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 all
yum 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～～