yum install lrzsz -y 后报错

[root@localhost ~]# yum install lrzsz -y
已加载插件：fastestmirror

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

按照视频运行yum install lrzsz -y后出现这些文字，按照文字说明复制后，出现以下语句

[root@localhost ~]# yum --disablerepo= ...
-bash: repoid: 没有那个文件或目录

[root@localhost ~]# yum-config-manager --disable
-bash: 未预期的符号 `newline' 附近有语法错误

百度了许多帖子，但是按照里面的方法却还是不成功，请求帮助。