NginX Log Rotation

It has become a sort-of informal semi-standard among Unix daemons that they flush and/or rotate their log files, when you send them a hangup signal (SIGHUP). Nginx doesn't follow this convention to the letter, but it responds to the USR1 signal the same way, as is documented on the Nginx website under the title Log Rotation.

So, you could try something like

kill -s USR1 `pidof nginx`

logrotating nginx logs:

# nginx SIGUSR1: Re-opens the log files.
/opt/nginx/logs/access.log {
  missingok
  notifempty
  delaycompress
  sharedscripts
  postrotate
    test ! -f /opt/nginx/logs/nginx.pid || kill -USR1 `cat /opt/nginx/logs/nginx.pid`
 endscript 
}

/opt/nginx/logs/error.log {
  missingok
  notifempty
  delaycompress
  sharedscripts
  postrotate  
    test ! -f /opt/nginx/logs/nginx.pid || kill -USR1 `cat /opt/nginx/logs/nginx.pid`
  endscript
}

logrotating rails production log:

/home/app_user/apps/railsapp/log/production.log {
  missingok
  notifempty
  delaycompress
  sharedscripts
  postrotate
    test ! -f /opt/nginx/logs/nginx.pid || kill -USR1 `cat /opt/nginx/logs/nginx.pid`
  endscript
}

If you use logrotate, add the following (with correct location) into nginx's section of logrotate.conf:

postrotate
  kill -s USR1 `cat /location/of/nginx.pid`
endscript

According to logrotate(8) man page