在网上看到的解决方法，故保存于此。

问题：Loaded plugins: fastestmirror Determining fastest mirrors YumRepo Error:
All mirror URLs are not using ftp,http[s] or file. /Eg. removing
mirrorlist with no valid mirrors: /var/cache/yum/addons/mirrorlist.txt
Error: Cannot find a valid baseurl for repo: addons

解决方法：vim/var/cache/yum/base/mirrorlist.txt

内容：http://mirrors.163.com/centos/5.7/os/x86_64/
http://centos.ustc.edu.cn/centos/5.7/os/x86_64/
http://mirror.neu.edu.cn/centos/5.7/os/x86_64/
http://mirrors.ta139.com/centos/5.7/os/x86_64/
@L_502_4@
http://ftp.tc.edu.tw/Linux/CentOS/5.7/os/x86_64/
http://ftp.isu.edu.tw/pub/Linux/CentOS/5.7/os/x86_64/
http://ftp.stu.edu.tw/Linux/CentOS/5.7/os/x86_64/
http://ftp.twaren.net/Linux/CentOS/5.7/os/x86_64/
http://ftp.cs.pu.edu.tw/Linux/CentOS/5.7/os/x86_64/
http://mirror01.idc.hinet.net/CentOS/5.7/os/x86_64/
http://centos.mirror.cdnetworks.com/5.7/os/x86_64/
http://centos.tt.co.kr/5.7/os/x86_64/
http://data.nicehosting.co.kr/os/CentOS/5.7/os/x86_64/
http://mirror.khlug.org/centos/5.7/os/x86_64/
http://mirror.yongbok.net/centos/5.7/os/x86_64/
http://ftp.daum.net/centos/5.7/os/x86_64/
http://mirror.nus.edu.sg/centos/5.7/os/x86_64/
http://mirror.averse.net/centos/5.7/os/x86_64/
http://mirrors.sin1.sg.voxel.net/centos/5.7/os/x86_64/

vim/var/cache/yum/updates/mirrorlist.txt

内容：

http://mirror.neu.edu.cn/centos/5.7/updates/x86_64/
http://mirrors.ta139.com/centos/5.7/updates/x86_64/
@L_301_22@
http://centos.ustc.edu.cn/centos/5.7/updates/x86_64/
http://ftp.stu.edu.tw/Linux/CentOS/5.7/updates/x86_64/
http://mirror01.idc.hinet.net/CentOS/5.7/updates/x86_64/
http://ftp.tc.edu.tw/Linux/CentOS/5.7/updates/x86_64/
http://ftp.isu.edu.tw/pub/Linux/CentOS/5.7/updates/x86_64/
http://ftp.cs.pu.edu.tw/Linux/CentOS/5.7/updates/x86_64/
http://ftp.daum.net/centos/5.7/updates/x86_64/
http://mirror.khlug.org/centos/5.7/updates/x86_64/
http://data.nicehosting.co.kr/os/CentOS/5.7/updates/x86_64/
http://centos.tt.co.kr/5.7/updates/x86_64/
http://mirror.averse.net/centos/5.7/updates/x86_64/
ftp://ftp.oss.eznetsols.org/linux/centos/5.7/updates/x86_64/
http://mirror.nus.edu.sg/centos/5.7/updates/x86_64/
http://mirrors.sin1.sg.voxel.net/centos/5.7/updates/x86_64/
http://centos.vr-zone.com/5.7/updates/x86_64/
http://rsync.atworks.co.jp/centos/5.7/updates/x86_64/
http://ftp.nara.wide.ad.jp/pub/Linux/centos/5.7/updates/x86_64/

vim /var/cache/yum/addons/mirrorlist.txt

内容：

http://dl.fedoraproject.org/pub/epel/6/x86_64/

vim/var/cache/yum/extras/mirrorlist.txt

内容：

http://centos.ustc.edu.cn/centos/5.7/extras/x86_64/
http://mirrors.stuhome.net/centos/5.7/extras/x86_64/
http://mirror.neu.edu.cn/centos/5.7/extras/x86_64/
http://mirrors.ta139.com/centos/5.7/extras/x86_64/
http://ftp.cs.pu.edu.tw/Linux/CentOS/5.7/extras/x86_64/
http://ftp.stu.edu.tw/Linux/CentOS/5.7/extras/x86_64/
http://ftp.tc.edu.tw/Linux/CentOS/5.7/extras/x86_64/
http://ftp.isu.edu.tw/pub/Linux/CentOS/5.7/extras/x86_64/
http://mirror01.idc.hinet.net/CentOS/5.7/extras/x86_64/
http://data.nicehosting.co.kr/os/CentOS/5.7/extras/x86_64/
http://mirror.khlug.org/centos/5.7/extras/x86_64/
http://ftp.daum.net/centos/5.7/extras/x86_64/
http://centos.tt.co.kr/5.7/extras/x86_64/
http://centos.vr-zone.com/5.7/extras/x86_64/
http://mirror.averse.net/centos/5.7/extras/x86_64/
http://mirrors.sin1.sg.voxel.net/centos/5.7/extras/x86_64/
ftp://ftp.oss.eznetsols.org/linux/centos/5.7/extras/x86_64/
http://mirror.nus.edu.sg/centos/5.7/extras/x86_64/
http://ftp.yz.yamagata-u.ac.jp/pub/linux/centos/5.7/extras/x86_64/
http://ftp.jaist.ac.jp/pub/Linux/CentOS/5.7/extras/x86_64/

若仍不能使用,在root用户下 #yum clean all //清除RPM

#yum update //更新下载即可，要联网。。。。