CentOS 7安裝完後無法上網的解決辦法

發現問題：

[root@mydocker network-scripts]# wget http://mirrors.163.com/.help/CentOS7-Base-163.repo
--2016-10-01 09:43:12--  http://mirrors.163.com/.help/CentOS7-Base-163.repo
正在解析主機 mirrors.163.com (mirrors.163.com)... 失敗：未知的名稱或服務。
wget: 無法解析主機地址 “mirrors.163.com”
[root@mydocker network-scripts]# yum update
已載入外掛程式：fastestmirror, langpacks
http://mirrors.163.com/centos/7/os/x86_64/repodata/repomd.xml: [Errno 14] curl#6 - "Could not resolve host: mirrors.163.com; 未知的錯誤"
正在嘗試其它鏡像。




 One of the configured repositories failed (CentOS-7 - Base - 163.com),
 and yum doesn't have enough cached data to continue. At this point the only
 safe thing yum can do is fail. There are a few ways to work "fix" this:


     1. Contact the upstream for the repository and get them to fix the problem.


     2. Reconfigure the baseurl/etc. for the repository, to point to a working
        upstream. This is most often useful if you are using a newer
        distribution release than is supported by the repository (and the
        packages for the previous distribution release still work).


     3. Disable the repository, so yum won't use it by default. Yum will then
        just ignore the repository until you permanently enable it again or use
        --enablerepo for temporary usage:


            yum-config-manager --disable base


     4. Configure the failing repository to be skipped, if it is unavailable.
        Note that yum will try to contact the repo. when it runs most commands,
        so will have to try and fail each time (and thus. yum will be be much
        slower). If it is a very temporary problem though, this is often a nice
        compromise:


            yum-config-manager --save --setopt=base.skip_if_unavailable=true


failure: repodata/repomd.xml from base: [Errno 256] No more mirrors to try.
http://mirrors.163.com/centos/7/os/x86_64/repodata/repomd.xml: [Errno 14] curl#6 - "Could not resolve host: mirrors.163.com; 未知的錯誤"

定位問題：

根據上面的錯誤提示，應該是網域名稱解析不了，那麼我們需要設定CentOS 7的網域名稱解析規則。

解決方案：

在/etc/resolv.conf檔案中添加一行內容為：/etc/resolv.conf ，具體如下：

[root@mydocker yum.repos.d/etc/resolv.conf ]# cat /etc/resolv.conf 
nameserver 8.8.8.8

驗證：

[root@mydocker network-scripts]# wget http://mirrors.163.com/.help/CentOS7-Base-163.repo
--2016-10-01 09:44:02--  http://mirrors.163.com/.help/CentOS7-Base-163.repo
正在解析主機 mirrors.163.com (mirrors.163.com)... 123.58.173.186, 123.58.173.185
正在串連 mirrors.163.com (mirrors.163.com)|123.58.173.186|:80... 已串連。
已發出 HTTP 要求，正在等待回應... 200 OK
長度：1572 (1.5K) [application/octet-stream]
正在儲存至: “CentOS7-Base-163.repo”


100%[=====================================================================================================================================================>] 1,572       --.-K/s 用時 0s      


2016-10-01 09:44:02 (190 MB/s) - 已儲存 “CentOS7-Base-163.repo” [1572/1572])

可以看到已經將163的yum源下載下來了。