killall nginx后无法再启动

某次killall nginx后，nginx服务无法再启动。

ps -ef |grep nginx
root     63703  2548  0 14:34 pts/0    00:00:00 grep --color=auto nginx

查看端口，80端口并无其他服务占用：

netstat -lnpt
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name
tcp        0      0 0.0.0.0:3306            0.0.0.0:*               LISTEN      3181/mysqld
tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN      2097/sshd
tcp        0      0 127.0.0.1:25            0.0.0.0:*               LISTEN      2437/master
tcp        0      0 127.0.0.1:9000          0.0.0.0:*               LISTEN      62906/php-fpm: mast
tcp6       0      0 :::22                   :::*                    LISTEN      2097/sshd
tcp6       0      0 ::1:25                  :::*                    LISTEN      2437/master

然后restart后，Nginx又能正常启动。

/etc/init.d/nginx restart
Restarting nginx (via systemctl):                          [  确定  ]

ps -ef |grep nginx
root     63748     1  0 14:36 ?        00:00:00 nginx: master process /usr/local/nginx/sbin/nginx -c /usr/local/nginx/conf/nginx.conf
nobody   63749 63748  0 14:36 ?        00:00:00 nginx: worker process
nobody   63750 63748  0 14:36 ?        00:00:00 nginx: worker process
root     63752  2548  0 14:36 pts/0    00:00:00 grep --color=auto nginx

端口也成功监听：

netstat -lnpt |grep nginx
tcp        0      0 0.0.0.0:80              0.0.0.0:*               LISTEN      63795/nginx: master

总结下来，确认是Nginx非正常停止导致。