一、主进程控制信号

TERM, INT fast shutdown
QUIT graceful shutdown
HUP changing configuration, keeping up with a changed time zone (only for FreeBSD and Linux), starting new worker processes with a new configuration, graceful shutdown of old worker processes
USR1 re-opening log files
USR2 upgrading an executable file
WINCH graceful shutdown of worker processes

二、工作进程控制信号

TERM, INT fast shutdown
QUIT graceful shutdown
USR1 re-opening log files
WINCH abnormal termination for debugging (requires debug_points to be enabled)

三、参考文章

http://www.nginx.cn/nginxchscommandline
http://nginx.org/en/docs/control.html