docker执行yum报错Could not resolve host: mirrorlist.centos.org

解决办法：

    -- 依次执行以下命令
	cd /etc/yum.repos.d/

    sed -i 's|#baseurl=http://mirror.centos.org|baseurl=http://vault.centos.org|g' /etc/yum.repos.d/CentOS-*

    sed -i 's/mirrorlist/#mirrorlist/g' /etc/yum.repos.d/CentOS-*

    yum update -y

    echo "export LC_ALL=en_US.utf8"  >>  /etc/profile

    echo "export LC_CTYPE=en_US.utf8"  >>  /etc/profile

    source /etc/profile
    yum install -y net-tools