yum is an interactive, rpm based, package manager.（yum是一个包的管理器）
yum可以简化系统软件更新的工作。为了保证更新的持续进行，通常都会提供多个mirror（镜像）地址供下载使用，但由于存在地域问题，从不同的镜像下载速度差异很大。选择从适合的镜像下载软件包，会极大的影响更新速度。以CentOS为例，可使用一个叫fastestmirror的插件，让yum在更新时先根据ping值进行判断，然后从最快响应的地址下载。
这里介绍fastermirror.
【安装配置】
从CentOS5.0开始fastermirror就默认安装了，我们这里主要介绍配置
1.安装
yum install yum-plugin-fastestmirror
2.验证
[root@pandaVM script]# [root@pandaVM script]# yum search yum-plugin-fastestmirror Loaded plugins: fastestmirror, refresh-packagekit, security Loading mirror speeds from cached hostfile
3.配置
fastestmirror里面的enable=1
[root@pandaVM script]# cat /etc/yum/pluginconf.d/fastestmirror.conf [main] enabled=1 verbose=0 always_print_best_host = true socket_timeout=3 # Relative paths are relative to the cachedir (and so works for users as well # as root). hostfilepath=timedhosts.txt maxhostfileage=10 maxthreads=15 #exclude=.gov, facebook #include_only=.nl,.de,.uk,.ie
yum.conf里面的plugins=1
[root@pandaVM script]# cat /etc/yum.conf [main] cachedir=/var/cache/yum/$basearch/$releasever keepcache=0 debuglevel=2 logfile=/var/log/yum.log exactarch=1 obsoletes=1 gpgcheck=1 plugins=1 installonly_limit=5 bugtracker_url=http://bugs.centos.org/set_project.php?project_id=16&ref=http://bugs.centos.org/bug_report_page.php?category=yum distroverpkg=centos-release # This is the default, if you make this bigger yum won't see if the metadata # is newer on the remote and so you'll "gain" the bandwidth of not having to # download the new metadata and "pay" for it by yum not having correct # information. # It is esp. important, to have correct metadata, for distributions like # Fedora which don't keep old packages around. If you don't like this checking # interupting your command line usage, it's much better to have something # manually check the metadata once an hour (yum-updatesd will do this). # metadata_expire=90m # PUT YOUR REPOS HERE OR IN separate files named file.repo # in /etc/yum.repos.d
[root@localhost ~]# cat /var/cache/yum/timedhosts.txt mirrors.cug.edu.cn 0.0390000343323 mirror.bit.edu.cn 0.417052030563 mirrors.hustunique.com 0.0460698604584 mirrors.hust.edu.cn 0.189108133316 mirrors.yun-idc.com 0.0331869125366 mirrors.btte.net 0.0333859920502 mirrors.skyshe.cn 0.0205020904541 mirrors.163.com 0.0148000717163 mirrors.aliyun.com 0.0303590297699 mirror.neu.edu.cn 0.0602879524231 www7.atomicorp.com 0.618637084961 mirror.bit.edu.cn 0.525043010712 centos.ustc.edu.cn 0.317930936813 mirrors.163.com 0.0135080814362 mirrors.tuna.tsinghua.edu.cn 0.193212032318 www2.atomicorp.com 0.415390014648 mirrors.skyshe.com 0.329003095627 atomic.mirror.uber.com.au 1.13594508171 www3.atomicorp.com 0.425523996353 www6.atomicorp.com 0.45193195343 mirrors.stuhome.net 0.592149019241 mirrors.btte.net 0.164302110672 mirrors.neusoft.edu.cn 0.478916883469 mirrors.grandcloud.cn 0.243366956711 www5.atomicorp.com 0.452031850815 mirrors.hustunique.com 0.24665594101 mirrors.yun-idc.com 0.147311925888 www4.atomicorp.com 99999999999 mirror.neu.edu.cn 0.158205032349
【问题】
遇到一个yum在执行的时候一直卡在寻找最佳mirror地方，我们可以在mirrorlist里面找几个地址ping一下，发现都不通。其实是域名解析有问题。
【参考】
http://bbs.51cto.com/thread-549433-1.html
http://blog.sina.com.cn/s/blog_7e513d7e01015j9b.html