第一种方法:
yum源来自chinalinuxpub.com,用的是centos包,
下载地址:http://www.chinalinuxpub.com/yum.tgz
安装:
tarzxvfyum.tgz
cdyum
rpm-ivh*.rpm
rm-rf/etc/yum.repos.d/CentOS-Base.repo
vi/etc/yum.repos.d/as4-update.repo
加入：
#releasedupdates
[update]
name=RedHatEnterpriseASrelease4Updates
baseurl=http://ftp.chinalinuxpub.com/redhat/enterprise/updates/4AS/
gpgcheck=1
gpgkey=http://ftp.chinalinuxpub.com/redhat/enterprise/RPM-GPG-KEY-linuxpub
vi/etc/yum.repos.d/as4-base.repo
加入：
#releasedbase
[base]
name=RedHatEnterpriseASrelease4Updates
baseurl=http://ftp.chinalinuxpub.com/redhat/enterprise/os/i***/RedHat/
gpgcheck=1
gpgkey=http://ftp.chinalinuxpub.com/redhat/enterprise/RPM-GPG-KEY-linuxpub
然后就可以正常使用yum了.
第二种方法:利用CentOS的yum库升级RHELAS4
1.下载并安装yum-2.4.0-1.centos4.noarch.rpm文件，下载地址为：
ftp://ftp.pbone.net/mirror/ftp.centos.org/4.5/os/alpha/CentOS/RPMS/yum-2.4.2-1.centos4.noarch.rpm
2.修改或建立/etc/yum.repos.d/CentOS-Base.repo为如下内容：
[base]
name=CentOS-$releasever-Base
baseurl=http://ftp.riken.jp/Linux/caos/centos/4.5/os/$basearch/
gpgcheck=1
#releasedupdates
[update]
name=CentOS-$releasever-Updates
baseurl=http://ftp.riken.jp/Linux/caos/centos/4.5/updates/$basearch/
gpgcheck=1
#packagesused/producedinthebuildbutnotreleased
[addons]
name=CentOS-$releasever-Addons
baseurl=http://ftp.riken.jp/Linux/caos/centos/4.5/addons/$basearch/
gpgcheck=1
#additionalpackagesthatmaybeuseful
[extras]
name=CentOS-$releasever-Extras
baseurl=http://ftp.riken.jp/Linux/caos/centos/4.5/extras/$basearch/
gpgcheck=1
3.修改或建立/etc/yum.repos.d/dag.repo为如下内容：
[dag]
name=DagRPMRepositoryforRHEL4
baseurl=http://ftp.riken.jp/Linux/dag/redhat/el4/en/$basearch/dag/
enabled=1
gpgcheck=1
gpgkey=http://ftp.riken.jp/Linux/dag/packages/RPM-GPG-KEY.dag.txt
4.运行update:
yumupdate
5.升级：
yumupgrade
6.安装其它软件，例如：
yuminstallmplayer