Topic: PowerShell Remoting

Notice: This post is a part of the PowerShell Monday series — a group of quick and easy to read mini lessons that briefly cover beginning and intermediate PowerShell topics. As a PowerShell enthusiast, this seemed like a beneficial way to ensure those around me at work were consistently learning new things about Windows PowerShell. At some point, I decided I would share these posts here, as well. Here’s the PowerShell Monday Table of Contents.

When Windows PowerShell 2.0 was released, it came with some welcoming new features. One of the biggest, was PowerShell Remoting. Let’s discuss PS Remoting in regard to two cmdlets: Enter-PSSession and Invoke-Command.

Enter-PSSession allows for a fully interactive PowerShell remoting session. It’s as though you’re sitting at the PowerShell prompt on the remote computer, with the ability to interactively enter commands and immediately see those results. Using Enter-PSSession is considered one-to-one PS Remoting. Here’s an example of using Enter-PSSession with the explanation beneath that.

Enter-PSSession -ComputerName DC01

[DC01]: PS C:\Users\tommymaynard\Documents> Set-Location -Path \
[DC01]: PS C:\> "**** $env:COMPUTERNAME ****"
**** DC01 ****
[DC01]: PS C:\> Exit-PSSession
PS C:>

Let’s discuss each of the above lines in this example. The first line is the command we used to connect to the DC01 computer. Once connected, we move to the root of the drive using the Set-Location cmdlet. This isn’t a requirement, but a shorter path will offer more area in which to type. Then, we instructed the computer to echo four asterisks, a space, the value stored in the computer name environmental variable, another space, and another four asterisks. This is proof, outside the computer’s name in square brackets at the left of the prompt, that we really are on the remote computer. Finally, we run Exit-PSSession to exit the PS Remoting session on DC01, and return to the local computer.

Invoke-Command allows you to send a command to a remote computer, have it run, and have the results sent back and displayed in your console, on the local computer. While you can do this against a single computer, this is considered one-to-many PS Remoting, and you’ll see why momentarily. The next example does the same thing as we did in the above, Enter-PSSession example.

Invoke-Command -ComputerName DC01 -ScriptBlock {"**** $env:COMPUTERNAME ****"}

**** DC01 ****

Invoke-Command has some great features: One, it can run against multiple computers, as you may have already picked up on, or simply knew, and two, it can do this at the same time. Now, there is a built-in limitation of 32 computers that it will run against at once; however, that can be changed with the -ThrottleLimit parameter and a parameter value of something other than 32.

Invoke-Command -ComputerName DC01,DC02,DC03,DC04 -ScriptBlock {"**** $env:COMPUTERNAME ****"}

**** DC01 ****
**** DC04 ****
**** DC02 ****
**** DC03 ****

Because this last example ran against multiple computers at once, you won’t always get the results back in the order you might expect. This is because it’s up to how quickly each computer can be reached, how quickly each command(s) can be run, and how quickly each computer can send the results back to the local computer. This command above could’ve been written as is shown below.

Invoke-Command -ComputerName (Get-ADDomainController -Filter *) -ScriptBlock {"**** $env:COMPUTERNAME ****"}

**** DC01 ****
**** DC02 ****
**** DC04 ****
**** DC03 ****

Start to consider all those times you use Remote Desktop. Are there times you can skip that somewhat lengthy process, and instead return the results you’re after, using PowerShell Remoting?