PSMonday #16: Monday, August 15, 2016

Topic: PowerShell Remoting Continued V

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.

I think back on the last few weeks and there’s a few things we haven’t covered. Let’s say we have four servers and we want to run the same command on each one. We know we can use Invoke-Command and supply four names as the value to the -ComputerName parameter. Jump back to PSMonday #11 on July 11, 2016, for an example.

In today’s PSMonday, we’ll see how to do this another way. We’ll start by creating four PS Remoting sessions. Each session object will hold the session information for an opened session with a remote computer. Displaying the value stored in the variable $Session includes the ConfigurationName property. In the below example, you can see it’s the default endpoint — Microsoft.PowerShell — we discussed last week.

$Session = New-PSSession -Computer DC01,DC02,DC03,DC04
$Session

Id Name           ComputerName    State         ConfigurationName     Availability
-- ----           ------------    -----         -----------------     ------------
4 Session4        DC04            Opened        Microsoft.PowerShell     Available
3 Session3        DC03            Opened        Microsoft.PowerShell     Available
2 Session2        DC02            Opened        Microsoft.PowerShell     Available
1 Session1        DC01            Opened        Microsoft.PowerShell     Available

With these sessions stored in the variable $Session, we can use Invoke-Command and the -Session parameter to run commands against each computer. Here’s a slightly modify version from that previous PSMonday.

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

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

One benefit of using sessions is speed while running the commands against the remote computer. It’ll be marginable, until you have a good number of computers as a part of your session variable. The reason there’s a boost in speed is because you already have currently existing sessions to use. Invoke-Command doesn’t have to create sessions, and then destroy them, when it’s done. I should note that it still takes time to create the sessions prior to using them.

Another benefit is when you need to run multiple commands against the same computers, but don’t want to do it at the same time. You can connect and collect some data and then connect again later without the need to create a new connection. Think about it, you can create a variable in the session and it will continue to exist. This means your second Invoke-Command can use the variable you created with the first Invoke-Command, command. See the below example.

$Session = New-PSSession -ComputerName DC05
Invoke-Command -Session $Session -ScriptBlock {$Var = $env:COMPUTERNAME}
Start-Sleep -Seconds 5
Invoke-Command -Session $Session -ScriptBlock {$Var}

DC05

I think we may be done with PowerShell Remoting. We’ll see.

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