[root@xiniu nginx-1.10.2]# yum update
已加载插件：fastestmirror, langpacks
base                                                                                                                  | 3.6 kB  00:00:00     
extras                                                                                                                | 3.4 kB  00:00:00     
http://people.centos.org/tru/devtools-2/7/x86_64/RPMS/repodata/repomd.xml: [Errno 14] HTTPS Error 404 - Not Found
正在尝试其它镜像。
To address this issue please refer to the below wiki article 

https://wiki.centos.org/yum-errors

If above article doesn't help to resolve this issue please use https://bugs.centos.org/.



 One of the configured repositories failed (testing 2 devtools for CentOS 7),
 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=testing-devtools-2-centos-7 ...

     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 testing-devtools-2-centos-7
        or
            subscription-manager repos --disable=testing-devtools-2-centos-7

     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=testing-devtools-2-centos-7.skip_if_unavailable=true

failure: repodata/repomd.xml from testing-devtools-2-centos-7: [Errno 256] No more mirrors to try.
http://people.centos.org/tru/devtools-2/7/x86_64/RPMS/repodata/repomd.xml: [Errno 14] HTTPS Error 404 - Not Found

解决

cd  /etc/yum.repos.d

修改devtools-2.repo后缀名

修改后

执行：

[root@xiniu yum.repos.d]# yum clean all
已加载插件：fastestmirror, langpacks
正在清理软件源： base extras updates
Cleaning up everything
Maybe you want: rm -rf /var/cache/yum, to also free up space taken by orphaned data from disabled or removed repos
[root@xiniu yum.repos.d]# yum makecache

这样就解决问题了