1.備份
mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.backup
2.下載新的CentOS-Base.repo 到/etc/yum.repos.d/
wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-6.repo
3.
yum makecache

GDB的安裝

yum list //顯示服務器所有可以安裝的軟件
yum list | grep gdb //顯示和gdb有關的
yum list | grep mysql