Linux troubleshooting

netstat -anop
pstree
ps -ef |grep

systemctl start httpd.service

restart a process: dhcpd
no need: service dhcpd restart
if it show: redirecting to /bin/systemctl restart dhcpd.service 表示这个系统dhcpd服务是没有被特别的运行
有时可能会出现：
[root@localhost ~]# service dhcpd status
Redirecting to /bin/systemctl status dhcpd.service
dhcpd.service - DHCPv4 Server Daemon
Loaded: loaded (/lib/systemd/system/dhcpd.service; enabled)
Active: failed since Wed, 09 Apr 2014 21:37:17 +0800; 1min 17s ago
Process: 2367 ExecStart=/usr/sbin/dhcpd -d -user dhcpd -group dhcpd --no-pid $DHCPDARGS (code=exited, status=1/FAILURE)
CGroup: name=systemd:/system/dhcpd.service
[root@localhost ~]#
的错误，这个是很正常的。表示是说这个dhcpd服务没有以独立的服务运行，是以守护进程的方式出现的。
如果是要结束进程的话
kill -s 9 pgrep dhcpd
重启进程：
dhcpd