[CentOS] yum install failiure - CentOS-7 - Base

Sun Apr 19 18:44:43 UTC 2015
Sarogahtyp <sarogahtyp at web.de>

I have a running  CentOS 6.5 64-bit system running and i like to have a 
CentOS 7 chrooted system inside.
Ive done that chroot environment as described in

Now my problem ist that yum is not working as i suggested:

bash-4.2# yum install sudo
Geladene Plugins: fastestmirror
http://mirror.centos.org/centos/7/os/i386/repodata/repomd.xml: [Errno 14] 
HTTP Error 404 - Not Found
Anderer Spiegelserver wird versucht.

 One of the configured repositories failed (CentOS-7 - Base),
 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 

     2. Reconfigure the baseurl/etc. for the repository, to point to a 
        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. Disable the repository, so yum won't use it by default. Yum will 
        just ignore the repository until you permanently enable it again or 
        --enablerepo for temporary usage:

            yum-config-manager --disable base

     4. Configure the failing repository to be skipped, if it is 
        Note that yum will try to contact the repo. when it runs most 
        so will have to try and fail each time (and thus. yum will be be 
        slower). If it is a very temporary problem though, this is often a 

            yum-config-manager --save --setopt=base.skip_if_unavailable=true

failure: repodata/repomd.xml from base: [Errno 256] No more mirrors to try.
http://mirror.centos.org/centos/7/os/i386/repodata/repomd.xml: [Errno 14] 
HTTP Error 404 - Not Found

any ideas ?