TOPIC
about_Remote_Jobs
SHORT DESCRIPTION
Describes how to run background jobs on remote computers.
DETAILED DESCRIPTION
A background job is a command that runs asynchronously without interacting
with the current session. The command prompt returns immediately, and you
can continue to use the session while the job runs.
By default, background jobs run on the local computer. However, you can
use several different procedures to run background jobs on remote
computers.
This topic explains how to run a background job on a remote computer. For
information about how to run background jobs on a local computer, see
about_Jobs. For more information about background jobs, see
about_Job_Details.
REMOTE BACKGROUND JOBS
You can run background jobs on remote computers by using three different
methods.
-- Start an interactive session with a remote computer, and start a job
in the interactive session. The procedures are the same as running a
local job, although all actions are performed on the remote computer.
-- Run a background job on a remote computer that returns its results to
the local computer. Use this method when you want to collect the
results of background jobs and maintain them in a central location on
the local computer.
-- Run a background job on a remote computer that maintains its results
on the remote computer. Use this method when the job data is more
securely maintained on the originating computer.
START A BACKGROUND JOB IN AN INTERACTIVE SESSION
You can start an interactive session with a remote computer and then
start a background job during the interactive session. For more
information about interactive sessions, see about_Remote, and
see Enter-PSSession.
The procedure for starting a background job in an interactive session is
almost identical to the procedure for starting a background job on the
local computer. However, all of the operations occur on the remote
computer, not the local computer.
STEP 1: ENTER-PSSESSION
Use the Enter-PSSession cmdlet to start an interactive session with a
remote computer. You can use the ComputerName parameter of Enter-PSSession
to establish a temporary connection for the interactive session. Or, you
can use the Session parameter to run the interactive session in a Windows
PowerShell session (PSSession).
The following command starts an interactive session on the Server01
computer.
C:\PS> Enter-PSSession -computername Server01
The command prompt changes to show that you are now connected to the
Server01 computer.
Server01\C:>
STEP 2: START-JOB
To start a background job in the session, use the Start-Job cmdlet.
The following command runs a background job that gets the events in the
Windows PowerShell event log on the Server01 computer. The Start-Job
cmdlet returns an object that represents the job.
This command saves the job object in the $job variable.
Server01\C:> $job = start-job -scriptblock {get-eventlog "Windows PowerShell"}
While the job runs, you can use the interactive session to run other
commands, including other background jobs. However, you must keep the
interactive session open until the job is completed. If you end the
session, the job is interrupted, and the results are lost.
STEP 3: GET-JOB
To find out if the job is complete, display the value of the $job variable,
or use the Get-Job cmdlet to get the job. The following command uses the
Get-Job cmdlet to display the job.
Server01\C:> get-job $job
SessionId Name State HasMoreData Location Command
--------- ---- ----- ----------- -------- -------
1 Job1 Complete True localhost get-eventlog "Windows PowerShell"
The Get-Job output shows that job is running on the "localhost" computer
because the job was started on and is running on the same computer (in
this case, Server01).
STEP 4: RECEIVE-JOB
To get the results of the job, use the Receive-Job cmdlet. You can display
the results in the interactive session or save them to a file on the remote
computer. The following command gets the results of the job in the $job
variable. The command uses the redirection operator (>) to save the results
of the job in the PsLog.txt file on the Server01 computer.
Server01\C:> receive-job $job > c:\logs\PsLog.txt
STEP 5: EXIT-PSSESSION
To end the interactive session, use the Exit-PSSession cmdlet. The command
prompt changes to show that you are back in the original session on the
local computer.
Server01\C:> Exit-PSSession
C:\PS>
STEP 6: INVOKE-COMMAND: GET CONTENT
To view the contents of the PsLog.txt file on the Server01 computer at any
time, start another interactive session, or run a remote command. This type
of command is best run in a PSSession (a persistent connection) in case you
want to use several commands to investigate and manage the data in the
PsLog.txt file. For more information about PSSessions,
see about_PSSessions.
The following commands use the New-PSSession cmdlet to create a PSSession
that is connected to the Server01 computer, and they use the Invoke-Command
cmdlet to run a Get-Content command in the PSSession to view the contents
of the file.
C:\PS> $s = new-pssession -computername Server01
C:\PS> invoke-command -session $s -scriptblock {get-content c:\logs\pslog.txt}
START A REMOTE JOB THAT RETURNS THE RESULTS TO THE LOCAL COMPUTER (ASJOB)
To start a background job on a remote computer that returns the command
results to the local computer, use the AsJob parameter of a cmdlet such
as the Invoke-Command cmdlet.
When you use the AsJob parameter, the job object is actually created on
the local computer even though the job runs on the remote computer. When
the job is completed, the results are returned to the local computer.
You can use the cmdlets that contain the Job noun (the Job cmdlets) to
manage any job created by any cmdlet. Many of the cmdlets that have
AsJob parameters do not use Windows PowerShell remoting, so
you can use them even on computers that are not configured for
remoting and that do not meet the requirements for remoting.
