[root@test]# /etc/init.d/nginx restartnginx: [error] invalid PID number "" in "/usr/local/nginx/logs/nginx.pid"[root@test]# ps aux|grep nginx root      1576  0.0  0.1  47880  4124 ?        Ss   08:53   0:00 nginx: master process /usr/local/nginx/sbin/nginx -c /usr/local/nginx/conf/nginx.confwww       1581  0.0  0.6  68028 24588 ?        S    08:53   0:00 nginx: worker process                                          www       1582  0.0  0.6  67892 24392 ?        S    08:53   0:00 nginx: worker process                                          www       1583  0.0  0.6  67892 24392 ?        S    08:53   0:00 nginx: worker process                                          www       1584  0.0  0.6  68260 25084 ?        S    08:53   0:00 nginx: worker process                                          www       1585  0.0  0.6  67892 24392 ?        S    08:53   0:00 nginx: worker process                                          www       1586  0.0  0.6  68028 24688 ?        S    08:53   0:00 nginx: worker process                                          www       1587  0.0  0.6  68292 24868 ?        S    08:53   0:00 nginx: worker process                                          www       1588  0.0  0.6  68556 25152 ?        S    08:53   0:00 nginx: worker process  [root@test]# cat /usr/local/nginx/logs/nginx.pid[root@test]# echo 1576 > /usr/local/nginx/logs/nginx.pid[root@test]# /etc/init.d/nginx restart