Coral: cron srvstart utility: Difference between revisions

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<span style="margin-bottom:5px;font-size:25px;color: #31799F;">CRON - SrvStart utility tutorial</span>
<span style="margin-bottom:5px;font-size:25px;color: #31799F;">CRON - SrvStart utility tutorial</span>


This short tutorial covers the SrvStart utility written by Nick Rozanski. It allows you to run a script as a service!  
This short tutorial covers using the SrvStart utility written by Nick Rozanski. It allows you to run a script as a service!  


'''What is a Service?'''<br />
'''What is a Service?'''<br />
A Windows Service is automatically started when your PC starts. Services automatically recover from program crashes and Standby or hibernation modes. Installing software as a Service requires Administrator permissions.
A Windows Service is automatically started when your PC starts. Services automatically recover from program crashes and Standby or Hibernation modes. Installing software as a service requires Administrator permissions.




'''Complexity'''<br />
'''Complexity'''<br />
Programs (application) designed to run as a service contain code that interface to the Windows service manager. Running a script as a service requires additional code that allows it to access the Windows service manager. This code registers your script allowing it to be run as a service in addition it must provide responses to command requests from the service manager and have the ability to provide your scripts status.
An application program designed to run as a service contains code that interfaces to the Windows service manager. Running a script as a service requires additional code that allows it to access the Windows service manager. This code registers your script, allowing it to be run as a service. In addition it must provide responses to command requests from the service manager and have the ability to provide your script's status.


Not a trivial exercise however this complexity is hidden when using SrvStart.  
It's not a trivial exercise, but this complexity is hidden when using SrvStart.  




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* svc.exe
* svc.exe


We are interest only in files '''srvstart.exe''', '''srvstart.dll''' and '''logger.dll'''<br />
We are only interested in files '''srvstart.exe''', '''srvstart.dll''' and '''logger.dll'''<br />
For this tutorial create a new folder c:\'''service_test''' and copy the above three files into it.
For this tutorial, create a new folder c:\'''service_test''' and copy the above three files into it.




'''Note 1:'''<br />
'''Note 1:'''<br />
The documentation states copy files srvstart.exe, srvstart.dll, logger.dll and msvcrt.dll to C:\WINDOWS\system32 (system path). For XP onwards msvcrt.dll is already installed on a system path. Other three files need not be installed on a system path see below.
The documentation says to copy files srvstart.exe, srvstart.dll, logger.dll and msvcrt.dll to C:\WINDOWS\system32 (system path). For XP onwards msvcrt.dll is already installed on a system path. The other three files do not need to be installed on a system path; see below.
We are going to run srvstart.exe from its installation folder. This allows it to be portable by not installing anything on a host PC (assumes running from memory stick).
We are going to run srvstart.exe from its installation folder. This allows it to be portable by not installing anything on a host PC (assumes running from memory stick).


'''Note 2:'''<br />
'''Note 2:'''<br />
When installing a service it does write to the registry hence remember to stop and uninstall the service you create especially if running from a memory stick.  
Notwithstanding the above, when installing a service, it does write to the registry, so you must remember to stop and uninstall the service you create if it resides on an external drive or a memory stick.  


'''''[[#top | Top]]'''''
==Script to run==
==Script to run==
For this tutorial we require a script to run. Create a new text document named '''my_script.vbs''' with the following content:
For this tutorial we require a script to run. Create a new text document named '''my_script.vbs''' with the following content:
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</pre>
</pre>
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This is an annoying VBScript it produces beeps when run.
This is an annoying VBScript which just produces beeps when it runs.
 


Double click on my_script.vbs and confirm it produces two beeps.
Double click on my_script.vbs and confirm that it produces two beeps.
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===Limitation===
===Limitation===
An application to be run as a service must have one of the following file extensions .exe, .com or .bat The script we want to run has an extension .vbs hence cannot be run directly.
An application to be run as a service must have one of the following file extensions: .exe, .com or .bat. The script we want to run has an extension of .vbs so it cannot be run directly.


At first this looks very restrictive however a batch file will run any application.
At first this looks very restrictive, however a batch file will run any application.
To run our script as a service create a batch file named my_script.bat with the following content:
To run our script as a service, create a batch file named my_script.bat with the following content:


{|
{|
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</pre>
</pre>
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'''start''' Runs our vb script and closes. It does not wait for our vb script to finish<br />
'''start''' Runs our vb script and closes. It does not wait for our vb script to finish.<br />
Double click on my_script.bat and confirm it produces two beeps.
Double click on my_script.bat and confirm it produces two beeps.
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'''Note 1:''' Running my_script.bat a command window opens for a short time. When run as a service this is hidden.<br />
'''Note 1:''' Running my_script.bat a command window opens for a short time. When run as a service this is hidden.<br />


'''Note 2:''' Removing the "start" keyword our vb script runs and the command window remains open until vb script finishes. Again when run as a service this is hidden.
'''Note 2:''' Removing the "start" keyword, our vb script runs and the command window remains open until vb script finishes. Again, when run as a service, this is hidden.




