List of Built-In Task OSD Sequence Variables

Built-in Variable Name	Description
_SMSTSAdvertID	Stores the current running task sequence advertisement ID. It uses the same format as a Configuration Manager 2007 software distribution advertisement ID. If the task sequence is running from stand-alone media, this variable is undefined. Example: ABC20001
_SMSTSBootImageID	Stores the Configuration Manager 2007 boot image package ID if a boot image package is associated with the current running task sequence. The variable will not be set if no Configuration Manager 2007 boot image package is associated. Example: ABC00001
_SMSTSClientGUID	Stores the value of Configuration Manager 2007 client GUID. This variable is not set if the task sequence is running from stand-alone media. Example: 0a1a9a4b-fc56-44f6-b7cd-c3f8ee37c04c
_SMSTSCurrentActionName	Specifies the name of the currently running task sequence step. This variable will be set before the task sequence manager runs each individual step. Example: run command line
_SMSTSDownloadOnDemand	Set to true if the current task sequence is running in download-on-demand mode, which means the task sequence manager downloads content locally only when it must access the content.
_SMSTSInWinPE	This variable is set to true when the current task sequence step is running in the Windows PE environment, and it is set to false if not. You can test this task sequence variable to determine the current operating system environment.
_SMSTSLastActionRetCode	Stores the return code returned by the last action that was run. Example: 0
_SMSTSLastActionSucceeded	The variable is set to true if the last action succeeded and to false if the last action failed. If the last action was skipped because the step was disabled or the associated condition evaluated to false, this variable is not reset, which means it still holds the value for the previous action.
_SMSTSLaunchMode	Specifies the task sequence launch method. The task sequence can have the following values: SMS - specifies that the task sequence is started by using the Configuration Manager 2007 client. UFD - specifies that the task sequence is started by using USB media. CD - specifies that the task sequence is started by using CD/DVD sets. PXE - specifies that the task sequence is started from PXE.
_SMSTSLogPath	Stores the full path of the log directory. This can be used to determine where actions should be logged. This value is not set when no hard drive is available.
_SMSTSMachineName	Stores and specifies the computer name. Stores the name of the computer that the task sequence will use to log all status messages. To change the computer name in the new operating system, use the OSDComputerName variable. Example: ABC
_SMSTSMediaType	Specifies the type of media that will be used to initiate the installation. Examples of types of media are Boot Media, Full Media, PXE, and Prestaged Media.
_SMSTSMP	Stores the name or IP address of a Configuration Manager 2007 management point.
_SMSTSMPPort	Stores the management point port number of a Configuration Manager 2007 management point. Example: 80
_SMSTSOrgName	Stores the branding title name, which will be displayed in a task sequence progress user interface dialog box. Example: XYZ Organization
_SMSTSPackageID	Stores the current running task sequence ID. This ID uses the same format as a Configuration Manager 2007 software package ID. Example: HJT00001
_SMSTSPackageName	Stores the current running task sequence name specified by the Configuration Manager 2007 administrator when the task sequence is created. Example: Deploy xpsp2 task sequence
_SMSTSRunFromDP	Set to true if the current task sequence is running in run-from-distribution-point mode, which means the task sequence manager obtains required packages from distribution point shares.
_SMSTSSiteCode	Stores the site code of the Configuration Manager 2007 site. Example: ABC
_SMSTSType	Specifies the type of the current running task sequence. It can have the following values: 1 - indicates a generic task sequence. 2 - indicates an operating system deployment task sequence.
_SMSTSTimezone	The _SMSTSTimezone variable stores the time zone information in the following format (without spaces): Bias, StandardBias, DaylightBias, StandardDate.wYear, wMonth, wDayOfWeek, wDay, wHour, wMinute, wSecond, wMilliseconds, DaylightDate.wYear, wMonth, wDayOfWeek, wDay, wHour, wMinute, wSecond, wMilliseconds, StandardName, DaylightName Example For the Eastern Time U.S. and Canada, the value would be 300,0,-60,0,11,0,1,2,0,0,0,0,3,0,2,2,0,0,0,Eastern Standard Time,Eastern Daylight Time
_SMSTSUseCRL	Specifies whether the task sequence uses the certificate revocation list when it uses a Secure Socket Layer (SSL) certificate to communicate with the management point.
_SMSTSUserStarted	Specifies whether a task sequence is started by a user. This variable will only be set if the task sequence is started from the Configuration Manager 2007 client. For example, if _SMSTSLaunchMode is set to SMS. The variable can have the following values: true - specifies that the task sequence is manually started by a user from the client Run Advertised Programs program. false - specifies that the task sequence is initiated automatically by the Configuration Manager 2007 scheduler.
_SMSTSUseSSL	Specifies whether the task sequence uses SSL to communicate with the Configuration Manager 2007 management point. If your site is running in native mode, the value is set to true.
SMSTSErrorDialogTimeout	When an error occurs in a task sequence, a dialog box is displayed that is dismissed automatically after a default time-out value. Use this variable to specify a time-out value in seconds other than the default of 15 minutes.
SMSTSRebootDelay	Specifies how many seconds to wait before the computer restarts. The task sequence manager will display a notification dialog before reboot if this variable is not set to 0. Examples: 0 30
SMSTSRebootMessage	Specifies the message to display in the shutdown dialog box when a reboot is requested. If this variable is not set, a default message will appear. Example: This computer is being rebooted by the task sequence manager.
SMSTSRebootRequested	Indicates that a reboot is requested after the current task sequence step is completed. If a reboot is required, just set this variable to true, and the task sequence manager will restart the computer after this task sequence step. The task sequence step must set this task sequence variable if it requires a reboot to complete the task sequence step. After the computer is rebooted, the task sequence will continue to run from the next task sequence step.
SMSTSLocalDataDrive	Specifies where temporary files are stored on the destination computer while the task sequence is running.
SMSTSRetryRequested	Requests a retry after the current task sequence step is completed. If this task sequence variable is set, the SMSTSRebootRequested must also be set to true. After the computer is restarted, the task sequence manager will rerun the same task sequence step.

Reference:
Creating Your Own Task Sequence Variables
Operating System Deployment Task Sequence Variables