这个错误引起主要是因为环境读取不到yun引起的可以考虑/etc/sysconfig/network-scripts/ifcfg-eth0 配置出错导致网络不通。或者/etc/resolv.conf的DNS配置出错。或者可以考虑清楚yum缓存影响（yum clean all）

vi /etc/resolv.conf

nameserver 202.106.0.20（今天又出现此错误，这个nameserver加进去就好了。记得配置静态ip的话DNS也需要加入 然后update yum试试成功就OK了）

 

（下面是网上找到比较有用资料）

今天在linux环境通过yum安装软件报了以下错误：

[root@multi-mysql yum.repos.d]# yum install ncurses devel -y
Loaded plugins: fastestmirror, security
Loading mirror speeds from cached hostfile
Could not retrieve mirrorlist http://mirrorlist.centos.org/?release=6&arch=x86_64&repo=os error was
14: PYCURL ERROR 6 - "Couldn't resolve host 'mirrorlist.centos.org'"
Error: Cannot find a valid baseurl for repo: base

从字面意义上看是不能解析mirrorlist.centos.org这个地址，应该是跟dns网络配置有关系，最后解决方法是在DNS域名解析的配置文件增加DNS服务器的IP地址：

[root@multi-mysql ~]# vim /etc/resolv.conf
nameserver 8.8.8.8
nameserver 202.106.0.20

重启网络服务

[root@multi-mysql ~]# /etc/init.d/network restart
Shutting down interface eth0:                              [  OK  ]
Shutting down loopback interface:                          [  OK  ]
Bringing up loopback interface:                            [  OK  ]
Bringing up interface eth0:  Determining if ip address 192.168.1.202 is already in use for device eth0...
                                                           [  OK  ]

重新yum安装，正常

[root@multi-mysql ~]# yum install nmap -y
Loaded plugins: fastestmirror, security
Loading mirror speeds from cached hostfile
 * base: mirrors.yun-idc.com
 * extras: mirrors.yun-idc.com
 * updates: mirrors.yun-idc.com
base                                                                                                         | 3.7 kB     00:00     
base/primary_db                                                                                              | 4.6 MB     00:01     
extras                                                                                                       | 3.4 kB     00:00     
extras/primary_db                                                                                            |  33 kB     00:00     
updates                                                                                                      | 3.4 kB     00:00     
updates/primary_db                                                                                           | 2.6 MB     00:00     
Setting up Install Process
Resolving Dependencies
--> Running transaction check
---> Package nmap.x86_64 2:5.51-4.el6 will be installed
--> Finished Dependency Resolution
......此处省略