PowerShell for Windows Admins


May 20, 2012  12:40 PM

Using Invoke-WmiMethod to set the DNS servers

Richard Siddaway Richard Siddaway Profile: Richard Siddaway

In the last post I showed that there was an issue with the way the SetDNSServerSearchOrder of the Win32_NetworkAdapterConfiguration class worked

This would work

$nic = Get-WmiObject -Class Win32_NetworkAdapterConfiguration -Filter "Index=7"
$nic.SetDNSServerSearchOrder("10.10.54.201")

but using Invoke-WmiMethod failed

After discussions with Bartek Bielawski (PowerShell MVP) and a bit more digging I found that for multiple DNS servers this would work

$dnsserver = "10.10.54.201", "10.10.54.98"
Get-WmiObject -Class Win32_NetworkAdapterConfiguration  -Filter "Index=7" | Invoke-WmiMethod -Name SetDNSServerSearchOrder -ArgumentList (, $dnsserver)

Its necessary to create an array as the input argument  (, $variable) – its a unary array ie one element array

if you want to use just a single DNS server then you need to use the unary array trick twice – once when you create the variable and again when you use Invoke-wmimethod.  Messy but it works

$dnsserver = (,"10.10.54.201")
Get-WmiObject -Class Win32_NetworkAdapterConfiguration  -Filter "Index=7" | Invoke-WmiMethod -Name SetDNSServerSearchOrder -ArgumentList (, $dnsserver)

 

If you want to use the new CIM cmdlets in PowerShell v3 – its easy if you have multiple DNS servers

$dnsserver = "10.10.54.201", "10.10.54.98"
Get-CimInstance -ClassName Win32_NetworkAdapterConfiguration -Filter "Index=7" | Invoke-CimMethod -MethodName SetDNSServerSearchOrder -Arguments @{DNSServerSearchOrder = $dnsserver}

 

for a single one we just need to create a unary array on the Arguments parameter
$dnsserver = "10.10.54.201"
Get-CimInstance -ClassName Win32_NetworkAdapterConfiguration -Filter "Index=7" | Invoke-CimMethod -MethodName SetDNSServerSearchOrder -Arguments @{DNSServerSearchOrder = (,$dnsserver)}

 

This is not satisfactory because we have to adopt different techniques depending on the number of DNS servers we need to put into NIC property. This is NOT a PowerShell issue – it has to be a WMI issue because the IP address that we saw last time also takes an array and it was very happy with a single value.

Hopefully this is not something that will come up too often but be aware of these options when working with WMI methods

May 20, 2012  4:34 AM

TCP/IP Alternative Configurations: pt IV reset to static address

Richard Siddaway Richard Siddaway Profile: Richard Siddaway

At some stage we may need to reset our NIC back to having a static address

$index = 7            
            
$nic = Get-WmiObject -Class Win32_NetworkAdapterConfiguration `
-Filter "Index=$index"             
            
$ipaddress = @("10.10.54.202")            
$subnet = @("255.255.255.0")            
Invoke-WmiMethod -InputObject $nic -Name EnableStatic -ArgumentList $ipaddress, $subnet            
            
$dnsserver = "10.10.54.201"            
$nic.SetDNSServerSearchOrder($dnsserver)            
            
#Invoke-WmiMethod -InputObject $nic -Name SetDNSServerSearchOrder -ArgumentList $dnsserver

We get the configuration of the NIC and use the EnableStatic method to set the address and subnet

The SetDNSServerSearchOrder method is used to set the DNS server.

Notice I haven’t been able to use Invoke-WmiMethod at this point – I’ve had to call the method directly on the object. There appears to be an issue with the formatting of the DNS server addresses as Invoke-WmiMethod complains that the argument has to be an array.

This is under investigation.

More on using WMI with PowerShell can be found in PowerShell and WMI. Chapter 11 covers network adapters in detail.  More details from www.manning.com/powershellandwmi


May 18, 2012  2:00 PM

TCP/IP Alternative Configurations: pt III set the alternative configuration

Richard Siddaway Richard Siddaway Profile: Richard Siddaway

 

We have seen how to set the NIC to use DHCP to get its address. This post shows how to set the alternative configuration on the NIC. If you just  want APIPA then do nothing – other wise use this script

$HKLM = 2147483650 #HKEY_LOCAL_MACHINE            
            
$index = 7            
$nic = Get-WmiObject -Class Win32_NetworkAdapterConfiguration -Filter "Index=$index"            
            
$key = "SYSTEM\CurrentControlSet\services\Tcpip\Parameters\Interfaces\$($nic.SettingID)"            
            
Invoke-WmiMethod -Class StdRegprov -Name SetDWORDvalue -ArgumentList $hklm, $key, "AddressType", 2            
            
