01 Old nginx nginx binary file into a new file (backup). (Using the command)
02 USR2 signal is sent to the master process, can only send a signal via kill USR2 directly to master the process of nginx, nginx No related commands directly operation. (Using the command)
03nginx process to modify their own pid file name suffix .oldbin
04master process that they will use the new file starts a new master process
05 send WINCH signal to the old master process, close the old worker (using the command)
06 rollback, send HUP signal to the old master, the QUIT signal to the new master. (Using the command)
