A file with .mpkg extension is an archive installer file, mostly found on MacOS Operating Systems. It contains all required installation files of the application without the need to keep associated files separately. A single MPKG file can contain package files (PKG) as one of the installation files in addition to other files. MPKG files can not be opened with any general software and are executed automatically on MacOS using Apple Installer.
MPKG File Format
An MPKG file contains different types of files that are required for the installation of multiple packages it contains. This is can be seen from the image below which is the tree structure of a sample MPKG file. This tree structure is exported using tree command on MacOS terminal.
The description of different elements in the image is as follow.
Packages Directory - stores a list of pkg files, that is, a list of sub-Packages
Resources Directory - stores resources used by pkg, such as localized resources and images , Rtf documents, pdf documents, etc.
Distribution.dist file - An xml document containing information such as sub-packages to be installed and runtime scripts
Sample XML file for an MPKG file can look as follow depending upon the associated sub-packages.