问题描述：

安装完docker后，运行docker build的时候，报错如下：

原因分析：

因配置的网络是使用特定虚拟机网络，需要开启网络转发配置

解决方案：

方法一

sudo vim /etc/sysctl.conf

#配置转发
net.ipv4.ip_forward=1

#重启服务，让配置生效
sudo systemctl restart network

#查看是否成功,如果返回为“net.ipv4.ip_forward = 1”则表示成功
sudo sysctl net.ipv4.ip_forward

方法二

[wherein@CentOS01 ~]$ cat /etc/sysctl.conf 
# sysctl settings are defined through files in 有以下三个文件包含的配置
# /usr/lib/sysctl.d/, /run/sysctl.d/, and /etc/sysctl.d/.
#
# Vendors settings live in /usr/lib/sysctl.d/.
# To override a whole file, create a new file with the same in
# /etc/sysctl.d/ and put new settings there. To override
# only specific settings, add a file with a lexically later
# name in /etc/sysctl.d/ and put new settings there.
#
# For more information, see sysctl.conf(5) and sysctl.d(5).

[root@CentOS01 wherein]# sudo echo "net.ipv4.ip_forward=1" >> /usr/lib/sysctl.d/00-system.conf