Invoke-WmiMethod -Class StdRegprov -Name SetMULTISTRINGvalue -ArgumentList $hklm, $key, "Alternate_$($nic.SettingID)", "ActiveConfigurations"            
Invoke-WmiMethod -Class StdRegprov -Name SetSTRINGvalue -ArgumentList $hklm, $key, "10.10.54.202", "DhcpIpAddress"            
Invoke-WmiMethod -Class StdRegprov -Name SetSTRINGvalue -ArgumentList $hklm, $key, "10.10.54.201", "DhcpNameServer"            
Invoke-WmiMethod -Class StdRegprov -Name SetSTRINGvalue -ArgumentList $hklm, $key, "255.255.255.0", "DhcpSubnetMask"

Again I’m cheating by defining the NIC in terms of its Index number

The registry key is derived from the SettingID property of the NIC

We then need to set a number of registry values. The AddressType sets the alternative configuration to use our informations rather than APIPA. The ActiveCinfigurations value is set using the SettingID property of the NIC

The address, subnetmask, and names server are set.

If you look carefully at the lines where we use the SetMULTISTRINGvalue and SetSTRINGvalue methods you will notice that we give the hive, key, value and then registry value name  whereas the SetDWORDvalue method we give hive, key, value name and then value.

This is a quirk of Invoke-WmiMethod

The WMI documentation for SetMULTISTRINGvalue and SetSTRINGvalue methods state the parameters should be:

  • hive
  • registry key
  • registry value name
  • value

This order is constant across the Set* methods of the StdRegProv class -  see http://msdn.microsoft.com/en-us/library/windows/desktop/aa393600(v=vs.85).aspx

If we do some investigation

PS> ([wmiclass]"StdRegprov").GetMethodParameters(‘SetSTRINGvalue’)


__GENUS          : 2

__CLASS          : __PARAMETERS

__SUPERCLASS     :

__DYNASTY        : __PARAMETERS

__RELPATH        :

__PROPERTY_COUNT : 4

__DERIVATION     : {}

__SERVER         :

__NAMESPACE      :

__PATH           :

hDefKey          : 2147483650

sSubKeyName      :

sValue           : hello

sValueName       :

This clearly shows we need to give the value before the value name.

the same holds true if we investigate using Get-CimClass in PowerShell v3

Get-CimClass -ClassName StdRegProv |

select -ExpandProperty CimClassMethods |

where Name -eq "SetStringValue" |

select -ExpandProperty Parameters

produces

Name                                         CimType Qualifiers

—-                                         ——- ———-

hDefKey                                      UInt32 {ID, IN}

sSubKeyName                                  String {ID, IN}

sValue                                       String {ID, in}

sValueName                                   String {ID, in}

if we use Invoke-CimMethod its not to much of a problem as we have to provide the value name and value pairs as a hash table we are not relying on argument order.

I’ll post an alternative listing using the CIM cmdlets another time


May 18, 2012  12:07 PM

Advanced PowerShell v3 book

Richard Siddaway Richard Siddaway Profile: Richard Siddaway

Three new chapters are added to the MEAP – Manning Early Access Program

Chapter 3 – Using the PowerShell help system – includes PowerShell v3 Updateable help

Chapter 5 – Working with PSsnapins and Modules

Chapter 9 – Formatting

 

www.manning.com/powershellindepth


May 17, 2012  1:04 PM

Scripting Games 2012 comments: #20 multiple ifs

Richard Siddaway Richard Siddaway Profile: Richard Siddaway

An if statement is used to test a condition and if is true do one thing and do another if it is false. It can be written generically as

if (<condition>){ do stuff}
else {do other stuff}

Sometimes we need to test numerous alternatives. We could use multiple if statements, sometimes we have to nest them which can lead to code like this

Get-WmiObject -Class Win32_LogicalDisk -Filter "DriveType=3" |            
foreach {            
 if ($_.FreeSpace -gt 1tb){Write-Host "Over 1TB of disk space free"}            
 else {             
   if ($_.FreeSpace -ge 500gb){Write-Host "Over 500GB of disk space free"}            
   else {            
     if ($_.FreeSpace -ge 300gb){Write-Host "Over 300GB of disk space free"}            
     else {            
      if ($_.FreeSpace -ge 200gb){Write-Host "Over 300GB of disk space free"}            
      else {            
        if ($_.FreeSpace -ge 100gb){Write-Host "Over 100GB of disk space free"}            
        else {            
          Write-Host "Insufficient disk space"            
        }            
     }            
     }            
   }            
 }             
 }

