问题：Centos 7.3环境，把命令放到 /etc/rc.local后，发现并没有在服务器重启后自动执行。
/etc/rc.local 7.x 后有变化
[root@localhost ~]#
[root@localhost ~]# cat /etc/redhat-release
Red Hat Enterprise Linux Server release 6.7 (Santiago)
[root@localhost ~]#
[root@localhost ~]# cat /etc/rc.local
#!/bin/sh
#
# This script will be executed *after* all the other init scripts.
# You can put your own initialization stuff in here if you don't
# want to do the full Sys V style init stuff.
touch /var/lock/subsys/local
[root@huayd1 huayd]# cat /etc/redhat-release
CentOS Linux release 7.2.1511 (Core)
[root@huayd1 huayd]# cat /etc/rc.local
#!/bin/bash
# THIS FILE IS ADDED FOR COMPATIBILITY PURPOSES
#
# It is highly advisable to create own systemd services or udev rules
# to run scripts during boot instead of using this file.
#
# In contrast to previous versions due to parallel execution during boot
# this script will NOT be run after all other services.
#
# Please note that you must run 'chmod +x /etc/rc.d/rc.local' to ensure
# that this script will be executed during boot.
touch /var/lock/subsys/local
注意到 7.x的环境，多了这么一句描述：
Please note that you must run 'chmod +x /etc/rc.d/rc.local' to ensure
除此之外，还有一个区别，6.x的版本中，明确说明，这个脚本是在其他所有的启动脚本之后执行：
This script will be executed after all the other init scripts.
但7.x的描述有了变化，不在保证 /etc/rc.local一定是在最后执行。
this script will NOT be run after all other services.
实际上，从 7.x 版本开始，引入了 systemd 来管理服务，/etc/rc.local 是为向前兼容而保留。
--End
Mason
