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Nginx Essentials by Valery Kholodkov

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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 ...

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