[root@localhost pid]# /usr/sbin/postfix start
postfix/postfix-script: warning: not owned by postfix: /var/lib/postfix/.
postfix/postfix-script: warning: not owned by postfix: /var/lib/postfix/./master.lock
postfix/postfix-script: starting the Postfix mail system

[root@localhost pid]# rm -rf /var/lib/postfix/./master.lock 删除.lock文件

再次启动：
[root@localhost pid]# /usr/sbin/postfix start
postfix/postfix-script: warning: not owned by postfix: /var/lib/postfix/.
postfix/postfix-script: starting the Postfix mail system

[root@localhost pid]# chown postfix.postfix /var/lib/postfix/
[root@localhost pid]# chmod og-w /var/lib/postfix/
[root@localhost pid]# /usr/sbin/postfix start
postfix/postfix-script: starting the Postfix mail system
[root@localhost pid]# service postfix stop
Shutting down postfix:                                     [  OK  ]
[root@localhost pid]# service postfix restart
Shutting down postfix:                                     [FAILED]
Starting postfix:                                          [  OK  ]
[root@localhost pid]# /usr/sbin/postfix start
postfix/postfix-script: fatal: the Postfix mail system is already running
启动成功

postfix启动失败