can consume MBs to GBs of memory pretty quickly.

# Allocate memory by creating a large string.  Divide the length by 4
# (Unicode size) to get an approximation of the MB allocation. Make
# sure to assign the result to a variable otherwise the memory will be
# reclaimed to the .Net garbage collector
$a = "a" * 256MB/4

Testing TCP Network Firewall Ports from ESXi

As we all transition to ESXi there are certain activities that we need to figure out a new way of doing. One item that comes up in new deployments is making sure that all of the ESXi –> firewall rules are defined correctly.

I do not believe that there is a way to do this from the SDK so its off to Tech Support Mode. Unfortunately there is no telnet, netcat, or other network tool that I typically use.

Python to the rescue:

#!/bin/env python
import sys
import os
from socket import *
def usage():
    print "USAGE: %s <host> <port>" % (sys.argv[0],)
# Check the # of parameters
if not len(sys.argv) == 3:
# Check that the host and the port are appropriate.
    host = sys.argv[1]
    port = int(sys.argv[2])
print "Attempting a TCP connection to host '%s' on port '%s'.\n" % (host, port)
    s = socket(AF_INET, SOCK_STREAM)
    s.connect((host, port))
except Exception, e:
    print "Connection Failed: %s." % (e,)
    print "Connection successful."

Python can also send UDP packets fairly easily, but since there is no connection the only way to tell if the traffic worked is to monitor it on in the network or on the destination side. As a result it is just as easy to do the operation that requires the port and if it fails, set up the traffic monitor.