mg4/docs/MG4_PLATFORM_INSTALL.md

Installing a Platform-Signed APK on the MG4 Head Unit

This documents the reliable way to install a (platform-signed) APK onto the MG4 SWI69 head unit (Android 9 / SAIC MT2712) over ADB.

The head unit rejects the standard adb install / pm install flow with:

java.io.IOException: Not allowed to install non-system apps on internal storage
	at com.android.internal.content.PackageHelper.resolveInstallVolume(...)

This is not a signature problem — the same platform.pk8 / platform.x509.pem that signs the already-installed com.mg4.* apps signs our APK too (verified by matching SHA-256 cert digests). The PackageManager simply will not let the shell UID (2000) stage a non-system package onto internal storage through its default install path, and --install-location, --force-uuid internal, -l (forward lock) and session-based install-create/install-write/install-commit all hit the same wall or fail to open the file (SELinux denies system_server read access to shell-owned files in some flag combinations).

Prerequisites

• The MG4 head unit connected over ADB (adb devices lists it).
• A built APK. For a platform-signed build see MG4_PLATFORM_BUILD.md (DiPlay) — the same zipalign + apksigner sign --key tools/platform.pk8 --cert tools/platform.x509.pem step applies here.
• The platform keys in tools/ (platform.pk8, platform.x509.pem).

The Install Command

The only flag combination that works on this unit is:

adb push <your-app>.apk /data/local/tmp/update.apk
adb shell "pm install -r -f -d -t /data/local/tmp/update.apk"

Flags:

• -r — replace the existing package if one is installed.
• -f — force install on internal flash (/data/app/).
• -d — allow a version-code downgrade (debuggable packages only). The unstable channel bumps versionCode per CI build, so a locally built APK is almost always lower than whatever the OTA last pushed; without -d the install silently fails on a version mismatch.
• -t — allow test packages. Unstable/debug builds are marked debuggable, which the PackageManager treats as a test package.

The file must be pushed as (or renamed to) something under /data/local/tmp/. Other locations (/sdcard/, a custom cache dir) fail with Can't open file because system_server has no SELinux read access to those contexts. A failed pm install attempt can delete the staged file, so if a later install says No such file or directory, re-push.

Verifying the Install

adb shell pm path com.stinnesbeck.nilsmg4.unstable
# -> package:/data/app/com.stinnesbeck.nilsmg4.unstable-.../base.apk

To confirm the platform signature matches the system:

BUILD_TOOLS="$ANDROID_HOME/build-tools/36.0.0"
adb pull "$(adb shell pm path com.stinnesbeck.nilsmg4.unstable | sed 's/package://')" /tmp/installed.apk
"$BUILD_TOOLS/apksigner" verify --print-certs /tmp/installed.apk
# SHA-256 cert digest should match tools/platform.x509.pem

Uninstalling

adb uninstall com.stinnesbeck.nilsmg4.unstable

Add -k to keep data/cache around (useful when re-installing to test without wiping the local consumption store).

End-to-End: Build → Sign → Install

From the repository root:

# 1. Build
./gradlew :app:assembleUnstableDebug

# 2. Align + platform-sign
SDK="$HOME/Library/Android/sdk"
BT="$SDK/build-tools/36.0.0"
IN=app/build/outputs/apk/unstable/debug/app-unstable-debug.apk
ALIGNED=app/build/outputs/apk/unstable/debug/app-unstable-debug-aligned.apk
OUT=NilsMG4-unstable-platform.apk
"$BT/zipalign" -f 4 "$IN" "$ALIGNED"
"$BT/apksigner" sign --key tools/platform.pk8 --cert tools/platform.x509.pem --out "$OUT" "$ALIGNED"
"$BT/apksigner" verify --verbose "$OUT"

# 3. Install on the head unit
adb push "$OUT" /data/local/tmp/update.apk
adb shell "pm install -r -f -d -t /data/local/tmp/update.apk"