TOPIC
about_Remote_FAQ
SHORT DESCRIPTION
Contains questions and answers about running remote commands
in Windows PowerShell.
LONG DESCRIPTION
When you work remotely, you type commands in Windows PowerShell on one
computer (known as the "local computer"), but the commands run on another
computer (known as the "remote computer"). The experience of working
remotely should be as much like working directly at the remote computer
as possible.
Note: To use Windows PowerShell remoting, the remote computer
must be configured for remoting. For more information, see
about_Remote_Requirements.
MUST BOTH COMPUTERS HAVE WINDOWS POWERSHELL INSTALLED?
Yes. To work remotely, the local and remote computers must have
Windows PowerShell, the Microsoft .NET Framework 2.0, and the Web
Services for Management (WS-Management) protocol. Any files and
other resources that are needed to execute a particular command
must be on the remote computer.
You must have permission to connect to the remote computer, permission
to run Windows PowerShell, and permission to access data stores (such as
files and folders), and the registry on the remote computer.
For more information, see about_Remote_Requirements.
HOW DOES REMOTING WORK?
When you submit a remote command, the command is transmitted across
the network to the Windows PowerShell engine on the remote computer,
and it runs in the Windows PowerShell client on the remote computer.
The command results are sent back to the local computer and appear in
the Windows PowerShell session on the local computer.
To transmit the commands and receive the output, Windows PowerShell uses
the WS-Management protocol. For information about the WS-Management
protocol, see "WS-Management Protocol" in the MSDN (Microsoft Developer
Network) library at http://go.microsoft.com/fwlink/?LinkId=144634.
IS WINDOWS POWERSHELL REMOTING SECURE?
When you connect to a remote computer, the system uses the user
name and password credentials on the local computer or the credentials
that you supply in the command to log you in to the remote computer.
The credentials and the rest of the transmission are encrypted.
To add additional protection, you can configure the remote computer
to use Secure Sockets Layer (SSL) instead of HTTP to listen for
Windows Remote Management (WinRM) requests. Then, users can use
the UseSSL parameters of the Invoke-Command, New-PSSession, and
Enter-PSSession cmdlets when establishing a connection. This option
uses the more secure HTTPS channel instead of HTTP.
DO ALL REMOTE COMMANDS REQUIRE WINDOWS POWERSHELL REMOTING?
No. Several cmdlets have a ComputerName parameter that lets
you get objects from the remote computer.
These cmdlets do not use Windows PowerShell remoting. So, you
can use them on any computer that is running Windows PowerShell,
even if the computer is not configured for Windows PowerShell
remoting or if the computer does not meet the requirements for
Windows PowerShell remoting.
These cmdlets include the following cmdlets:
Get-Process
Get-Service
Get-WinEvent
Get-EventLog
Get-WmiObject
Test-Connection
To find all the cmdlets with a ComputerName parameter, type:
get-help * -parameter ComputerName
To determine whether the ComputerName parameter of a particular cmdlet
requires Windows PowerShell remoting, see the parameter description. To
display the parameter description, type:
get-help <cmdlet-name> -parameter ComputerName
For example:
get-help get-process -parameter Computername
For all other commands, use the Invoke-Command cmdlet.
HOW DO I RUN A COMMAND ON A REMOTE COMPUTER?
To run a command on a remote computer, use the Invoke-Command cmdlet.
Enclose your command in braces ( {} ) to make it a script block. Use
the ScriptBlock parameter of Invoke-Command to specify the command.
You can use the ComputerName parameter of Invoke-Command to specify
a remote computer. Or, you can create a persistent connection to a remote
computer (a session) and then use the Session parameter of Invoke-Command
to run the command in the session.
For example, the following commands run a Get-Process command remotely.
invoke-command -computername Server01, Server02 -scriptblock {get-process}
- OR -
invoke-command -session $s -scriptblock {get-process}
To interrupt a remote command, type CTRL+C. The interruption request is
passed to the remote computer, where it terminates the remote command.
For more information about remote commands, see about_Remote and the Help
topics for the cmdlets that support remoting.
CAN I JUST "TELNET INTO" A REMOTE COMPUTER?
You can use the Enter-PSSession cmdlet to start an interactive session
with a remote computer.
At the Windows Powershell prompt, type:
Enter-PSSession <ComputerName>
The command prompt changes to show that you are connected to the remote
computer.
