Generating the keys

From the root of your Android tree, run these commands, altering the subject line to reflect your information:

subject='/C=US/ST=California/L=Mountain View/O=Android/OU=Android/CN=Android/emailAddress=android@android.com'
mkdir ~/.android-certs
for x in releasekey platform shared media; do \
    ./development/tools/make_key ~/.android-certs/$x "$subject"; \
done

You should keep these keys safe, and store the passphrase in a secure location.

Generating an install package

Generating and signing target files

After following the build instructions for your device, instead of running brunch <codename>, run the following:

breakfast <codename>
mka target-files-package dist

Sit back and wait for a while - it may take a while depending on your computer’s specs. After it’s finished, you just need to sign all the APKs:

croot
./build/tools/releasetools/sign_target_files_apks -o -d ~/.android-certs \
    out/dist/*-target_files-*.zip \
    signed-target_files.zip

Generating the install package

Now, to generate the installable zip, run:

./build/tools/releasetools/ota_from_target_files -k ~/.android-certs/releasekey \
    --block --backup=true \
    signed-target_files.zip \
    signed-ota_update.zip

Then, install the zip in recovery as you normally would.

Changing keys

Using a migration build

You can set up your own migration builds by running:

repopick -f 156047 162144

Then, follow the instructions to generate an install package.

Going back

After installing the migration build, you can switch back to building normal builds:

cd vendor/cm
git reset --hard github/cm-14.1
croot
cd frameworks/base
git reset --hard github/cm-14.1

Using a script

You can also use a script or small flashable zip designed to be run once, before installing a build with the new keys. The script is available under ./lineage/scripts/key-migration/script.sh

The script can also be made into a zip, by inserting it into a zip similar to this. This zip has the script placed in META-INF/com/google/android/update-binary with some additions to print status messages to the recovery.

Test-keys to official or vice versa

If you are moving from a test-keys build (eg an “unsigned” unofficial build) to an official LineageOS build, you can push the script to your device and run it from Android:

adb root # This requires an userdebug/eng build and ADB root access to be enabled
adb shell stop
adb push ./lineage/scripts/key-migration/migrate.sh /data/local/tmp/migrate.sh
adb shell chmod +x /data/local/tmp/migrate.sh
adb shell sh /data/local/tmp/migrate.sh official
adb reboot recovery
# Now install the official LineageOS install zip

Or run it from recovery:

# Ensure both /data and /system are mounted, then continue
adb push ./lineage/scripts/key-migration/migrate.sh /data/local/tmp/migrate.sh
adb shell chmod +x /data/local/tmp/migrate.sh
adb shell /data/local/tmp/migrate.sh official

If you are migrating from an official build to your own “unsigned” builds, you can run the script in the same way, but instead using the argument “unofficial” instead of “official”.

Test-keys to your own release-keys or vice versa

If you are moving from test-keys to your own signed builds, you can add your own keys to the script. First, export your keys to the required format, by running the script in ./lineage/scripts/key-migration/export-keys.sh.

This will print the keys and certs to the terminal in the format required. Next, edit the script to use your keys. You will need to comment out (by prepending a #), or remove the existing definitions of the “release” keys and certs. Now, copy and paste your output from above into the script where the previous lines were. Make sure to leave the “test” keys and certs definitions untouched.

Your script is ready to go! Push it to the device and run it, in the same way as described above, then install your own signed zip. If you ever need to run this in reverse, simply use the “unofficial” argument instead of “official”, and your keys will be replaced with the official keys.