SMS: SMSINST: Automatic Rollback With the SMS Installer (200374)


The information in this article applies to:

  • Microsoft Systems Management Server Installer 1.0
This article was previously published under Q200374

SUMMARY

The SMS Installer contains the ability to update an existing application installation, such as Modify the installation (make INI and registry changes) and to install updated executables and data files. With this ability comes the facility to backup the changes made during an update to an existing installation. The SMS Installer can provide the framework to automatically backup replaced files, registry and INI file changes during an installation. It is then possible at a later point to roll back the installation to the previously installed state.

MORE INFORMATION

To enable rollback support, the SMS Installer must have the following options enabled:

  • Uninstall Support - Enabled from the Script Editor through the Run-time Support, Run-time Options, and Uninstall Support.

    This option adds an Include Script item to the script that copies the uninstall support executable to the installation directory (Uninstal.exe or Uninst32.exe) and adds uninstall support to the registry for Windows 9x and Windows NT client.

  • Backup Replaced Files - Enabled from the Script Editor through Installation Interface, Wizard Dialogs, and Backup Replaced Files.

    This option adds a new custom dialog to the wizard block within the script called Select Backup Directory. During an installation, the user is prompted for a directory in which to place previous versions of files that the current installation will modify. During a rollback, the previous versions of the files held in the backup directory will replace the current versions of the files for the application.
When Rollback support is enabled, the BACKUP script variable stores the location of the backup directory used to store original files changed by the installation. The default script sets the BACKUP variable to %MAINDIR%\BACKUP (the directory BACKUP is created underneath the main installation directory). If the installation is performed in interactive mode, the user is prompted to select a backup directory in which to place original files (only files that will be replaced/modified by files contained within the SMS Installer package are placed in the backup directory). The DOBACKUP variable is set to A, and the BACKUPDIR variable is set to the contents of the BACKUP variable (%MAINDIR%\BACKUP is the default). The SMS Installer uses the BACKUPDIR variable as the path to move files about to be replaced.

Support for Multiple Builds and Incremental Rollback:

If the installed package is updated more than once with rollback support enabled, the install.log is appended with the set of changes by each installation. When files are replaced by updated versions, the copy to be replaced is moved to the BACKUP directory. If the file has been updated in a previous installation, a file with that name will already exist in the BACKUP directory, and the file being moved is automatically given the extension 001. As more updates occur, replaced files are moved to the BACKUP directory and the extension incremented (file.001, file.002, etc.).

It is therefore possible to roll back an installation to the previous build and then to a build prior to that, if it exists. If a rollback is performed on an installation that contains no backups, the rollback is treated as a deinstallation (the application is removed).

If the SMS Installer package is executed with the /S (Silent) command line option, then custom dialogs are not displayed. The default contents of the BACKUP variable (%MAINDIR%\BACKUP) are used as the backup path for rollback support. Original files that are about to be replaced are copied to the backup directory automatically.

Performing a rollback:

If rollback support is available when the user selects to uninstall an application (either via Control Panel,Add/Remove Programs or through Uninstal.exe/Uninst32.exe), the SMS Installer uninstall program will ask the user if the installation should be rolled back. Upon selecting Yes (perform a rollback), information about files, registry, and INI file changes will be obtained from the install.log and a rollback performed (files from the backup directory will be copied back to their original location to replace the prior versions).

Performing rollbacks automatically:

The uninstall programs Uninstal.exe/Uninst32.exe support a number of command line parameters that affect their functionality. When an uninstall is performed without any command line parameters, multiple dialogs can be presented to the user depending upon the installation type performed initially. The first dialog produced is the Uninstall Method preferred by the user.

This can be Automatic or Custom:
  • Automatic affects all files included in the installation.

  • Custom requests the user to select files files for removal.
A second dialog "Perform Rollback" is presented if the installation supports rollback (a prior installation had rollback support enabled). This gives the choice of Yes or No:
  • Yes - Rolls back the installation to the previous build if it exists. Changes to files and the registry are rolled back to the previous installation.

  • No - The installation is removed in its entirety.
Command line options for Uninstal.exe/Uninst32.exe are as follows :
/A Perform and automatic uninstall
/S Perform a silent uninstall
/R Perform a rollback

e.g. UNINSTAL.EXE /S /A /R x:\path\install.log

The path to the install.log is optional. This does not need to be supplied if the install.log is in the same directory as the uninstal.exe program.

The above command line performs a silent, automatic rollback of the installation.
Modification Type:MinorLast Reviewed:6/14/2005
Keywords:kbinfo kbRegistry KB200374
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