TOPIC
about_PSSessions
SHORT DESCRIPTION
Describes Windows PowerShell sessions (PSSessions) and explains how to
establish a persistent connection to a remote computer.
LONG DESCRIPTION
To run Windows PowerShell commands on a remote computer, you can use the
ComputerName parameter of a cmdlet, or you can create a Windows PowerShell
session (PSSession) and run commands in the PSSession.
When you create a PSSession, Windows PowerShell establishes a persistent
connection to the remote computer. Use a PSSession to run a series of
related commands on a remote computer. Commands that run in the same
PSSession can share data, such as the values of variables, aliases, and
functions.
You can also create a PSSession on the local computer and run commands
in it. A local PSSession uses the Windows PowerShell remoting
infrastructure to create and maintain the PSSession.
This topic explains how to create, use, get, and delete PSSessions.
For more advanced information, see about_PSSession_Details.
Note: PSSessions use the Windows PowerShell remoting infrastructure.
To use PSSessions, the local and remote computers must be configured
for remoting. For more information, see about_Remote_Requirements.
In Windows Vista and later versions of Windows, to create a
PSSession on a local computer, you must start Windows PowerShell
with the "Run as administrator" option.
WHAT IS A SESSION?
A session is an environment in which Windows PowerShell runs.
Each time you start Windows PowerShell, a session is created for you, and
you can run commands in the session. You can also add items to your session,
such as modules and snap-ins, and you can create items, such as variables,
functions, and aliases. These items exist only in the session and are
deleted when the session ends.
You can also create additional sessions, known as "Windows PowerShell
sessions" or "PSSessions," on the local computer or on a remote computer.
Like the default session, you can run commands in a PSSession and add and
create items.
However, unlike the session that starts automatically, you can control the
PSSessions that you create. You can get, create, configure, and remove them,
and you can run multiple commands in the same PSSession. The PSSession
remains open and available until you delete it from your session.
Typically, you create a PSSession to run a series of related commands on a
remote computer. When you create a PSSession on a remote computer,
Windows PowerShell establishes a persistent connection to the remote
computer to support the session.
If you use the computerName parameter of the Invoke-Command or
Enter-PSSession cmdlet to run a remote command or to start an interactive
session, Windows PowerShell creates a temporary session on the remote
computer and closes the session as soon as the command is complete or as
soon as the interactive session ends. You cannot control these temporary
sessions, and you cannot use them for more than a single command or a
single interactive session.
In Windows PowerShell, the "current session" is the session that you are
working in. The "current session" can refer to any session, including a
temporary session or a PSSession.
WHY USE A PSSESSION?
Use a PSSession when you need a persistent connection to a remote computer.
With a PSSession, you can run a series of commands that share data, such as
the value of variables, the contents of a function, or the definition of an
alias.
You can run remote commands without creating a PSSession. Use the
ComputerName parameter of remote-enabled cmdlets to run a single command
or a series of unrelated commands on one or many computers.
When you use the ComputerName parameter of Invoke-Expression or
Enter-PSSession, Windows PowerShell establishes a temporary connection to
the remote computer and then closes the connection as soon as the command
is complete. Any data elements that you create are lost when the connection
is closed.
Other cmdlets that have a ComputerName parameter, such as Get-Eventlog and
Get-WmiObject, use different remoting technologies to gather data. None
create a persistent connection like a PSSession.
HOW TO CREATE A PSSESSION
To create a PSSession, use the New-PSSession cmdlet. To create the
PSSession on a remote computer, use the ComputerName parameter of the
New-PSSession cmdlet.
For example, the following command creates a new PSSession on the
Server01 computer.
new-pssession -computername Server01
When you submit the command, New-PSSession creates the PSSession and
returns an object that represents the PSSession. You can save the object in
a variable when you create the PSSession, or you can use a Get-PSSession
command to get the PSSession at a later time.
For example, the following command creates a new PSSession on the Server01
computer and saves the resulting object in the $ps variable.
$ps = new-pssession -computername Server01
HOW TO CREATE PSSESSIONS ON MULTIPLE COMPUTERS
To create PSSessions on multiple computers, use the ComputerName parameter
of the New-PSSession cmdlet. Type the names of the remote computers in a
comma-separated list.
For example, to create PSSessions on the Server01, Server02, and Server03
computers, type:
new-PSSession -computername Server01, Server02, Server03
New-PSSession creates one PSSession on each of the remote computers.
HOW TO GET PSSESSIONS
To get the PSSessions that were created in your current session, use the
Get-PSSession cmdlet. Get-PSSession returns the same type of object that
New-PSSession returns.
The following command gets all the PSSessions that were created in the
current session.
get-PSSession
The default display of the PSSessions shows their ID and a default display
name. You can assign an alternate display name when you create the
session.
Id Name ComputerName State ConfigurationName
--- ---- ------------ ----- ---------------------
1 Session1 Server01 Opened Microsoft.PowerShell
2 Session2 Server02 Opened Microsoft.PowerShell
3 Session3 Server03 Opened Microsoft.PowerShell
You can also save the PSSessions in a variable. The following command gets
the PSSessions and saves them in the $ps123 variable.
$ps123 = get-PSSession
When using the PSSession cmdlets, you can refer to a PSSession by its ID, by
its name, or by its instance ID (a GUID). The following command gets a
PSSession by its ID and saves it in the $ps01 variable.
$ps01 = get-PSSession -id 1
Get-PSSession gets only the PSSessions that were created in the current
session. It does not get PSSessions that were created in other sessions or
on other computers, even if the sessions are connected to and are running
commands on the local computer.
HOW TO RUN COMMANDS IN A PSSESSION
To run a command in one or more PSSessions, use the Invoke-Command cmdlet.
Use the Session parameter to specify the PSSessions and the ScriptBlock
parameter to specify the command.
For example, to run a Get-ChildItem ("dir") command in each of the three
PSSessions saved in the $ps123 variable, type:
invoke-command -session $ps123 -scriptblock {get-childitem}
HOW TO DELETE PSSESSIONS
When you are finished with the PSSession, use the Remove-PSSession cmdlet
to delete the PSSession and to release the resources that it was using.
remove-PSSession -session $ps
- or -
remove-PSSession -id 1
If you do not delete the PSSession, the PSSession remains open and
available for use until you close the current session or until you exit
Windows PowerShell.
You can also use the TimeOut parameter of New-PSSession to set an
expiration time for an idle PSSession. For more information,
see new-PSSession.
THE PSSESSION CMDLETS
Cmdlet Description
----------------- ------------------------------------------------------
New-PSSession Creates a new PSSession on a local or remote computer.
Get-PSSession Gets the PSSessions in the current session.
Remove-PSSession Deletes the PSSessions in the current session.
Enter-PSSession Starts an interactive session.
Exit-PSSession Ends an interactive session.
For a list of PSSession cmdlets, type:
get-help *-PSSession
FOR MORE INFORMATION
For more information about PSSessions, see about_PSSession_Details.
SEE ALSO
about_Remote
about_Remote_Requirements
New-PSSession
Get-PSSession
Remove-PSSession
Enter-PSSession
Exit-PSSession
Invoke-Command