我正在尝试在CentOS上安装软件包，但是当我运行“ yum”命令时，它将引发错误。没有Internet连接无法正常工作。我尝试安装ntp并安装mysql-connector-java，但问题仍然存在。
错误：
[root#localhost ~]# yum install ntp
或
[root#localhost ~]# yum install mysql-connector-java
Loaded plugins: fastestmirror
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
尝试使用本地安装：
yum localinstall mysql-connector-java.1.8......rpm
并且请确保您满足此软件包的所有要求。并且文件mysql-connector-java.1.8......rpm应该在本地可用