yum install 报错_yum install alien -y loaded plugins: fastestmirror

如下：

Loaded plugins: fastestmirror, langpacks
Loading mirror speeds from cached hostfile
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; Unknown error"
 
 
 One of the configured repositories failed (Unknown),
 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

ping了一下，发现连不上网啊 

[root@localhost /]# ping 114.114.114.114
connect: Network is unreachable
[root@localhost /]# ping www.baidu.com
ping: www.baidu.com: Name or service not known

重新移除后，再添加 ：

可以上网了

试了一下yum install能用了