两台相同操作的系统在配置本地yum源的时候一台配置正常，一台异常，弄了半天也没找出原因，最后把原来默认的yum源配置文件直接rm解决。
[root@rac02 ~]# cat /etc/redhat-release
Red Hat Enterprise Linux Server release 7.3 (Maipo)
在/etc/yum.repos.d/目录新建了一个mnt.repo的本地yum源，验证时报错：
[root@rac02 yum.repos.d]# ls
mnt.repo public-yum-ol7.repo
[root@rac1 Desktop]# yum makecache
Loaded plugins: langpacks, ulninfo
Repository ol7_latest is listed more than once in the configuration
http://yum.oracle.com/repo/OracleLinux/OL7/UEKR4/x86_64/repodata/repomd.xml: [Errno 14] curl#6 - "Could not resolve host: yum.oracle.com; Unknown error"
Trying other mirror.
One of the configured repositories failed (Latest Unbreakable Enterprise Kernel Release 4 for Oracle Linux 7Server (x86_64)),
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=ol7_UEKR4 ...
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 ol7_UEKR4
or
subscription-manager repos --disable=ol7_UEKR4
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=ol7_UEKR4.skip_if_unavailable=true
failure: repodata/repomd.xml from ol7_UEKR4: [Errno 256] No more mirrors to try. http://yum.oracle.com/repo/Oracl ... epodata/repomd.xml: [Errno 14] curl#6 - "Could not resolve host: yum.oracle.com; Unknown error"
解决办法：
[root@rac02 yum.repos.d]# rm public-yum-ol7.repo
[root@rac02 yum.repos.d]# ls
mnt.repo