In this multi-part series, we take a look at under covers of files that make up an App-V package. Some of these files are in binary format, which makes them interesting more or less to those of us who develop software, while those files that are human-readable (XML formatted) textual data can easily be examined and edited by App-V administrators and packagers using normal text editors and tools.

 

Overview of package files

We begin our journey to App-V files by taking an overview on what files (by extensions) you generally can expect to see when looking at the directory holding a complete App-V package:

.SPRJ file

This file, of which there is only one per each package, is Softricity Project File, binding logically all other package’s files together. This file is used by the Sequencer and optionally Management Console which is associated with Management Server –based infrastructure.

.OSD files

Per each package, there could be a multitude of these files, which derives its name from ages old (and mostly forgotten) RFC note called The Open Software Description Format (http://www.w3.org/TR/NOTE-OSD.html), originating from Microsoft and company no longer with us, called Marimba. This file used and required by the Sequencer and App-V Client, each OSD file representing one single startable application from the package. Or as another way to look at it, each one representing one particular shortcut you intend to publish to client machines.

.SFT file

This file which got its name from Softricity, the company who originally created App-V, nee SoftGrid, is the second absolutely required file by the App-V Client. It contains all the actual content (applications and related files plus virtual environment) of the App-V package, packaged in binary format somewhat like in ZIP archive.

.ICO files

In one package, there could be number of standard Windows icon files, which map either to application shortcuts (i.e. OSD files) or to file types associated with individual applications found inside the package. Since App-V packages do not carry executable (EXE) files for applications outside the virtual environment, Windows needs to have icon files separately so that users can see familiar program and document icons when virtual applications has been deployed to their machines. For this reason, Sequencer extracts these icons as “naked” ICO files to the package directory.

.XML file

Each package has one package publishing -related file, called Manifest file. This file contains aggregated information from SPRJ file and OSD files, and it is used (quite rarely directly) by App-V Client but more prominently so by Microsoft System Center Configuration Manager (SCCM) to make the whole App-V package and all individual applications from it available to the client, when no App-V Management Server is available as source for publishing information.

.MSI file

As an optional and additional file, standard Windows Installer database, MSI, is created by the Sequencer, one per each package. This MSI can be used to deliver the package to App-V Clients as alternative way to using App-V Management Server publishing or SCCM delivery.

 

In addition to these physical files that you can observe directly in the package directory, each SFT file holds – among other application related files – one App-V package specific file which is also referenced from each and every OSD file in the package:

.CP file

This special file, having extension officially coming from “Computer Protection” (thanks for Tim for revealing that bit of info ;-)), is the virtual environment’s configuration file for the package. It contains not only the virtual registry in it, but also something called Virtual Filesystem (VFS), and it is used by the App-V Client while establishing (or “uploading”) Virtual Environment when virtual application is launched.

 

In the upcoming articles of this series, we will take a closer look at the contents of following file types described above: SFT, CP, OSD, SPRJ and XML.

Stay tuned!