一. 今天登录服务器的时候，误把yum所在的cache文件夹中的文件删除掉了，导致yum不能够使用，解决的方法：
显示错误如下：
不知道什么时候把mirrors.txt文件给去掉了。
后来查了一下有这么一串。
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
后来查了一下有这么一串。
1 1./var/cache/yum/base/mirrorlist.txt url: 2 http://mirrors.163.com/centos/5.7/os/x86_64/ 3 http://centos.ustc.edu.cn/centos/5.7/os/x86_64/ 4 http://mirror.neu.edu.cn/centos/5.7/os/x86_64/ 5 http://mirrors.ta139.com/centos/5.7/os/x86_64/ 6 http://ftp.nsysu.edu.tw/CentOS/5.7/os/x86_64/ 7 http://ftp.tc.edu.tw/Linux/CentOS/5.7/os/x86_64/ 8 http://ftp.isu.edu.tw/pub/Linux/CentOS/5.7/os/x86_64/ 9 http://ftp.stu.edu.tw/Linux/CentOS/5.7/os/x86_64/ 10 http://ftp.twaren.net/Linux/CentOS/5.7/os/x86_64/ 11 http://ftp.cs.pu.edu.tw/Linux/CentOS/5.7/os/x86_64/ 12 http://mirror01.idc.hinet.net/CentOS/5.7/os/x86_64/ 13 http://centos.mirror.cdnetworks.com/5.7/os/x86_64/ 14 http://centos.tt.co.kr/5.7/os/x86_64/ 15 http://data.nicehosting.co.kr/os/CentOS/5.7/os/x86_64/ 16 http://mirror.khlug.org/centos/5.7/os/x86_64/ 17 http://mirror.yongbok.net/centos/5.7/os/x86_64/ 18 http://ftp.daum.net/centos/5.7/os/x86_64/ 19 http://mirror.nus.edu.sg/centos/5.7/os/x86_64/ 20 http://mirror.averse.net/centos/5.7/os/x86_64/ 21 http://mirrors.sin1.sg.voxel.net/centos/5.7/os/x86_64/ 22 2./var/cache/yum/updates/mirrorlist.txt url: 23 http://mirror.neu.edu.cn/centos/5.7/updates/x86_64/ 24 http://mirrors.ta139.com/centos/5.7/updates/x86_64/ 25 http://mirrors.stuhome.net/centos/5.7/updates/x86_64/ 26 http://centos.ustc.edu.cn/centos/5.7/updates/x86_64/ 27 http://ftp.stu.edu.tw/Linux/CentOS/5.7/updates/x86_64/ 28 http://mirror01.idc.hinet.net/CentOS/5.7/updates/x86_64/ 29 http://ftp.tc.edu.tw/Linux/CentOS/5.7/updates/x86_64/ 30 http://ftp.isu.edu.tw/pub/Linux/CentOS/5.7/updates/x86_64/ 31 http://ftp.cs.pu.edu.tw/Linux/CentOS/5.7/updates/x86_64/ 32 http://ftp.daum.net/centos/5.7/updates/x86_64/ 33 http://mirror.khlug.org/centos/5.7/updates/x86_64/ 34 http://data.nicehosting.co.kr/os/CentOS/5.7/updates/x86_64/ 35 http://centos.tt.co.kr/5.7/updates/x86_64/ 36 http://mirror.averse.net/centos/5.7/updates/x86_64/ 37 ftp://ftp.oss.eznetsols.org/linux/centos/5.7/updates/x86_64/ 38 http://mirror.nus.edu.sg/centos/5.7/updates/x86_64/ 39 http://mirrors.sin1.sg.voxel.net/centos/5.7/updates/x86_64/ 40 http://centos.vr-zone.com/5.7/updates/x86_64/ 41 http://rsync.atworks.co.jp/centos/5.7/updates/x86_64/ 42 http://ftp.nara.wide.ad.jp/pub/Linux/centos/5.7/updates/x86_64/ 43 3./var/cache/yum/addons/mirrorlist.txt url: 44 http://mirror.centos.org/centos/5/addons/x86_64/ 