Advanced Windows PowerShell Scripting Video Training

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Advanced Windows PowerShell Scripting Video Training

Wednesday, March 9, 2016

Just for fun - Storing BLOB files as XML

So, one of the reasons why I like to teach PowerShell is that every once and a while, someone comes up with an unusual idea. So here it goes.  Can you save a BLOB file in an XML file?  This is strictly for the sake of theory.  In the process, we discovered some different behavior of Get-Content.
Off the top of my head, the only way that I knew how to create a BLOB file is with an Offline Domain Join.  Here is the Wikipedia definition of a BLOB:

A Binary Large Object (BLOB) is a collection of binary data stored as a single entity in a database management system. Blobs are typically images, audio or other multimedia objects, though sometimes binary executable code is stored as a blob.

An Offline Domain Join allows you to create an object in Active Directory for a new client without the client being available.  It also allows to client to be configured to join the domain once it is able to contact a Domain Controller.  To get this to work, you need to create a BLOB file with the DJoin command and send that BLOB file to the client. 

So, here we go….

This will execute the provisioning portion of an ODJ.  Since this is a PowerShell class, I used Invoke-Expression.

# Offline Domain Join

Invoke-Expression -Command "djoin /provision /domain /machine LON-SVR1 /SaveFile C:\PS\DJoin.txt"

Here is what the BLOB file looks like.  Not much to look at.
# View the BLOB
Get-Content -Path C:\ps\DJoin.txt

# Save as an CliXML
Get-Content -Path C:\ps\DJoin.txt | Export-Clixml -Path c:\ps\DJoin.xml

# View the XML File
Notepad C:\ps\DJoin.xml
Unfortunately, I cannot display the XML file in this blog.  Go ahead and take a look at it. Keep scrolling down, something is not right.  This is what threw my off.  Take a close look.  There is a lot more information here than the String object sent to Export-CliXML.  As a matter of fact, I’m seeing the size of my hard drive!!!! The reason is that Get-Content added a few note properties.

PS C:\> Get-Content -Path C:\ps\DJoin.xml | Get-Member -MemberType NoteProperty

   TypeName: System.String

Name         MemberType   Definition                                                                        
----         ----------   ----------                                                                         
PSChildName  NoteProperty System.String PSChildName=DJoin.xml                                               
PSDrive      NoteProperty System.Management.Automation.PSDriveInfo PSDrive=C                                
PSParentPath NoteProperty System.String PSParentPath=C:\ps                                                  
PSPath       NoteProperty System.String PSPath=C:\ps\DJoin.xml                                              
PSProvider   NoteProperty System.Management.Automation.ProviderInfo PSProvider=Microsoft.PowerShell.Core\F...
ReadCount    NoteProperty System.Int64 ReadCount=1                                                          

These are not part of a normal string object.  These note properties are responcible for some of the excess information in the XML.  At this point, I was thinking that this is going to fail at the client end.  In any case, the provisioning worked:
PS C:\ps> Get-ADComputer -Identity LON-SVR1

DistinguishedName : CN=LON-SVR1,CN=Computers,DC=Adatum,DC=com
DNSHostName       :
Enabled           : True
Name              : LON-SVR1
ObjectClass       : computer
ObjectGUID        : b2c4be2e-bcbb-48cc-be8c-18313600d8ac
SamAccountName    : LON-SVR1$
SID               : S-1-5-21-1203837507-141498335-1392284353-4103
UserPrincipalName : 

Next we manually copied the XML file to the destination client and executed these commands.
# Create a new directory.
New-Item -Path c: -Name PS -ItemType Directory

# Import the XML File
Import-Clixml -Path C:\ps\DJoin.xml | Out-file -FilePath c:\ps\djoin.txt

Invoke-Expression -Command "djoin /requestodj /loadfile c:\ps\djoin.txt  /WindowsPath c:\Windows /localos"

We received the normal restart required command and after the restart, the client was on the domain. Surprise!!!!!
OK, again, this was just for the sake of theory.  No practical usage was implied.  We were just having some fun.

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