Linux-yum报错

错误日志

已加载插件：fastestmirror, langpacks
Determining fastest mirrors
Could not retrieve mirrorlist http://mirrorlist.centos.org/?release=7&arch=x86_64&repo=os&infra=stock error was
14: curl#6 - "Could not resolve host: mirrorlist.centos.org; 未知的错误"


 One of the configured repositories failed (未知),
 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. Run the command with the repository temporarily disabled
            yum --disablerepo=<repoid> ...

     4. Disable the repository permanently, 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 <repoid>
        or
            subscription-manager repos --disable=<repoid>

     5. 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=<repoid>.skip_if_unavailable=true

Cannot find a valid baseurl for repo: base/7/x86_64

---

原因

问题原因是Linux的DNS设置错误

---

解决方法

1. 如下将目标值修改为114.114.114.114，
2. 重新启动网络服务
   
3. 测试之后问题依旧存在
4. 继续排查，ping自己的dns发现可以通，应该还是dns的问题
5. 尝试ping 8.8.8.8，成功
   
6. 尝试写入DNS文件8.8.8.8,测试失败
7. 最终删除ifconfig-en33文件，测试发现网络可以连接，但是执行域名 update有如下报错

已加载插件：fastestmirror, langpacks
Loading mirror speeds from cached hostfile
 * base: mirrors.163.com
 * extras: mirrors.163.com
 * updates: mirrors.163.com
base                                                                             | 3.6 kB  00:00:00     
file:///iso/repodata/repomd.xml: [Errno 14] curl#37 - "Couldn't open file /iso/repodata/repomd.xml"
正在尝试其它镜像。


 One of the configured repositories failed (dvd),
 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. Run the command with the repository temporarily disabled
            yum --disablerepo=dvd ...

     4. Disable the repository permanently, 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 dvd
        or
            subscription-manager repos --disable=dvd

     5. 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=dvd.skip_if_unavailable=true

failure: repodata/repomd.xml from dvd: [Errno 256] No more mirrors to try.
file:///iso/repodata/repomd.xml: [Errno 14] curl#37 - "Couldn't open file /iso/repodata/repomd.xml"

9. 根据文章（https://blog.youkuaiyun.com/cheng_jeff/article/details/123642069），排除该错误后，测试安装成功。