由於我是用的系統是Centos 5.11以停止更新很多年，故此yum也不能用，找了很多方法，最終yum能穩定的運行在Centos5.11上，下面開始一一講解步驟：
1：首先更新yum源
地址：http://vault.centos.org/
網站是有各個版本鏡像的，所以 通過lsb_release -a查詢下，系統版本如圖
下面是我的yum源完整版本，下面會說出具體針對系統版本進行修改yum源方法：
vim /etc/yum.repos.d/Centos-Base.repo
# CentOS-Base.repo # # The mirror system uses the connecting IP address of the client and the # update status of each mirror to pick mirrors that are updated to and # geographically close to the client. You should use this for CentOS updates # unless you are manually picking other mirrors. # # If the mirrorlist= does not work for you, as a fall back you can try the # remarked out baseurl= line instead. # # [base] name=CentOS-$releasever - Base baseurl=http://vault.centos.org/5.11/os/x86_64/ gpgcheck=1 gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-5 #released updates [updates] name=CentOS-$releasever - Updates baseurl=http://vault.centos.org/5.11/os/x86_64/ gpgcheck=1 gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-5 #packages used/produced in the build but not released [addons] name=CentOS-$releasever - Addons baseurl=http://vault.centos.org/5.11/os/x86_64/ gpgcheck=1 gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-5 #additional packages that may be useful [extras] name=CentOS-$releasever - Extras baseurl=http://vault.centos.org/5.11/os/x86_64/ gpgcheck=1 gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-5 #additional packages that extend functionality of existing packages [centosplus] name=CentOS-$releasever - Plus baseurl=http://vault.centos.org/5.11/os/x86_64/ gpgcheck=1 enabled=0 gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-5 #contrib - packages by Centos Users [contrib] name=CentOS-$releasever - Contrib baseurl=http://vault.centos.org/5.11/os/x86_64/ gpgcheck=1 enabled=0 gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-5
注：如果你的版本是5.10（舉例說明），打開此網站，http://vault.centos.org，根據上述地址http://vault.centos.org/5.11/os/x86_64/來進行修改，比如系統是5.10的話，是x86_64的，我們可以修改成http://vault.centos.org/5.10/os/x86_64/，修改完成后，瀏覽器打開輸入地址，看看是不是可以顯示出以下頁面：
如果顯示出上述頁面，那根據我上面的5.11版本的Centos源把baseurl=http://vault.centos.org/5.11/os/x86_64/ 修改成 baseurl=http://vault.centos.org/5.10/os/x86_64/（是上述文件內容中，所有http://vault.centos.org/5.11/os/x86_64/地址），即可
修改完成后，保存，使用如下命令進行測試
yum clean all
yum makecache
測試成功后，可用yum進行安裝、卸載軟件