'Start the specified subsystem.
Args:
subsystem [string]: The name of the subsystem.
environ [dict]: If set, use these environment variables instead.
Returns:
The pid of the subsystem once running.'

def start_subsystem(self, subsystem, environ=None):

    print 'Starting    {subsystem}'.format(subsystem=subsystem)
    command = os.path.join(self.__installation.SUBSYSTEM_ROOT_DIR, subsystem, 'bin', subsystem)
    base_log_path = os.path.join(self.__installation.LOG_DIR, subsystem)
    return self.run_daemon('/bin/bash', ['/bin/bash', '-c', '("{command}"    >    "{log}.log")    2>&1    |    tee    -a    "{log}.log"    >&    "{log}.err"'.format(command=command, log=base_log_path)], environ=environ)
