If Google had known the mess Android updates would become, it probably would have taken a different approach to distribution. Alas, Google gave device makers control over almost every aspect of the OS early on and has been trying to make up for that decision ever since. Its latest effort to make Android easier to update is known as Project Mainline. This Android Q component allows Google to patch certain core system components without an OTA update.
In Android Pie and earlier, changes to core system components require an update. Some phones can install these updates in the background, mandating a restart to initialize the new code. Others like Samsung only install the update during restart, which means several minutes of downtime. Project Mainline can update important parts of the OS silently without a restart.
According to Google, Mainline can update 12 core components via the Play Store. For the record, here are all the supported OS modules:
- Security: Media Codecs, Media Framework Components, DNS Resolver, Conscrypt
- Privacy: Documents UI, Permission Controller, ExtServices
- Consistency: Timezone data, ANGLE (developers opt-in), Module Metadata, Networking components, Captive Portal Login, Network Permission Configuration
These aren’t parts of Android you think about a lot, but you interact with them constantly. To update these components live, Google developed a new file container called APEX (Android Pony EXpress). APEX is similar to the APK container for app distribution. Android Q processes APEX files in the same package manager that installs your apps, but instead of an app, APEX files contain new system components.
This is part of Google’s ongoing effort to accelerate Android updates. Years back, it started pulling pieces out of the core OS and packaging them up inside Play Services, which it can update silently in the background. In Oreo, Google added support for Project Treble, making the platform more modular, encouraging faster updates and longer support windows.
Because of limitations in older Linux kernels, Project Mainline won’t work on most devices that get updates to Android Q. Phones that ship with Q should have support baked in. Google says it will roll Mainline updates out to all phones in a matter of weeks via the Play Store. We can expect that to start happening with the 2019 Pixel phones when they launch late this year.
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