That’s not fun to write and its even less fun to debug or change

The code can be simplified by using if – elseif – else

Get-WmiObject -Class Win32_LogicalDisk -Filter "DriveType=3" |            
foreach {            
 if ($_.FreeSpace -gt 1tb){Write-Host "Over 1TB of disk space free"}            
 elseif ($_.FreeSpace -ge 500gb){Write-Host "Over 500GB of disk space free"}            
 elseif ($_.FreeSpace -ge 300gb){Write-Host "Over 300GB of disk space free"}            
 elseif ($_.FreeSpace -ge 200gb){Write-Host "Over 300GB of disk space free"}            
 elseif ($_.FreeSpace -ge 100gb){Write-Host "Over 100GB of disk space free"}            
 else{Write-Host "Insufficient disk space"}            
 }

This much more compact and understandable. We can do a better job if we use a switch statement which is similar in concept to if-elseif-else

Get-WmiObject -Class Win32_LogicalDisk -Filter "DriveType=3" |            
foreach {            
 switch ($_.FreeSpace) {            
 {$_ -gt 1tb}   {Write-Host "Over 1TB of disk space free"; break}            
 {$_ -ge 500gb} {Write-Host "Over 500GB of disk space free"; break}            
 {$_ -ge 300gb} {Write-Host "Over 300GB of disk space free"; break}            
 {$_ -ge 200gb} {Write-Host "Over 300GB of disk space free"; break}            
 {$_ -ge 100gb} {Write-Host "Over 100GB of disk space free"; break}            
 default {Write-Host "Insufficient disk space"}            
 }            
 }

We select the object to test and use $_ as a placeholder. Each line in the switch statement is a single test. The default statement is for anything that doesn’t pass any of the preceding tests

One difference between the if statements and switch is that with the if statements as soon as a condition is true testing stops. With switch testing would continue through all tests – break is used to stop that

When you need to perform multiple tests consider using a switch statement – it is less typing and easier to debug


May 16, 2012  3:12 PM

TCP/IP Alternative Configuration: pt II Set DHCP

Richard Siddaway Richard Siddaway Profile: Richard Siddaway

The next step on our journey to an alternative configuration is setting the NIC to use DHCP

I will keep cheating for now and specify the NIC – on my machine I now it is the NIC whose Win32_NetworkAdapterConfiguration has an Index of 7

$index = 7            
Get-WmiObject -Class Win32_NetworkAdapterConfiguration `
-Filter "Index=$index" |            
Invoke-WmiMethod -Name EnableDHCP

This sets the IP address to be obtained automatically via DHCP BUT it doesn’t set the DNS server to be delivered via DHCP. The old static DNS entries are retained.

To resolve this we use the SetDNSServerSearchOrder method without any arguments

$index = 7            
            
$nic = Get-WmiObject -Class Win32_NetworkAdapterConfiguration `
-Filter "Index=$index"             
            
Invoke-WmiMethod -InputObject $nic -Name EnableDHCP            
Invoke-WmiMethod -InputObject $nic -Name SetDNSServerSearchOrder            
            

I’ve modified the script slightly so we create an object for the WMI class and then use that object as the InputObject on two calls to Invoke-WmiMethod

We could have just as easily used

$nic.EnableDHCP()

$nic.SetDNSServerSearchOrder()

Now that we have the NIC set to use DHCP we need to configure the Alternative Configuration

More information on working with network adapters can be found in PowerShell and WMIwww.manning.com/powershellandwmi


May 16, 2012  1:50 PM

Scripting Games 2012 comments: #19 default parameters

Richard Siddaway Richard Siddaway Profile: Richard Siddaway

I often saw scripts that did something like this

function test1 {            
 param (            
   [string]$computername            
 )            
            
if (!$computername){            
  $computername = $env:COMPUTERNAME            
}            
            
Get-WmiObject -Class Win32_OperatingSystem -ComputerName $computername              
}

A function, or script, defines a parameter. The first thing the function does it test the value of the parameter and if it doesn’t exist it sets it to a default value.

No, no, no – you are making work for yourself. 

Get PowerShell to do the work for you

function test2 {            
 param (            
   [string]$computername = $env:COMPUTERNAME            
 )            
            
Get-WmiObject -Class Win32_OperatingSystem -ComputerName $computername              
}

See the difference?

The parameter definition now contains a default value.  If you don’t specify the parameter and a value the default kicks in and the function works.

Cuts down typing and gets PowerShell to do the work.


May 15, 2012  3:26 PM

Scripting Games 2012 comments: #18 computer names

Richard Siddaway Richard Siddaway Profile: Richard Siddaway

I have mentioned computer names a few times. One oddity is accessing the local machine.

There are three options

  • dot  .
  • localhost
  • $env:COMPUTERNAME

There are a number of occasions when . and localhost fail.

For example

PS> Get-EventLog -List -ComputerName .

