centos7.0 yum doesn't work 输入yum 不起作用的解决办法

1. 将yum源更新为国内163yum源或阿里源

首先，将系统原有的yum源备份

cd /etc/yum.repos.d/

mv CentOS-Base.repo CentOS-Base.repo.backup

下载阿里云的yum源配置或163的yum源

wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo   注：阿里云yun源

wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.163.com/.help/CentOS7-Base-163.repo    注：网易yum源

然后重建缓存：

yum clean allyum makecache

若出错，并显示提示信息如下：

One of the configured repositories failed (Fedora 20 - x86_64 - Updates),
 and yum doesn't have enough cached data to continue. At this point the only
 safe 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 working
        upstream. This is most often useful if you are using a newer
        distribution release than is supported by the repository (and the
        packages 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 updates

     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 much
        slower). If it is a very temporary problem though, this is often a nice
        compromise:

            yum-config-manager --save --setopt=updates.skip_if_unavailable=true

解决办法：

sudo yum upgrade

之后会进行更新，y/d/n三个选项，不想更新的话选择n，回车

接着再执行yum makecache就成功啦！！！

使用yum install software-package也没问题哦～～