Changing or virtualizing the Hosts file with AppV 5

Sometimes, applications require specific host file entries. Often you’d probably be able to get around using DNS to resolve the entries the application really needs. But when you can’t, and you want to virtualise your application using AppV 5, it’ll use the hosts file of the OS instead of the hosts file in the virtualized file system.

To get around this, we can let the AppV client fire off a script to modify the actual OS hosts file upon registration of the AppV application. This is done by modifying the DeploymentConfig.xml file and adding a script to your package, detailed descriptions of how this works can be found here. Basically, you add this between the <Machinescripts> tags in the DeploymentConfig.xml file, example:

;
 c:\windows\system32\wscript.exe
 {AppVPackageRoot}]\Scripts\hostfile_edit.vbs
 
 

The VB code in hostfile_edit.vbs that does the actual work is:

Const ForReading = 1, ForWriting = 2, ForAppending = 8
 Set fso = CreateObject("Scripting.FileSystemObject")
 Set WshShell = CreateObject("WScript.Shell")
 WinDir = WshShell.ExpandEnvironmentStrings("%WinDir%")
 HostsFile = WinDir & "\System32\Drivers\etc\Hosts"
 Set filetxtR = fso.OpenTextFile(HostsFile, ForReading, True)
 DNSEntry1 = "10.0.0.1 HOSTNAME #DESCRIPTION"
If (checkHostfile(filetxtR, DNSEntry1) = True) Then
 WScript.Quit(0)
 Else
 Set filetxtA = fso.OpenTextFile(HostsFile, ForAppending, True)
 filetxtA.WriteLine (DNSEntry1)
 filetxtA.Close
 End If
filetxtR.Close
 WScript.Quit(0)
Public Function checkHostfile(filetxt, lineToCheckFor)
 checkHostfile = False
 Do Until filetxt.AtEndOfStream
 s = filetxt.readline
 If (s = lineToCheckFor) Then
 checkHostfile = True
 Exit Function
 End If
 Loop
 filetxt.Close
 End Function

Office 365: ProvisioningFailedException: The name “XXX” is already being used. Please try another name.

Because I couldn’t find an answer to this issue anywhere else, and Microsoft Support was unable to determine the root cause I’m sharing this with you. During a cutover migration from Exchange 2003 to Office 365, my batchjob failed after the initial sync and was unable to process incremental syncs of emails in Exchange 2003.

The error in the batchjob’s status display for each failed user was:

ProvisioningFailedException: The name “XXX” is already being used. Please try another name.

Solution: delete the batchjob and all the users it provisioned. Recreate and run it again, and this time, don’t edit the primary SMTP address of these users while the job is running, it is used as a foreign key to match between Onprem and Office 365 and confuses the batchjob if it is changed.

The hint I got that gave me an idea of where this issue was coming from was the following error I received a few times (but not consistently) when changing the primary SMTP address of each user:

You can’t use the domain because it’s not an accepted domain for your organization.

The domain was fully validated and the email was not assigned to any other user.

So, don’t mess around while a batchjob is still running 🙂

Elevating powershell scripts, and staying in the script folder

Sometimes you want to be able to just double click your powershell scripts and see them work….putting this code at the top of your script will do just that by detecting if the script is running as administrator with administrative priviledges. If not, the script will launch a new instance of itself with an elevation prompt.

$scriptPath = split-path -parent $MyInvocation.MyCommand.Definition
If (-NOT ([Security.Principal.WindowsPrincipal][Security.Principal.WindowsIdentity]::GetCurrent()).IsInRole([Security.Principal.WindowsBuiltInRole] "Administrator"))
{
 $arguments = "& '" + $myinvocation.mycommand.definition + "'"
 Start-Process powershell -Verb runAs -ArgumentList $arguments
 Break
 }
 cd $scriptPath

DFS Namespace failure

I ran into a hard to find but easy to fix issue today on a Windows 2008 R2 DFS server, the namespace suddenly lost all folder targets and displayed as an empty folder. The eventlog showed the following:

 

Event ID 14534, source DfsSvc: DFS Root xxxxx failed during initialization. The root will not be available.

Additionally, event ID 14503 was logged for each folder target under this namespace.

Solution: remove the server from the namespace, delete the namespace folder on the physical disk and readd the server to the namespace.

Office 365, Azure, Enterprise Mobility and DevOps