45 4./var/cache/yum/extras/mirrorlist.txt url: 46 http://centos.ustc.edu.cn/centos/5.7/extras/x86_64/ 47 http://mirrors.stuhome.net/centos/5.7/extras/x86_64/ 48 http://mirror.neu.edu.cn/centos/5.7/extras/x86_64/ 49 http://mirrors.ta139.com/centos/5.7/extras/x86_64/ 50 http://ftp.cs.pu.edu.tw/Linux/CentOS/5.7/extras/x86_64/ 51 http://ftp.stu.edu.tw/Linux/CentOS/5.7/extras/x86_64/ 52 http://ftp.tc.edu.tw/Linux/CentOS/5.7/extras/x86_64/ 53 http://ftp.isu.edu.tw/pub/Linux/CentOS/5.7/extras/x86_64/ 54 http://mirror01.idc.hinet.net/CentOS/5.7/extras/x86_64/ 55 http://data.nicehosting.co.kr/os/CentOS/5.7/extras/x86_64/ 56 http://mirror.khlug.org/centos/5.7/extras/x86_64/ 57 http://ftp.daum.net/centos/5.7/extras/x86_64/ 58 http://centos.tt.co.kr/5.7/extras/x86_64/ 59 http://centos.vr-zone.com/5.7/extras/x86_64/ 60 http://mirror.averse.net/centos/5.7/extras/x86_64/ 61 http://mirrors.sin1.sg.voxel.net/centos/5.7/extras/x86_64/ 62 ftp://ftp.oss.eznetsols.org/linux/centos/5.7/extras/x86_64/ 63 http://mirror.nus.edu.sg/centos/5.7/extras/x86_64/ 64 http://ftp.yz.yamagata-u.ac.jp/pub/linux/centos/5.7/extras/x86_64/ 65 http://ftp.jaist.ac.jp/pub/Linux/CentOS/5.7/extras/x86_64/ 66 67 对应的把这些url拷贝到mirrorlist.txt文件中去就ok啦。
二.Linux中yum的配置：
执行yum的时候，报如下的错误：
Error Downloading Packages: openssl-devel-1.0.1e-16.el6_5.14.i686:failure: Packages/openssl-devel-1.0.1e-16.el6_5.14.i686.rpm base: [Errno 256] No more mirrors to try. openssl-devel-1.0.1e-16.el6_5.14.i686:failure: Packages/openssl-devel-1.0.1e-16.el6_5.14.i686.rpm base: [Errno 256] No more mirrors to try. openssl-devel-1.0.1e-16.el6_5.14.i686:failure: Packages/openssl-devel-1.0.1e-16.el6_5.14.i686.rpm base: [Errno 256] No more mirrors to try. openssl-devel-1.0.1e-16.el6_5.14.i686:failure: Packages/openssl-devel-1.0.1e-16.el6_5.14.i686.rpm from base: [Errno 256] No more mirrors to try.
解决的方法：
1 执行yum clean all 清除缓存目录下的软件包及旧的headers； 2 接着执行 yum list 重新列出所有已经安装和可以安装的软件包； 3 重新执行上述命令，发现yum编译成功； 4 注意：如果执行 yum list 报错，那就检查一下yum仓库是否有问题；并清除/etc/yum.repos.d/下多余.repo文件！
三. Centos更改yum源与更新系统
[1] 首先备份/etc/yum.repos.d/CentOS-Base.repo mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.backup [2] 进入yum源配置文件所在文件夹 [root@localhost yum.repos.d]# cd /etc/yum.repos.d/ [3] 下载163的yum源配置文件，放入/etc/yum.repos.d/(操作前请做好相应备份) [root@localhost yum.repos.d]# wget http://mirrors.163.com/.help/CentOS6-Base-163.repo [4] 运行yum makecache生成缓存 [root@localhost yum.repos.d]# yum makecache [5] 更新系统 [root@localhost yum.repos.d]# yum -y update