centos 7使用yum报错“Could not resolve host: mirrorlist.centos.org； 未知的错误“

centos使用yum -y install报错"Could not resolve host: mirrorlist.centos.org; 未知的错误"
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; 未知的错误”

One of the configured repositories failed (未知),
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. Run the command with the repository temporarily disabled
        yum --disablerepo= ...

 4. Disable the repository permanently, 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 
    or
        subscription-manager repos --disable=

 5. 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=.skip_if_unavailable=true

googel了一下这个错误，发现报错原因是“本机无法连接网络的网络设置”的原因。

于是参照“How to Setup network on centos 7”这篇博文，配置了下DHPC，最终解决了这个error。

原因：linux虚拟机网络不通设置网络

查看网络情况
ip addr

以上是未分配ip

一： 设置vm ip自动分配

1.登录虚拟机：

vi /etc/sysconfig/network-scripts/ifcfg-ens33 

设置：ONBOOT=yes

设置vm :右击单机设置=》网络编辑=>设置桥接模式=》确定

设置完重启网络：

service network restart

重新查看ip:

ip addr

以上就是完成网络自动分配设置

二 yum 安装jdk

下载jdk 1.8

yum install -y java-1.8.0-openjdk java-1.8.0-openjdk-devel
或者：
yum -y list java*

查看jdk 版本：

java -version

设置环境变量：

vi /etc/profile

添加环境变量：

# set java environment  
JAVA_HOME=/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.181-3.b13.el7_5.x86_64
PATH=$PATH:$JAVA_HOME/bin  
CLASSPATH=.:$JAVA_HOME/lib/dt.jar:$JAVA_HOME/lib/tools.jar  
export JAVA_HOME  CLASSPATH  PATH

重新加载环境变量配置：

source  /etc/profile

查看环境变量设置

echo $JAVA_HOME

echo $PATH

echo $PATH

echo $CLASSPATH

完成jdk