Operating System Module Interface Specification

Background¶

• OS module objects are created by State.pm::initialize() when a new state object is created.
• OS module objects are available within state and provisioning modules
• OS module objects are not available within other types of modules for safety.   For example, a monitoring or other utility module should not be able to call the OS module's shutdown subroutine.

OS Module Subroutines¶

It is highly recommended that all OS modules implement the following subroutines.  There may be many additional subroutines implemented within an OS module.  These will not be called by any of the core VCL modules nor any of the provisioning engine modules. #pre_capture #post_load #sanitize #reboot #shutdown #get_current_image_name #reserve #grant_access

  

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pre_capture¶

• Description Configures the OS so that it can be captured by a provisioning module. Configures the OS so that it will successfully boot after the captured image is reloaded on another resource. Adds and configures drivers so that the image will load on other resources. Removes files which should not be saved in the image. Examples of tasks performed by the pre_capture subroutine: Log off users which were created for the imaging reservation and delete the accounts Set root and administrator passwords to standard, known values  Disable and delete page or swap files Delete temp files Copy scripts and utilities to the computer which are required after the computer boots up but before it has network connectivity Copy drivers to the computer * Run a generalization or sealing utility such as Sysprep.exe
• Expected Beginning State Resource is up and accessible Administrator has configured the resource ** Administrator may or may not have logged out
• Expected Ending State (Default) Resource is shut down and turned off Image captured of resource can be loaded and booted on other hardware ** Loaded image will successfully boot up, establish network connectivity, and be accessible by the OS module's post_load() subroutine
• Called By ** Provisioning module's capture() subroutine
• Arguments & Calling Environment Must only be called as an object method of an OS object ($os->pre_capture())  Optional Argument: Name: end_state Type: hash reference Description: Instructs pre_capture() to leave the resource in a particular state after the subroutine's tasks are complet instead of shutting down the resource. Possible Values: on - Leave the resource on.  Do not shut it down or reboot it. * off (Default) - Shut the resource down.* reboot - Initiate a reboot and return.
• Return Values 1 All pre_capture tasks completed successfully. Resource was either shut down or left in the state specified by the end_state argument. Provisioning module can proceed to capture the image. * 0* Resource OS could not be completely prepared to be captured.* Provisioning module should not proceed to capture the image.

post_load¶

• Description Performs tasks to configure the OS after an image was loaded. Does not configure the resource for a particular reservation. Examples of tasks performed by the post_load subroutine: Make sure OS licensing has been activated Configure services Rename the computer or resource Randomize passwords * Configure the firewall
• Expected Beginning State Resource has been powered on  Resource may or may not be accessible ** It's expected that the resource will become accessible automatically after it boots and performs any initialization tasks which were preconfigured by the pre_capture subroutine.
• Expected Ending State ** Resource has been loaded with an image and the OS was configured so that it is ready to be reserved.
• Called By ** Provisioning module's load() subroutine
• Arguments & Calling Environment Must only be called as an object method of an OS object ($os->post_load())  No arguments
• Return Values 1 All OS post-load tasks were completed successfully * 0* All OS post-load tasks could not be completed but the resource became accessible Undefined *** Resource never became accessible

sanitize¶

• Description Reverts the changes made when preparing a resource for a particular reservation. A resource needs to be sanitized if it was successfully reserved for a reservation but not used. The goal of the sanitize subroutine should be to clean up and reconfigure a resource so that it can be provisioned for another reservation without having to be reloaded. An attempt is made to sanitize the resource by reclaim.pm if it determines that the resource was never used for a reservation.  This will occur if a reservation is made, enters the reserved state, but never enters the inuse state. ** Examples of tasks performed by the sanitize subroutine: Delete user accounts which were created for a reservation Revoke access to the resource which was granted for a reservation
• Expected Beginning State
• Expected Ending State 
• Called By reclaim.pm::process() May be called by the same OS module's pre_capture() subroutine to sanitize the resource after it was reserved and used by the image creator.
• Arguments & Calling Environment Must only be called as an object method of an OS object ($os->sanitize()) No arguments will be passed to sanitize()
• Return Values 1 Sanitization was completely successful Resource is ready to be provisioned and reserved for another reservation Resource does not need to be reloaded * 0* Sanitization could not be completed* Resource needs to be reloaded