STEP 1: INVOKE-COMMAND -ASJOB
The following command uses the AsJob parameter of Invoke-Command to start
a background job on the Server01 computer. The job runs a Get-Eventlog
command that gets the events in the System log. You can use the JobName
parameter to assign a display name to the job.
invoke-command -computername Server01 -scriptblock {get-eventlog system} -asjob
The results of the command resemble the following sample output.
SessionId Name State HasMoreData Location Command
--------- ---- ----- ----------- -------- -------
1 Job1 Running True Server01 get-eventlog system
When the AsJob parameter is used, Invoke-Command returns the same type of
job object that Start-Job returns. You can save the job object in a
variable, or you can use a Get-Job command to get the job.
Note that the value of the Location property shows that the job ran on the
Server01 computer.
STEP 2: GET-JOB
To manage a job started by using the AsJob parameter of the Invoke-Command
cmdlet, use the Job cmdlets. Because the job object that represents the
remote job is on the local computer, you do not need to run remote commands
to manage the job.
To determine whether the job is complete, use a Get-Job command. The
following command gets all of the jobs that were started in the current
session.
get-job
Because the remote job was started in the current session, a local Get-Job
command gets the job. The State property of the job object shows that the
command was completed successfully.
SessionId Name State HasMoreData Location Command
--------- ---- ----- ----------- -------- -------
1 Job1 Completed True Server01 get-eventlog system
STEP 3: RECEIVE-JOB
To get the results of the job, use the Receive-Job cmdlet. Because the job
results are automatically returned to the computer where the job object
resides, you can get the results with a local Receive-Job command.
The following command uses the Receive-Job cmdlet to get the results of the
job. It uses the session ID to identify the job. This command saves the job
results in the $results variable. You can also redirect the results to a
file.
$results = receive-job -id 1
START A REMOTE JOB THAT KEEPS THE RESULTS ON THE REMOTE COMPUTER
To start a background job on a remote computer that keeps the command
results on the remote computer, use the Invoke-Command cmdlet to run
a Start-Job command on a remote computer. You can use this method to run
background jobs on multiple computers.
When you run a Start-Job command remotely, the job object is created on the
remote computer, and the job results are maintained on the remote computer.
From the perspective of the job, all operations are local. You are just
running commands remotely to manage a local job on the remote computer.
STEP 1: INVOKE-COMMAND START-JOB
Use the Invoke-Command cmdlet to run a Start-Job command on a remote
computer.
This command requires a PSSession (a persistent connection). If you use
the ComputerName parameter of Invoke-Command to establish a temporary
connection, the Invoke-Command command is considered to be complete when
the job object is returned. As a result, the temporary connection is
closed, and the job is canceled.
The following command uses the New-PSSession cmdlet to create a PSSession
that is connected to the Server01 computer. The command saves the PSSession
in the $s variable.
$s = new-pssession -computername Server01
The next command uses the Invoke-Command cmdlet to run a Start-Job command
in the PSSession. The Start-Job command and the Get-Eventlog command are
enclosed in braces.
invoke-command -session $s -scriptblock {start-job -scriptblock {get-eventlog system}}
The results resemble the following sample output.
Id Name State HasMoreData Location Command
-- ---- ----- ----------- -------- -------
2 Job2 Running True Localhost get-eventlog system
When you run a Start-Job command remotely, Invoke-Command returns the same
type of job object that Start-Job returns. You can save the job object in
a variable, or you can use a Get-Job command to get the job.
Note that the value of the Location property shows that the job ran on the
local computer, known as "LocalHost", even though the job ran on the
Server01 computer. Because the job object is created on the Server01
computer and the job runs on the same computer, it is considered to
be a local background job.
STEP 2: INVOKE-COMMAND GET-JOB
To manage a remote background job, use the Job cmdlets. Because the job
object is on the remote computer, you need to run remote commands to get,
stop, wait for, or retrieve the job results.
To see if the job is complete, use an Invoke-Command command to run a
Get-Job command in the PSSession that is connected to the Server01
computer.
invoke-command -session $s -scriptblock {get-job}
The command returns a job object. The State property of the job object
shows that the command was completed successfully.
SessionId Name State HasMoreData Location Command
--------- ---- ----- ----------- -------- -------
2 Job2 Completed True LocalHost get-eventlog system
STEP 3: INVOKE-COMMAND RECEIVE-JOB
To get the results of the job, use the Invoke-Command cmdlet to run a
Receive-Job command in the PSSession that is connected to the Server01
computer.
The following command uses the Receive-Job cmdlet to get the results of
the job. It uses the session ID to identify the job. This command saves
the job results in the $results variable. It uses the Keep parameter of
Receive-Job to keep the result in the job cache on the remote
computer.
$results = invoke-command -session $s -scriptblock {receive-job -sessionid 2 -keep}
You can also redirect the results to a file on the local or remote
computer. The following command uses a redirection operator to save the
results in a file on the Server01 computer.
invoke-command -session $s -command {receive-job -sessionid 2 > c:\logs\pslog.txt}
SEE ALSO
about_Jobs
about_Job_Details
about_Remote
Invoke-Command
Start-Job
Get-Job
Wait-Job
Stop-Job
Remove-Job
New-PSSession
Enter-PSSession
Exit-PSSession