Query repository classes from remote computers by using CIMSession objects
A Common Information Model (CIM) session is a persistent configuration object that's used when creating a connection to a remote computer. The connection uses WS-MAN by default, but you can specify the DCOM protocol. After a session is created, you can use it to process multiple queries for that computer. This simplifies connectivity because all of the configuration options are contained in the session. A CIM session also allows you to specify connectivity options that aren't available for an ad hoc connection.
Creating session objects
When you create a session, you should store it in a variable to reference it later. The basic syntax to create a session and store it in a variable is:
$s = New-CimSession -ComputerName LON-DC1
You can create multiple sessions at the same time:
$sessions = New-CimSession -ComputerName LON-CL1,LON-DC1
When you create a session, PowerShell doesn't establish the connection immediately. When a cmdlet uses the CIM session, PowerShell connects to the specified computer, and then, when the cmdlet finishes, PowerShell terminates the connection.
Note
In some cases, it might be beneficial to use PowerShell remoting instead of CIM sessions for remote connectivity. PowerShell remoting opens a connection to the remote computer and keeps it open until explicitly closed. If you're running multiple queries against a computer, this might improve performance.
Using sessions
After you've stored the session in a variable, you reference it with CIM cmdlets by using the -CimSession parameter. The following example uses a variable that contains multiple sessions:
Get-CimInstance -CimSession $sessions -ClassName Win32_OperatingSystem
Remember that sessions are designed to work best in a domain environment, between computers in the same domain or in trusting domains. If you have to create a session to a nondomain computer or to a computer in an untrusted domain, you'll need to do additional configuration. You'll learn more about that configuration in Module 8, “Administering remote computers with Windows PowerShell.”
Note
The help information for some cmdlets such as Get-SmbShare states that they support a -CimSession parameter. Those commands use CIM internally. When you use those commands to query a remote computer, you can provide a CIM session object to the -CimSession parameter to connect by using an existing session.
Configuring session options
A session option object allows you to specify many settings for a session. When you create a new session, you specify the session option object to configure the session. The following example creates a session by using DCOM instead of WS-MAN:
$opt = New-CimSessionOption -Protocol Dcom
$DcomSession = New-CimSession -ComputerName LON-DC1 -SessionOption $opt
Get-CimInstance -ClassName Win32_BIOS -CimSession $DcomSession
The first line in the preceding code creates a session option object that specifies that the DCOM protocol should be used for connectivity. The second line creates a new session by using that session option object and stores it in a variable. The final line uses the session to query the remote computer defined in the session and return the requested information.
Removing sessions
After you create a session, it remains in memory and available for use until the instance of PowerShell is closed. You can manually remove sessions by using the Remove-CimSession cmdlet. The following example removes one or more sessions contained in a variable:
$sessions | Remove-CimSession
To remove the sessions for a specific remote computer, you can query the sessions for that computer and then remove them, as the following example depicts:
Get-CimSession -ComputerName LON-DC1 | Remove-CimSession
To remove all sessions, run the following command:
Get-CimSession | Remove-CimSession