<ComputerName>\C:>
Now, the commands that you type run on the remote computer just as
though you typed them directly on the remote computer.
To end the interactive session, type:
Exit-PSSession
An interactive session is a persistent session that uses the WS-Management
protocol. It is not the same as using Telnet, but it provides a similar
experience.
For more information, see Enter-PSSession.
CAN I CREATE A PERSISTENT CONNECTION?
Yes. You can run remote commands by specifying the name of the
remote computer, its NetBIOS name, or its IP address. Or, you can run
remote commands by specifying a Windows PowerShell session (PSSession)
that is connected to the remote computer.
When you use the ComputerName parameter of Invoke-Command or
Enter-PSSession, Windows PowerShell establishes a temporary
connection. Windows PowerShell uses the connection to run only the current
command, and then it closes the connection. This is a very efficient
method for running a single command or several unrelated commands, even
on many remote computers.
When you use the New-PSSession cmdlet to create a PSSession, Windows
PowerShell establishes a persistent connection for the PSSession. Then,
you can run multiple commands in the PSSession, including commands that
share data.
Typically, you create a PSSession to run a series of related commands
that share data. Otherwise, the temporary connection created by the
ComputerName parameter is sufficient for most commands.
For more information about sessions, see about_PSSessions.
CAN I RUN COMMANDS ON MORE THAN ONE COMPUTER AT A TIME?
Yes. The ComputerName parameter of the Invoke-Command cmdlet accepts
multiple computer names, and the Session parameter accepts
multiple PSSessions.
When you run an Invoke-Command command, Windows PowerShell runs the
commands on all of the specified computers or in all of the specified
PSSessions.
Windows PowerShell can manage hundreds of concurrent remote connections.
However, the number of remote commands that you can send might be limited
by the resources of your computer and its capacity to establish and
maintain multiple network connections.
For more information, see the example in the Invoke-Command Help
topic.
WHERE ARE MY PROFILES?
Windows PowerShell profiles are not run automatically in remote sessions,
so the commands that the profile adds are not present in the session. In
addition, the $profile automatic variable is not populated in remote
sessions.
To run a profile in a session, use the Invoke-Command cmdlet.
For example, the following command runs the CurrentUserCurrentHost profile
from the local computer in the session in $s.
invoke-command -session $s -filepath $profile
The following command runs the CurrentUserCurrentHost profile from
the remote computer in the session in $s. Because the $profile variable
is not populated, the command uses the explicit path to the profile.
invoke-command -session $s {. "$home\Documents\WindowsPowerShell\Microsoft.PowerShell_profile.ps1"}
After running this command, the commands that the profile adds to the session
are available in $s.
You can also use a startup script in a session configuration to run a
profile in every remote session that uses the session configuration.
For more information about Windows PowerShell profiles,
see about_Profiles. For more information about session configurations,
see Register-PSSessionConfiguration.
HOW DOES THROTTLING WORK ON REMOTE COMMANDS?
To help you manage the resources on your local computer, Windows
PowerShell includes a per-command throttling feature that lets you
limit the number of concurrent remote connections that are established
for each command.
The default is 32 concurrent connections, but you can use the
ThrottleLimit parameters of the cmdlets to set a custom throttle limit
for particular commands.
When you use the throttling feature, remember that it is applied to each
command, not to the entire session or to the computer. If you are running
commands concurrently in several sessions or PSSessions, the number of
concurrent connections is the sum of the concurrent connections in all
the sessions.
To find cmdlets with a ThrottleLimit parameter, type:
get-help * -parameter ThrottleLimit
ARE THERE SYSTEM-SPECIFIC DIFFERENCES IN REMOTING?
When you run commands on multiple computers, be aware of the differences
between the remote computers, such as differences in the operating systems,
the file system structure, and the registry.
When you connect to a remote computer that is running Windows Vista or
Windows Server 2003, the default starting location is the home directory
of the current user, which is stored in the %homepath% environment variable
($env:homepath) and the Windows PowerShell $home variable. In Windows Vista,
the home directory is typically C:\Users\<UserName>. In Windows Server 2003,
the home directory is typically C:\Documents and Settings\<UserName>.
When you connect to a remote computer that is running Windows XP, the
default starting location is the home directory of the default user, which is
stored in the %homepath% environment variable ($env:homepath) for the default
user. The home directory is typically C:\Documents and Setting\Default User.