reboot¶

• Description Performs a complete graceful reboot of the OS. May forcibly log off users if necessary. Waits for the reboot to complete. Returns after the reboot is complete.
• Expected Beginning State Computer is up and accessible. Users may be logged on to the computer.
• Expected Ending State Computer has been rebooted. Computer is accessible.
• Called By ** May be called by any module which has access to the OS object
• Arguments & Calling Environment Must only be called as an object method of an OS object ($os->reboot()) Argument: Name: timeout Description: * Instructs reboot() to wait a maximum number of minutes for the reboot to complete If timeout has been reached and computer has not finished rebooting, 0 should be returned Required: No Default Value: 5 minutes Data Type: integer Possible Values: *** Any positive integer
• Return Values 1 Reboot completed successfully Computer is accessible 0 Reboot was initiated but computer never came back online Timeout was reached Undefined * Reboot could not be initiated

shutdown¶

• Description Performs a graceful shutdown of the OS. May forcibly log off users if necessary. Waits for the shutdown to complete. Returns after the shutdown is complete and the computer is off.
• Expected Beginning State Computer is up and accessible. Users may be logged on to the computer.
• Expected Ending State ** Computer is off.
• Called By ** May be called by any module which has access to the OS object
• Arguments & Calling Environment Must only be called as an object method of an OS object ($os->reboot()) Argument: Name: timeout Description: * Instructs shutdown() to wait a maximum number of minutes for the shutdown to complete If timeout has been reached and computer has not finished shutting down, 0 should be returned Required: No Default Value: 5 minutes Data Type: integer Possible Values: *** Any positive integer
• Return Values 1 Shudown completed successfully * 0 Shutdown was initiated but computer never shut down Timeout was reached * Undefined Shutdown could not be initiated

get_current_image_name¶

• Description Returns the name of the current image that is loaded on the resource(currentimage.txt file). The name corresponds to the image.name column in the database. Returning a name implies that the resource is accessible. The OS.pm will probably handle this subroutine.
• Expected Beginning State ** Resource is accessible.
• Expected Ending State ** The resource state should be identical to before get_current_image_name was called.
• Called By Provisioning module's node_status() subroutine. Used to determine if the OS and provisioning engine agree on the current image loaded on a resource. ** Can be used to determine if a resource is accessible.  A valid string will be returned if the resource is accessible.
• Arguments & Calling Environment Must only be called as an object method of an OS object ($os->get_current_image_name()) No arguments
• Return Values String String contains a VCL image name * 0* Computer is accessible but failed to determine the current loaded image Undefined *** Computer is not accessible

reserve {anchor:reserve}¶

• Description reserve() gets called by new.pm after a machine has been reloaded if the state is "new" (new.pm also handles the "reload" state and others) It should perform the steps necessary to take a reloaded machine and prepare it for a particular reservation Anything reservation-specific that doesn't require knowing the user's IP should be done in reserve() After reserve() has run, the state can be changed to reserved and the "Connect" button can be presented to the user reserve() would normally add the reservation user and any users set in imagemeta usergroup to the computer, set their passwords, and add them to the appropriate groups reserve() does not configure the firewall or do anything networking related because at the time it's called, the state has not been changed to reserved and the user has not been shown the "Connect" button.  Hence, the user's IP is not known. ** reserve() is called by new.pm before the "Connect" button is shown to the user because adding several user accounts may take a long time.  If adding users was done after the state was changed to reserved, a user could attempt to connect before all of the users accounts were added.
• Expected Beginning State Request state is pending/new  Computer has been reloaded
• Expected Ending State Computer has been configured for a particular reservation User accounts have been added and configured ** Request state can be changed to reserved and the "Connect" button can be presented to the user
• Called By ** new.pm
• Arguments & Calling Environment Must only be called as an object method of an OS object ($os->reserve()) No arguments
• Return Values * True (1)  Computer has successfully been configured for a particular reservation * False (0 or undefined)  Computer could not be configured for a particular reservation

grant_access {anchor:grant_access}¶

• Description grant_access() gets called by reserved.pm after the user has clicked the "Connect" button The user's IP address is known when grant_access() is called grant_access() should perform all the steps necessary to open up the machine so the user(s) added by reserve() can connect grant_access() may enables RDP or public SSH traffic depending on the OS
• Expected Beginning State User has just clicked the "Connect" button  Request state is pending/reserved
• Expected Ending State ** Computer has been configured to allow the user to connect
• Called By ** reserved.pm
• Arguments & Calling Environment Must only be called as an object method of an OS object ($os->get_current_image_name()) No arguments
• Return Values * True (1)  Computer was successfully configured to allow access for the reservation users * False (0 or undefined) Computer could not be configured to allow access for the reservation users