  Max(K) Retain OverflowAction        Entries Log
  —— —— ————–        ——- —
  20,480      0 OverwriteAsNeeded      21,647 Application
     512      7 OverwriteOlder              0 DemoMate
  20,480      0 OverwriteAsNeeded           0 HardwareEvents
     512      7 OverwriteOlder              0 Internet Explorer
  20,480      0 OverwriteAsNeeded           0 Key Management Service
   8,192      0 OverwriteAsNeeded          10 Media Center
     512      7 OverwriteOlder              0 MyNewLog
     128      0 OverwriteAsNeeded         364 OAlerts
  20,480      0 OverwriteAsNeeded           1 Scripts
                                              Security
  20,480      0 OverwriteAsNeeded      56,135 System
  15,360      0 OverwriteAsNeeded      10,918 Windows PowerShell

PS> Get-EventLog -List -ComputerName localhost
Get-EventLog : The network path was not found.
At line:1 char:13
+ Get-EventLog <<<<  -List -ComputerName localhost
    + CategoryInfo          : NotSpecified: (:) [Get-EventLog], IOException
    + FullyQualifiedErrorId : System.IO.IOException,Microsoft.PowerShell.Commands.GetEventLogCommand

PS> Get-EventLog -List -ComputerName ‘localhost’
Get-EventLog : The network path was not found.
At line:1 char:13
+ Get-EventLog <<<<  -List -ComputerName ‘localhost’
    + CategoryInfo          : NotSpecified: (:) [Get-EventLog], IOException
    + FullyQualifiedErrorId : System.IO.IOException,Microsoft.PowerShell.Commands.GetEventLogCommand

PS> Get-EventLog -List -ComputerName $env:COMPUTERNAME

  Max(K) Retain OverflowAction        Entries Log
  —— —— ————–        ——- —
  20,480      0 OverwriteAsNeeded      21,647 Application
     512      7 OverwriteOlder              0 DemoMate
  20,480      0 OverwriteAsNeeded           0 HardwareEvents
     512      7 OverwriteOlder              0 Internet Explorer
  20,480      0 OverwriteAsNeeded           0 Key Management Service
   8,192      0 OverwriteAsNeeded          10 Media Center
     512      7 OverwriteOlder              0 MyNewLog
     128      0 OverwriteAsNeeded         364 OAlerts
  20,480      0 OverwriteAsNeeded           1 Scripts
                                              Security
  20,480      0 OverwriteAsNeeded      56,135 System
  15,360      0 OverwriteAsNeeded      10,918 Windows PowerShell

Get-EventLog fails with localhost

I always recommend using $env:COMPUTERNAME


May 15, 2012  11:37 AM

Test-Connection on PowerShell v3

Richard Siddaway Richard Siddaway Profile: Richard Siddaway

Following on from the previous post I performed the same tests on PowerShell v3

The behaviour is the same except that

Test-Connection -ComputerName . -Count 4 –AsJob

now give the 4 pings when you receive the job information


May 14, 2012  3:23 PM

Test-Connection oddities

Richard Siddaway Richard Siddaway Profile: Richard Siddaway

I’ve playing around with Test-Connection because I wanted to set up a long running WMI based job and I thought that pinging a machine lots of times would be a good way to do it. Test-Connection uses the Win32-PingStatus class.

I started with this

PS> Test-Connection -ComputerName . -Count 4

Source        Destination     IPV4Address   IPV6Address  Bytes    Time(ms)
——        ———–     ———–   ———–  —–    ——–
RSLAPTOP01    localhost       127.0.0.1        ::1          32       0
RSLAPTOP01    localhost       127.0.0.1        ::1          32       0
RSLAPTOP01    localhost       127.0.0.1        ::1          32       0
RSLAPTOP01    localhost       127.0.0.1        ::1          32       0

Nothing special there.

I then tried this

PS> Test-Connection -ComputerName . -Count 4 -Quiet
False

Huh?

PS> Test-Connection -ComputerName localhost -Count 4 -Quiet
True

Odd

PS> Test-Connection -ComputerName $env:COMPUTERNAME -Count 4 -Quiet
True

Very odd – seems like “.” isn’t liked when running –Quiet.  Another good reason to avoid it

I then tried it as a job

PS> Test-Connection -ComputerName . -Count 4 -AsJob

Id       Name     State      HasMoreData   Location     Command
–       —-     —–      ———–   ——–     ——-
3        Job3     Running    False         .            Test-Connection

PS> Get-Job

Id       Name     State      HasMoreData   Location     Command
–       —-     —–      ———–   ——–     ——-
1        Job1     Completed  True          .            Test-Connection
3        Job3     Completed  True          .            Test-Connection

PS> Receive-Job -Id 3

Source   Destination  IPV4Address  IPV6Address  Bytes    Time(ms)
——   ———–  ———–  ———–  —–    ——–
RSLAPTOP01 localhost    127.0.0.1        ::1       32       0

Only one ping is returned instead of the 4 I was expecting.

Not major problems but something to remember


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