Staging Part 1 – Sharing is Caring

A key phase in installing a package is staging the package:

var packageUri = new Uri("C:\\Packages\\ContosoParts-v1.2.3.4-x64.msix");
var options = new StagePackageOptions();
var packageManager = new PackageManager();
var result = await packageManager.StagePackageByUriAsync(packageUri, options);

When a package is staged for the first time, deployment performs several actions, including:

• Creating a new package directory (commonly referred to as the pkgdir), for example C:\Program Files\WindowsApps\Contoso.Parts_1.2.3.4_x64__1234567890abc
• Extracting the contents of the .msix into the pkgdir
• Applying a tightly restricted access control list (ACL) to the pkgdir
• Creating related directories used for system bookkeeping associated with the package
• Applying similarly restrictive ACLs to these bookkeeping directories

Deployment secures these directories with strict permissions, typically granting users Read and potentially Execute access – but notably not Write access.

This ensures one user cannot modify the contents of a package in a manner that would compromise their own environment – or anyone else’s.

Because MSIX guarantees the immutability of the pkgdir after staging, it can be safely shared across all users on the system – regardless of who installed the package or how many users make use of it.

This immutability also allows MSIX to efficiently minimize on-disk storage for identical content shared across packages.

But more on that in Part 2…