centos5†

vi /etc/yum.conf

proxy=http://proxy.jp:port 

vi /etc/wgetrc

http_proxy=http://proxy.jp:port/ 
ftp_proxy=http://proxy.jp:port/

useradd user -g users
wget http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-5
mv RPM-GPG-KEY-CentOS-5 /usr/share/doc/centos-release-5/RPM-GPG-KEY
rpm --import /usr/share/doc/centos-release-5/RPM-GPG-KEY
yum update

参考†

http://www.kfactory.net/?p=833