Understanding the Core Principles of APK Installation on Android

The article analyzes the core principles of APK installation on Android, describing four typical scenarios and two main installation pathways: system boot installation and PMS‑driven installation, aiming to clarify the essential steps and underlying logic.

Core installation steps include: (1) parsing AndroidManifest.xml to extract application, component and permission information (e.g., PackageParser.parseBaseApkCommon()); (2) assigning a UID to the app and recording its package information in the PackageManagerService (e.g., PMS.scanPackageDirtyLI(), Setting.addUserIdLPw()); (3) updating the app’s permission state according to the declared uses‑permission entries (e.g., PMS.grantPermissionsLPw()).

System‑boot installation starts with PackageManagerService initialization during the boot process, scanning directories such as /data/app, /system/app, /vendor/app, restoring previous UID assignments from package.xml, and sequentially installing each APK while finally refreshing all permissions.

PMS‑driven installation (used by third‑party apps, ADB, and Market) begins when the PackageInstaller sends an INIT_COPY signal to DefaultContainerService. A Binder/AIDL connection ( IMediaContainerService) is established, and a HandlerParams queue processes installation requests. The startCopy() method copies the APK to the appropriate location, after which handleReturnCode() triggers the core install logic (e.g., installPackageTracedLI()).

Code examples illustrate key points:

public final static class Activity extends Component<ActivityIntentInfo> implements Parcelable

adb shell ps | grep packageName

adb install packagePath

In summary, APK installation consists of parsing the manifest, assigning a UID, and updating permissions; these steps are executed either during system boot or via PMS‑driven mechanisms for user‑initiated installations.