[root@Fort ~]# yum clean all 
已加载插件：fastestmirror
正在清理软件源： mirrors.163.com
Cleaning up everything
Maybe you want: rm -rf /var/cache/yum, to also free up space taken by orphaned data from disabled or removed repos
Cleaning up list of fastest mirrors
[root@Fort ~]# 
[root@Fort ~]# yum update polkit 
已加载插件：fastestmirror
Determining fastest mirrors
mirrors.163.com                                                                                                                              | 3.6 kB  00:00:00     
(1/2): mirrors.163.com/group_gz                                                                                                              | 153 kB  00:00:00     
(2/2): mirrors.163.com/primary_db                                                                                                            | 6.1 MB  00:00:01     
No packages marked for update
[root@Fort ~]# 
[root@Fort ~]# rpm -qa polkit
polkit-0.112-26.el7.x86_64
[root@Fort ~]# 
[root@Fort ~]# yum makecache
已加载插件：fastestmirror
Loading mirror speeds from cached hostfile
mirrors.163.com                                                                                                                              | 3.6 kB  00:00:00     
(1/2): mirrors.163.com/other_db                                                                                                              | 2.6 MB  00:00:01     
(2/2): mirrors.163.com/filelists_db                                                                                                          | 7.2 MB  00:00:05     
元数据缓存已建立
[root@Fort ~]# 
[root@Fort ~]# 
[root@Fort ~]# 
[root@Fort ~]# rpm -qa polkit
polkit-0.112-26.el7.x86_64
[root@Fort ~]#