Android升级OTA

• 校验升级包
  调用RecoverySystem类提供的verifyPackage方法进行签名验证

    public static void installPackage(Context context, File packageFile)
        throws IOException {
        String filename = packageFile.getCanonicalPath();
        Log.w(TAG, "!!! REBOOTING TO INSTALL " + filename + " !!!");

        final String filenameArg = "--update_package=" + filename;
        final String localeArg = "--locale=" + Locale.getDefault().toString();
        bootCommand(context, filenameArg, localeArg);
    }

• installPackage开始升级

    public static void installPackage(Context context, File packageFile)
        throws IOException {
        String filename = packageFile.getCanonicalPath();
        Log.w(TAG, "!!! REBOOTING TO INSTALL " + filename + " !!!");

        final String filenameArg = "--update_package=" + filename;
        final String localeArg = "--locale=" + Locale.getDefault().toString();
        bootCommand(context, filenameArg, localeArg);
    }

    private static void bootCommand(Context context, String... args) throws IOException {
        RECOVERY_DIR.mkdirs();  // In case we need it
        COMMAND_FILE.delete();  // In case it's not writable
        LOG_FILE.delete();

        FileWriter command = new FileWriter(COMMAND_FILE);
        try {
            for (String arg : args) {
                if (!TextUtils.isEmpty(arg)) {
                    command.write(arg);
                    command.write("\n");
                }
            }
        } finally {
            command.close();
        }

        // Having written the command file, go ahead and reboot
        PowerManager pm = (PowerManager) context.getSystemService(Context.POWER_SERVICE);
        pm.reboot(PowerManager.REBOOT_RECOVERY);

        throw new IOException("Reboot failed (no permissions?)");
    }

参考：
OTA升级
OTA升级包制作过程
Recovery升级过程