How does macOS install apps downloaded from Mac App Store?

[brante]

Hi

As far as I know generally when you try to download an app from Mac App Store eventually it will create a folder in /var/folders/XX/[alphanumerics]/C/com.apple.appstoreagent/com.apple.appstore/[UUID] and then 4 files will be downloaded, .pkg .pfpkg receipt & flyingicon. I know it's so complicated to even get to this stage but I am curious what's the next step? How the app is gonna be installed after this stage?

Just went ahead and tried to open that .pkg file but it threw an error [com.apple.installer.pagecontroller error -1] so apparently it's not installable at least for now.

Can you please let me know what is going to happen to these files and why the .pkg file is not ready to use?


Thank you.

 

[chscag]

Every app I've downloaded from the Mac App Store installed itself. There's no need to worry about those other files.

Even complex apps such as Microsoft Office 365 installs itself.

What kind of problems are you having?

 

[brante]

No any kind of problem.

Everything is installing fine and nothing to complain about!

Actually I'm curious to know the technical steps behind the scene on how Mac App Store makes a .app in /Applications/ out of those 4 downloaded files and why that .pkg is not installable?

 

[chown33]

There can be many reasons why a .pkg isn't installable. For example, the download might have malfunctioned in some way, so the .pkg contents is damaged.

I did a web search for "preflight.pfpkg" (including the quotes), and one of the top hits is this:

How to get the best out of the App Store

Understanding the different stages which occur when you update an App Store app is crucial to dealing with problems, and using an optimal workflow.

eclecticlight.co

It describes some problems with updates, and looks at some of the inner workings of App Store downloads, at least as far as they apply to updates.

Here's the follow-up article mentioned, and it's much more detailed about the sequence of events:

Inside the App Store: how it delivers your apps

Detailed step-by-step account of how apps are downloaded and updated from the App Store. Welcome new internal names like Absinthe, Jetpack, and Crossfire, and Apple’s fraud score.

eclecticlight.co

That article mentions log entries, which should be viewable using Console.app, and should be present on a default OS.


There might be other developer tools that let you poke around in the .pkg, and do things like list things, check signatures, etc. It's almost certain that those would be command-line tools, so if you're familiar with Terminal you might start using just the basics like 'ls', 'cat', 'hexdump', etc.

Other tools might be present in an Xcode download, so look there. Beyond that, you'll probably need to look at websites where lots of Mac developers hang out.

 

[brante]

There can be many reasons why a .pkg isn't installable. For example, the download might have malfunctioned in some way, so the .pkg contents is damaged.

I did a web search for "preflight.pfpkg" (including the quotes), and one of the top hits is this:

How to get the best out of the App Store

Understanding the different stages which occur when you update an App Store app is crucial to dealing with problems, and using an optimal workflow.

eclecticlight.co

It describes some problems with updates, and looks at some of the inner workings of App Store downloads, at least as far as they apply to updates.

Here's the follow-up article mentioned, and it's much more detailed about the sequence of events:

Inside the App Store: how it delivers your apps

Detailed step-by-step account of how apps are downloaded and updated from the App Store. Welcome new internal names like Absinthe, Jetpack, and Crossfire, and Apple’s fraud score.

eclecticlight.co

That article mentions log entries, which should be viewable using Console.app, and should be present on a default OS.


There might be other developer tools that let you poke around in the .pkg, and do things like list things, check signatures, etc. It's almost certain that those would be command-line tools, so if you're familiar with Terminal you might start using just the basics like 'ls', 'cat', 'hexdump', etc.

Other tools might be present in an Xcode download, so look there. Beyond that, you'll probably need to look at websites where lots of Mac developers hang out.

tbh I thought it's going to be lots easier to figure it out but apparently it's not the case. So yeah probably I have to go through the articles and ask for some help in dev's community.

Thanks for your answer, really appreciate it.