In NginxController, you'd add something like:

    @SetFromFlag("pcreVersion")
    public static final ConfigKey<String> PCRE_VERSION =
        new BasicConfigKey<String>(String.class, "pcre.version", "Version of PCRE to be installed, if required", "8.32");

And then in NginxSshDriver.install, you'd do:

    pcreVersion = entity.getConfig(PCRE_VERSION)