虚拟机实验环境：
虚拟机：VMware
操作系统: CentOS
[root@localhost~]# uname -a
Linuxlocalhost.localdomain 2.6.32-573.7.1.el6.i686 #1 SMP Tue Sep 22 19:05:58 UTC2015 i686 i686 i386 GNU/Linux
[root@localhost~]# cat /etc/redhat-release
CentOS release 6.7(Final)
[root@localhost~]# yum –y update
#内核、OS版本、所有软件都会升级，会更改相关配置环境，所以运维人员对于生产服务器操作系统的升级要慎重。
[root@localhost~]#uname –a
Linuxlocalhost.localdomain 2.6.32-642.el6.i686 #1 SMP Tue May 10 16:13:51 UTC 2016i686 i686 i386 GNU/Linux
[root@localhost~]# cat /etc/redhat-release
CentOS release 6.8(Final)
本文出自 “Linux~DBA~MBA~EIE” 博客，请务必保留此出处http://sky9896.blog.51cto.com/2330653/1785055
yum -y upgrade与yum -y update的区别
原文：http://sky9896.blog.51cto.com/2330653/1785055