在centOS中更新yum 的资源和新的依赖时，报：Cannot find a valid baseurl for repo: base/7/x86_64
报错内容：
[root@localhost ~]# yum update 已加载插件：fastestmirror Could not retrieve mirrorlist http://mirrorlist.centos.org/?release=7&arch=x86_64&repo=os&infra=stock error was 14: curl#6 - "Could not resolve host: mirrorlist.centos.org; 未知的名称或服务"One of the configured repositories failed (未知),and yum doesn't have enough cached data to continue. At this point the onlysafe thing yum can do is fail. There are a few ways to work "fix" this:1. Contact the upstream for the repository and get them to fix the problem.2. Reconfigure the baseurl/etc. for the repository, to point to a workingupstream. This is most often useful if you are using a newerdistribution release than is supported by the repository (and thepackages for the previous distribution release still work).3. Disable the repository, so yum won't use it by default. Yum will then just ignore the repository until you permanently enable it again or use--enablerepo for temporary usage:yum-config-manager --disable <repoid>4. Configure the failing repository to be skipped, if it is unavailable.Note that yum will try to contact the repo. when it runs most commands,so will have to try and fail each time (and thus. yum will be be muchslower). If it is a very temporary problem though, this is often a nicecompromise:yum-config-manager --save --setopt=<repoid>.skip_if_unavailable=trueCannot find a valid baseurl for repo: base/7/x86_64
原因是在国内无法正常访问国外的网络，如能正常ping通百度。无法ping www.google.com ping通一样。因此无法正常更新yum的镜像。
可以使用国内的其他镜像：如阿里云的镜像
1、备份/etc/yum.repos.d 目录
cp -r /etc/yum.repos.d /etc/yum.repos.d.backup
2、重新编辑/etc/yum.repos.d/CentOS-Base.repo 的内容信息，如下:
# 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-$releasever - Base - mirrors.aliyun.com baseurl=http://mirrors.aliyun.com/centos/$releasever/os/$basearch/ gpgcheck=1 gpgkey=http://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-7 [updates] name=CentOS-$releasever - Updates - mirrors.aliyun.com baseurl=http://mirrors.aliyun.com/centos/$releasever/updates/$basearch/ gpgcheck=1 gpgkey=http://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-7 [extras] name=CentOS-$releasever - Extras - mirrors.aliyun.com baseurl=http://mirrors.aliyun.com/centos/$releasever/extras/$basearch/ gpgcheck=1 gpgkey=http://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-7 [centosplus] name=CentOS-$releasever - Plus - mirrors.aliyun.com baseurl=http://mirrors.aliyun.com/centos/$releasever/centosplus/$basearch/ gpgcheck=1 enabled=0 gpgkey=http://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-7
3、清除yum缓存并重新构建
yum clean all
yum makecache
4、然后在重新更新yum
yum update
就可以正常的更新yum的信息了。
