Nginx Essentials

Control signals and their usage

Nginx, like any other Unix background service, is controlled by signals. Signals are asynchronous events that interrupt normal execution of a process and activate certain functions. The following table lists all signals that Nginx supports and the functions that they trigger:

Signal	Function
TERM, INT	Fast shutdown
QUIT	Graceful shutdown
HUP	Reconfiguration
USR1	Log file reopening
USR2	Nginx binary upgrade
WINCH	Graceful worker shutdown

All signals must be sent to the master process of an instance. The master process of an instance can be located by looking it up in the process list:

# ps -C nginx -f
UID        PID  PPID  C STIME TTY          TIME CMD
root 4754 3201 0 11:10 ? 00:00:00 nginx: master process ...