What is the Windows Installer MSI Package
This article provides an overview of Windows Installer technology, explains how MSI installation works and what are advantages of installations in MSI format.
Windows Installer is a Windows technology that is created for software installation management, tracking software components additions and deletions, and ensuring software configuration consistency at any moment of time. This technology consists of two parts - installer service (msiexec.exe) that is part of the operation system and Microsoft Software Installation (MSI) packages. Installer service manages installation, modification and uninstallation of MSI packages on a computer.
MSI Package Installation - How Does It Work
MSI installation process is handled by Msiexec.exe program. It is a part of Windows Installer that is pre-installed on modern versions of Windows. When MSI installation is initiated, Msiexec.exe reads MSI package content and apply optional MSI transformations and command-line options to define installation parameters. Then the installer performs installation tasks including files copying, applying registry changes, shortcuts creation and so on. Installer may also show installation dialogs and allow to select installation options. Once installation is completed application entry appears in the Add/Remove Programs list. This entry can be used to modify installation or uninstall application. MSI uninstallation actions are also performed by Msiexec.exe program.
Windows Installer Functionality
Windows Installer was designed by Microsoft to improve software management and simplify installation process. Some of most important features of Windows Installer are listed below.
- Support of the system rollback. If MSI installation doesn't succeed Windows Installer restores the system to its initial state. During the installation all system changes are tracked, so it's easy to revert them back if required.
- Program conflicts preventing. Windows Installer enforces installation rules to prevent conflicts when two or more applications install the same shared library (DLL) files. Installer allows to prevent conflicts when such files are created and removed in scope of applications installation and uninstallation.
- Corrupted installations repair. Installation can be repaired quickly by copying missing or corrupted files only. Other resources are skipped by Windows Installer during repairing process.
- Reliable applications uninstallation. During uninstallation Windows Installer removes all files, folders, registry entries being created during installation to remove the application completely. It removes all resources except shared libraries that are still in use by other applications.
- Support of unattended installation. MSI can be deployed in a silent mode with no end-user interaction.
Windows Installer Advantages
Installations in MSI format are standard. It means that you can install, uninstall and manage them on a standard way. Also MSI packages by default support silent installation and can be deployed in automatic mode with no interaction with the user. All these features are important especially for automatic remote software deployment. Group Policy of the Active Directory supports installation of MSI packages, so you can deploy them automatically to hosts across the local network.