Friday, July 06, 2012

More on PowerShell as the Default Shell in Server Core 2012

Yesterday, I posted an article showing how easy it was/is to change your default shell inside Windows Server 2012’s Server Core installation option, and I’ve been playing around with it a bit more. I also noticed Paul Gregory’s blog post on the subject.

The shell that Windows Server 2012 uses to determine which shell to run is at: Hklm:\SOFTWARE\Microsoft\Windows NT\CurrentVersion\winlogon" in the Shell item property.  In Server 2012, this is set, by default, to Explorer.exe. I’m still not quite sure how Explorer knows to load CMD.exe, but it seems to!

To change the shell is simple – just run a variation on: Set-ItemProperty -Path $RegPath -Name Shell -Value 'PowerShell.exe'.

By some variation – I mean you can, in the value entry, specify parameters to PowerShell at startup. If you just want a plain old shell, with all 4 profile files attempted, then leaving the Shell value to just “PowerShell.exe” is fine. But here are some other parameters you could also specify:

  • -MTA, –STA – you can specify to always start up PowerShell in a single threaded or multithreaded apartment. –STA is the default, but if you always need an MTA on a given server, you can.
  • -PSConsoleFile – you can create a console by configuring PowerShell the way you want it to run, then use Export-Console. This might be useful on a single function server to pre-load specific modules, but you’d need to work out how to manage the exported console (where do you put it, how do you update it, etc).
  • -NoProfile – speeds up startup, and is arguably a tad safer. You could theoretically get your profiles ‘infected’ – this option avoids such malware running.
  • -EncodedCommand – accepts a base-64 encoded string – useful if you have to pass a command to PowerShell that requires complex quoting, and use of braces ({}).
  • -Command, –NoExit – you can get PowerShell to run a command, over and above the profile files by specifiying the Command parameter. If you use the Command parameter, you should also specify –NoExit to avoid PowerShell from running the command and immediately exiting!
  • -Version – starts a specific version of PowerShell. This is useful to get PowerShell to start up in V2 on Server 2012, where V3 would of course be the default.

There are a few more parameters, but those are the key ones.


Thursday, July 05, 2012

Making PowerShell the Default Shell in Server 2012 Server Core

Server Core, in Windows Server 2012, is a much improved version of this installation option, first introduced in Windows Server 2008. At the time Server Core was first introduced, it made sense to make CMD.EXE the default shell. Heck – PowerShell could not even run in that environment. But times move on and in Windows Server 2012, Microsoft install PowerShell by default in Server Core. But the legacy of CMD.EXE still remains – at least by default
Turns out it’s just a registry setting to tell Winlogon what shell to start-up at boot time. Thanks to a post by Jeff Hicks, I knew where in the registry the key was, and thanks to James O’Neill, I knew what to put in the value! Setting it is then remarkably easy:

$RegPath = "Microsoft.PowerShell.Core\Registry::HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\winlogon"
Set-ItemProperty -Confirm  -Path $RegPath -Name Shell -Value 'PowerShell.exe -noExit -Command "$psversiontable'

After rebooting – you have PowerShell as your default shell in Server Core. If you are brave, you could just even the –Confirm from the Set-ItemProperty!

Adding (and removing) the GUI From Server Core in Server 2012

One (of the very many!) neat feature of Server Core inside Windows Server 2012 is the ability to add/remote the GUI. This is a feature I wanted since Microsoft first brought out Server Core.  To add or remove the GUI in Server Core, you need to run a cmdlet from the DISM module. To Add the GUI to Server core:
Enable-WindowsOptionalFeature –Online –NoRestart `
  -Featurename ServerCore-FullServer,Server-Gui-Shell,Server-Gui-Mgmt 
Removing the GUI is equally as simple:
Disable-WindowsOptionalFeature –Online -NoRestart `  
  -Featurename ServerCore-FullServer, Server-Gui-Shell,Server-Gui-Mgmt 
I’ve written a couple of functions that do this for you – posted over on my PowerShell Scripts blog.
This is pretty cool – and it works incredibly easily. This allows you to install a server core machine, add the GUI for initial setup or subsequent troubleshooting but then easily remove it for production running. Another GREAT Server 2012 Feature enabled with PowerShell!!

Thanks to Scott R for noting a typo in this post - now fixed!

Tuesday, July 03, 2012

Even PowerShell knows the Way Forward

Came across an interesting PowerShell code fragment recently:
Nice to know PowerShell has your back.