yum install xxx报错："Couldn't reso

由于用的是笔记本，使用地点不一样所用的也WLAN不一样，有一次我把电脑带到单位，使用了单位的wifi，发现yum install nc报错："Couldn't resolve host 'mirrorlist.centos.org'"
网上有些帖子说这个错误引起主要是因为环境读取不到yum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，再或者可以考虑清楚yum缓存影响（yum clean all）
首先尝试了第一种方法：

[root@hadoop000 ~]# vim /etc/resolv.conf
nameserver 8.8.8.8
nameserver 202.106.0.20

修改之后发现并没有什么用，然后考虑是不是网络问题
登了一下百度=_=，果然上不去外网了
因为换了wlan，所以网络环境变了

1.查看
2.cmd窗口中输入ipconfig -all
查看

3.在linux中，将该wlan的DNS配置到/etc/sysconfig/network-scripts/ifcfg-eth0中去

[root@hadoop000 ~]# vi /etc/sysconfig/network-scripts/ifcfg-eth0
DEVICE=eth0
HWADDR=00:0C:29:7D:5F:19
TYPE=Ethernet
UUID=ed9645ef-9926-472f-a963-97b7f4c9dbe6
ONBOOT=yes
NM_CONTROLLED=no
BOOTPROTO="static"
IPADDR=192.168.137.251
NETMASK=255.255.255.0
GATEWAY=192.168.137.2
DNS1=192.168.31.1
DNS2=221.130.33.52

4.检查一下网络

5.再次yum install安装成功

[root@hadoop000 ~]# yum install nc -y
Loaded plugins: fastestmirror, refresh-packagekit, security
Loading mirror speeds from cached hostfile
 * base: centos.ustc.edu.cn
 * extras: centos.ustc.edu.cn
 * updates: ftp.sjtu.edu.cn
base                                                            | 3.7 kB     00:00     
extras                                                          | 3.4 kB     00:00     
extras/primary_db                                               |  26 kB     00:00     
http://ftp.sjtu.edu.cn/centos/6.10/updates/x86_64/repodata/repomd.xml: [Errno 14] PYCURL ERROR 7 - "Failed to connect to 2001:da8:8000:6023::230: Network is unreachable"
Trying other mirror.
updates                                                         | 3.4 kB     00:00     
updates/primary_db                                              | 1.2 MB     00:02     
Setting up Install Process
Resolving Dependencies
--> Running transaction check
---> Package nc.x86_64 0:1.84-24.el6 will be installed
--> Finished Dependency Resolution

Dependencies Resolved

=======================================================================================
 Package         Arch                Version                   Repository         Size
=======================================================================================
Installing:
 nc              x86_64              1.84-24.el6               base               57 k

Transaction Summary
=======================================================================================
Install       1 Package(s)

Total download size: 57 k
Installed size: 109 k
Downloading Packages:
nc-1.84-24.el6.x86_64.rpm                                       |  57 kB     00:00     
Running rpm_check_debug
Running Transaction Test
Transaction Test Succeeded
Running Transaction
  Installing : nc-1.84-24.el6.x86_64                                               1/1 
  Verifying  : nc-1.84-24.el6.x86_64                                               1/1 

Installed:
  nc.x86_64 0:1.84-24.el6                                                              

Complete!