Como eu removo o el7 e seus pacotes no CentOS 6.9?

Question

Estou tentando instalar o Centreon do ssh e recebi este erro:

Error: Package: centreon-clib-1.4.2-3.el7.centos.x86_64 (centreon-stable)
   Requires: libstdc++.so.6(GLIBCXX_3.4.15)(64bit)
Error: Package: centreon-connector-ssh-1.1.2-3.el7.centos.x86_64 (centreon-stable)
   Requires: libstdc++.so.6(GLIBCXX_3.4.15)(64bit)
Error: Package: centreon-connector-ssh-1.1.2-3.el7.centos.x86_64 (centreon-stable)
   Requires: libc.so.6(GLIBC_2.14)(64bit)
Error: Package: centreon-clib-1.4.2-3.el7.centos.x86_64 (centreon-stable)
   Requires: libc.so.6(GLIBC_2.15)(64bit)
You could try using --skip-broken to work around the problem You could try running: rpm -Va --nofiles --nodigest

Como corrigir esse erro?