[root@localhost ~]# yum -y install gcc
Loaded plugins: katello, product-id, security, subscription-manager
Updating certificate-based repositories.
Unable to read consumer identity
Setting up Install Process
No package gcc available.
Nothing to do

[root@localhost~]# wget http://mirrors.163.com/.help/CentOS6-Base-163.repo
--2015-10-09 14:33:10-- http://mirrors.163.com/.help/CentOS6-Base-163.repo
Resolving mirrors.163.com... 123.58.173.186,123.58.173.185
Connecting to mirrors.163.com|123.58.173.186|:80...connected.
HTTP request sent, awaiting response... 200 OK
Length: 2341 (2.3K) [application/octet-stream]
Saving to: `CentOS6-Base-163.repo'
100%2,341    --.-K/s  in 0s   
2015-10-09 14:33:22 (108 MB/s) -`CentOS6-Base-163.repo' saved [2341/2341]

[root@localhost~]# mv CentOS6-Base-163.repo /etc/yum.repos.d/
*** 把$releasever替换成6
[root@localhost yum.repos.d]# sed -i 's#$releasever#6#g' ./CentOS6-Base-163.repo

[root@localhost yum.repos.d]# yum clean all
Loaded plugins: katello, product-id, security, subscription-manager
Updating certificate-based repositories.
Unable to read consumer identity
Cleaning up Everything

[root@localhost yum.repos.d]# yum makecache
Loaded plugins: katello, product-id, security, subscription-manager
Updating certificate-based repositories.
Unable to read consumer identity
addons                                                 | 1.9 kB   00:00   
addons/filelists_db                                          | 570 B   00:00   
........
........
base                                                        3667/3667
base                                                        3667/3667
base                                                        3667/3667
Metadata Cache Created

[root@localhost ~]# yum search gcc |grep --color '^gcc'
gcc.x86_64 : Various compilers (C, C++, Objective-C, Java, ...)
gcc-c++.x86_64 : C++ support for GCC
gcc-gfortran.x86_64 : Fortran 95 support
gcc-gnat.x86_64 : Ada 95 support for GCC
gcc-java.x86_64 : Java support for GCC
gcc-objc++.x86_64 : Objective-C++ support for GCC
gcc-objc.x86_64 : Objective-C support for GCC
gcc44.x86_64 : GNU Compiler Collection version 4.4
gcc44-c++.x86_64 : C++ support for GCC version 4.4
gcc44-gfortran.x86_64 : Fortran support for GCC 4.4

[root@localhost yum.repos.d]# yum -y install gcc