IS THE OUTPUT OF REMOTE COMMANDS DIFFERENT FROM LOCAL OUTPUT?
When you use Windows PowerShell locally, you send and receive "live" .NET
Framework objects; "live" objects are objects that are associated with
actual programs or system components. When you invoke the methods or change
the properties of live objects, the changes affect the actual program or
component. And, when the properties of a program or component change,
the properties of the object that represent them also change.
However, because most live objects cannot be transmitted over the network,
Windows PowerShell "serializes" most of the objects sent in remote commands,
that is, it converts each object into a series of XML (Constraint Language
in XML [CLiXML]) data elements for transmission.
When Windows PowerShell receives a serialized object, it converts
the XML into a deserialized object type. The deserialized object
is an accurate record of the properties of the program or component at
a previous time, but it is no longer "live", that is, it
is no longer directly associated with the component. And, the methods are
removed because they are no longer effective.
Typically, you can use deserialized objects just as you would use live
objects, but you must be aware of their limitations. Also, the objects
that are returned by the Invoke-Command cmdlet have additional properties
that help you to determine the origin of the command.
Some object types, such as DirectoryInfo objects and GUIDs, are converted
back into live objects when they are received. These objects do not need
any special handling or formatting.
For information about interpreting and formatting remote output, see
about_Remote_Output.
CAN I RUN BACKGROUND JOBS REMOTELY?
Yes. A Windows PowerShell background job is a Windows PowerShell
command that runs asynchronously without interacting with the session. When
you start a background job, the command prompt returns immediately, and you
can continue to work in the session while the job runs even if it runs for
an extended period of time.
You can start a background job even while other commands are running because
background jobs always run asynchronously in a temporary session.
You can run background jobs on a local or remote computer. By default, a
background job runs on the local computer. However, you can use the AsJob
parameter of the Invoke-Command cmdlet to run any remote command as a
background job. And, you can use Invoke-Command to run a Start-Job
command remotely.
For more information about background jobs in Windows PowerShell,
see about_Jobs and about_Remote_Jobs.
CAN I RUN WINDOWS PROGRAMS ON A REMOTE COMPUTER?
You can use Windows PowerShell remote commands to run Windows-based
programs on remote computers. For example, you can run Shutdown.exe
or Ipconfig on a remote computer.
However, you cannot use Windows PowerShell commands to open the user
interface for any program on a remote computer.
When you start a Windows program on a remote computer, the command is
not completed, and the Windows PowerShell command prompt does not return,
until the program is finished or until you press CTRL+C to interrupt the
command. For example, if you run the IpConfig program on a remote computer,
the command prompt does not return until IpConfig is completed.
If you use remote commands to start a program that has a user interface,
the program process starts, but the user interface does not appear. The
Windows PowerShell command is not completed, and the command prompt does
not return until you stop the program process or until you press CTRL+C,
which interrupts the command and stops the process.
For example, if you use a Windows PowerShell command to run Notepad on a
remote computer, the Notepad process starts on the remote computer, but
the Notepad user interface does not appear. To interrupt the command and
restore the command prompt, press CTRL+C.
CAN I LIMIT THE COMMANDS THAT USERS CAN RUN REMOTELY ON MY COMPUTER?
Yes. Every remote session must use one of the session configurations
on the remote computer. You can manage the session configurations on
your computer (and the permissions to those session configurations)
to determine who can run commands remotely on your computer and which
commands they can run.
A session configuration configures the environment for the session.
You can define the configuration by using an assembly that implements
a new configuration class or by using a script that runs in the session.
The configuration can determine the commands that are available in the
session. And, the configuration can include settings that protect the
computer, such as settings that limit the amount of data that the session
can receive remotely in a single object or command. You can also specify
a security descriptor that determines the permissions that are required
to use the configuration.
The Enable-PSRemoting cmdlet creates a default session configuration
on your computer, Microsoft.PowerShell (and Microsoft.PowerShell32 on
64-bit operating systems). Enable-PSRemoting sets the security descriptor
for the configuration to allow only members of the Administrators group
on your computer to use them.
You can use the session configuration cmdlets to edit the default
session configurations, to create new session configurations, and to change
the security descriptors of all the session configurations.
