# yum check-update
# yum update [PACKAGE_NAME] ...
//检测系统已安装软件包是否有更新
[root@localhost ~]# yum check-update
Loaded plugins: fastestmirror, security
Loading mirror speeds from cached hostfile
* base: mirrors.163.com
* extras: mirrors.163.com
* updates: mirrors.163.com
initscripts.x86_64 9.03.40-2.el6.CentOS.1 updates
libtiff.x86_64 3.9.4-10.el6_5 updates
phonon-backend-gstreamer.x86_64 1:4.6.2-28.el6_5 updates
postfix.x86_64 2:2.6.6-6.el6_5 updates
psmisc.x86_64 22.6-19.el6_5 updates
upstart.x86_64 0.6.5-13.el6_5.2 updates
//更新软件包"postfix"
[root@localhost ~]# yum update postfix
//更新所有可更新的软件包
[root@localhost ~]# yum update
# yum reinstall PACKAGE_NAME ...