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==SrvStart configuration file==
==SrvStart configuration file==
To create our application (script) service SrvStart requires a configuration file.
To create our application (script) service SrvStart requires a configuration file.
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==Control_batch_files==
==Control_batch_files==
We are now ready to install and run our service this can be done using a command prompt and issuing the appropriate commands.
We are now ready to install and run our service. This can be done using a command prompt and issuing the appropriate commands.
I prefer to put these commands into separate batch files as follows:
I prefer to put these commands into separate batch files as follows:


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==Test - Perceived problems==
==Test - Perceived problems==
{|
{|
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Run '''z_service_start.bat'''
Run '''z_service_start.bat'''
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Confirm two bleeps are produced. Note the following messages
Confirm two beeps are produced. Note the following messages:
* The z_test service is starting.
* The z_test service is starting.
* The z_test service could not be started.
* The z_test service could not be started.
* The service did not report an error.
* The service did not report an error.
* More help is available by typing NET HELPMSG 3534.
* More help is available by typing NET HELPMSG 3534.
With the confirmation of two beeps our script was successfully run. Reason for '''could not be started message'''; the batch file closes immediately when run. Srvstart regularly checks running status of an application it started, it immediately sees the script no longer running and reports back to the service control it could not be started.
With the confirmation of two beeps, our script was successfully run. The reason for '''could not be started message'''; the batch file closes immediately when run. Srvstart regularly checks the running status of an application it started, it immediately sees the script is no longer running and reports back to the service control that it could not be started.
The service did not report an error because it’s not an error.
The service did not report an error because it’s not an error.
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* The z_test service is not started.
* The z_test service is not started.
* More help is available by typing NET HELPMSG 3521.
* More help is available by typing NET HELPMSG 3521.
The batch file is not running hence the service as reported is not running see above.
The batch file is not running, hence the service is reported as not running; see above.
Above is not a problem its the way we want to run our scrip.
The above is not a problem; it's the way we want to run our script.
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Confirms correct operation
Confirms correct operation
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'''Note:''' The above results may be a little confusing, remember our VBScript does not run continuously its a run once program. Its purpose is to familiarise yourself with the Srvstart program.
'''Note:''' The above results may be a little confusing. Rremember our VBScript does not run continuously; it's a run-once program. Its purpose is to familiarise yourself with the SrvStart program.


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==Service Status==
==Service Status==
With the service created, it will now appear in the Windows Services list and can be configured like any other Windows Service.
With the service created, it will now appear in the Windows Services list and can be configured like any other Windows Service.
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* It is set to Manual startup.
* It is set to Manual startup.
* It starts using LocalSystem and has no dependencies.
* It starts using LocalSystem and has no dependencies.
* If cannot interact with the desktop.
* It cannot interact with the desktop.
   
   
===Manual startup===
===Manual startup===
Service start type specifies the services behavior after reboot:
The service start type specifies the service's behavior after reboot:


* Auto - Automatically start after a re-boot
* Auto - Automatically start after a re-boot
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* Disabled - Deactivated
* Disabled - Deactivated


We want our script to start when the PC is powered up. Either change the Manual state to Auto using service manger.
We want our script to start when the PC is powered up. Either change the Manual state to Auto using service manger, or
Alternatively use a script to set the service state. Create a new file named '''start_automatic.vbs''' with the following content:
use a script to set the service state. Create a new file named '''start_automatic.vbs''' with the following content:


<pre>
<pre>
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For testing this script starts our service and changes it to Automatic.
For testing, this script starts our service and changes it to Automatic.


<pre>
<pre>
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</pre>
</pre>


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==Simulating service program crash==
==Simulating service program crash==
Our batch file is ideal for simulating a service program crash and demonstrating recovery. The batch file only runs once (simulating a program crash), srvstat can be set to automatically restart the program using directive '''auto_restart=y''', setting '''restart_interval=seconds''' will pause before starting.
Our batch file is ideal for simulating a service program crash and demonstrating recovery. The batch file only runs once (simulating a program crash), srvstat can be set to automatically restart the program using directive '''auto_restart=y''', setting '''restart_interval=seconds''' will pause before starting.
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'''Note 1:''' auto_restart will restart the service program if it exits for any reason. If restart_interval is defined, then before restarting, SRVSTART will wait seconds seconds.
'''Note 1:''' auto_restart will restart the service program if it exits for any reason. If restart_interval is defined, then before restarting, SRVSTART will wait the specified seconds.




'''Note 2:''' auto_restart does not; restart the service program if it is stopped by request (eg NET STOP or Control Panel|Services).
'''Note 2:''' auto_restart does not restart the service program if it is stopped by request (eg NET STOP or Control Panel|Services).




'''Note 3:''' auto_restart does not restart the service program if it thinks that Windows NT is shutting down. If you are irritated by services restarting during Windows NT shutdown, then increase the value of restart_interval to, say, a minute.
'''Note 3:''' auto_restart does not restart the service program if it thinks that Windows NT is shutting down. If you are irritated by services restarting during Windows NT shutdown, then increase the value of restart_interval to, say, a minute.


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==Conclusion==
==Conclusion==


The above has shown how to run a simple VBScipt as a service.
The above has shown how to run a simple VBScipt as a service.
When Uniform Server is installed as a permanent installation concepts outlined above can be used for kicking portable cron into life.
When The Uniform Server is installed as a permanent installation, the concepts outlined above can be used for kicking portable cron into life.
Portable cron is intended to be run from a memory stick and still requires manually starting.
Portable cron is intended to be run from a memory stick and still requires manually starting.


==Where to next==
==Where to next==


Related to the above service is Uniform Server Cron both portable cron and running as a service have been implemented for details see [[Coral: cron intro|Cron]].  
Related to the above service is The Uniform Server Cron. Both portable cron and running as a service have been implemented. For the details, see [[Coral: cron intro|Cron]].  
 
 


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[[Category: Uniform Server 8-Coral]]
[[Category: Uniform Server 8-Coral]]