When users use the Invoke-Command, New-PSSession, or Enter-PSSession
cmdlets, they can use the ConfigurationName parameter to indicate the
session configuration that is used for the session. And, they can change
the default configuration that their sessions use by changing the value
of the $PSSessionConfigurationName preference variable in the session.
For more information about session configurations, see the Help for
the session configuration cmdlets. To find the session configuration
cmdlets, type:
get-command *pssessionconfiguration
WHAT ARE FAN-IN AND FAN OUT CONFIGURATIONS?
The most common Windows PowerShell remoting scenario involving
multiple computers is the one-to-many configuration, in which one
local computer (the administrator's computer) runs Windows PowerShell
commands on numerous remote computers. This is known as the
"fan-out" scenario.
However, in some enterprises, the configuration is many-to-one, where
many client computers connect to a single remote computer that is
running Windows PowerShell, such as a file server or a kiosk.
This is known as the "fan-in" configuration.
Windows PowerShell remoting supports both fan-out and fan-in
configurations.
For the fan-out configuration, Windows PowerShell uses the Web Services for
Management (WS-Management) protocol and the WinRM service that supports the
Microsoft implementation of WS-Management. When a local computer connects to
a remote computer, WS-Management establishes a connection and uses a plug-in
for Windows PowerShell to start the Windows PowerShell host process
(Wsmprovhost.exe) on the remote computer. The user can specify an alternate
port, an alternate session configuration, and other features to customize
the remote connection.
To support the "fan-in" configuration, Windows PowerShell uses Internet
Information Services (IIS) to host WS-Management, to load the Windows
PowerShell plug-in, and to start Windows PowerShell. In this scenario,
instead of starting each Windows PowerShell session in a separate process,
all Windows PowerShell sessions run in the same host process.
IIS hosting and fan-in remote management is not supported in Windows XP or
in Windows Server 2003.
In a fan-in configuration, the user can specify a connection URI and an
HTTP endpoint, including the transport, computer name, port, and application
name. IIS forwards all the requests with a specified application name to the
application. The default is WS-Management, which can host Windows
PowerShell.
You can also specify an authentication mechanism and prohibit or allow
redirection from HTTP and HTTPS endpoints.
CAN I TEST REMOTING ON A SINGLE COMPUTER (NOT IN A DOMAIN)?
Yes. Windows PowerShell remoting is available even when the local
computer is not in a domain. You can use the remoting features to
connect to sessions and to create sessions on the same computer. The
features work the same as they do when you connect to a remote computer.
To run remote commands on a computer in a workgroup, change the
following Windows settings on the computer.
Caution: These settings affect all users on the system and they can
make the system more vulnerable to a malicious attack. Use
caution when making these changes.
-- Windows XP with SP2:
Use Local Security Settings (Secpol.msc) to change the setting of the
"Network Access: Sharing and security model for local accounts" policy
in Security Settings\Local Policies\Security Options to "Classic".
-- Windows Vista:
Create the following registry entry, and then set its value to 1:
LocalAccountTokenFilterPolicy in
HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System
You can use the following Windows PowerShell command to add this entry:
new-itemproperty `
–path HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System `
–name LocalAccountTokenFilterPolicy –propertyType DWord –value 1
-- Windows 2003:
No changes are needed because the default setting of the
"Network Access: Sharing and security model for local accounts" policy
is "Classic". Verify the setting in case it has changed.
CAN I RUN REMOTE COMMANDS ON A COMPUTER IN ANOTHER DOMAIN?
Yes. Typically, the commands run without error, although you might need
to use the Credential parameter of the Invoke-Command, New-PSSession,
or Enter-PSSession cmdlets to provide the credentials of a member of the
Administrators group on the remote computer. This is sometimes required
even when the current user is a member of the Administrators group on the
local and remote computers.
However, if the remote computer is not in a domain that the local computer
trusts, the remote computer might not be able to authenticate the user's
credentials.
To enable authentication, use the following command to add the remote
computer to the list of trusted hosts for the local computer in WinRM.
Type the command at the Windows PowerShell prompt.
set-item WSMan:\localhost\Client\TrustedHosts -value <Remote-computer-name>
For example, to add the Server01 computer to the list of trusted hosts
on the local computer, type the following command at the Windows
PowerShell prompt:
set-item WSMan:\localhost\Client\TrustedHosts -value Server01
SEE ALSO
about_Remote
about_Profiles
about_PSSessions
about_Remote_Jobs
Invoke-Command
New-PSSession
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