執行 docker run 時遇到如下WARNING：

[root@etcd1 volumes]# docker run -d -p 8080:80 -v /tmp/test_mount httpd
Unable to find image ‘httpd:latest‘ locally
Trying to pull repository docker.io/library/httpd ... 
sha256:72f2b4aa99235509146bd12054d1a93c1c869ba60212d21729118c93ca4305d3: Pulling from docker.io/library/httpd
3d77ce4481b1: Pull complete 
73674f4d9403: Pull complete 
d266646f40bd: Pull complete 
ce7b0dda0c9f: Pull complete 
01729050d692: Pull complete 
014246127c67: Pull complete 
7cd2e04cf570: Pull complete 
Digest: sha256:72f2b4aa99235509146bd12054d1a93c1c869ba60212d21729118c93ca4305d3
Status: Downloaded newer image for docker.io/httpd:latest
WARNING: IPv4 forwarding is disabled. Networking will not work.
 

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查看 IPv4 forwarding 啟用情況

[root@etcd1 volumes]# sysctl net.ipv4.ip_forward
net.ipv4.ip_forward = 0

解決方案：

[root@etcd1 volumes]# echo net.ipv4.ip_forward=1 >> /usr/lib/sysctl.d/00-system.conf
[root@etcd1 volumes]# systemctl restart network

查看是否修改成功：

[root@etcd1 volumes]# sysctl net.ipv4.ip_forward                       
net.ipv4.ip_forward = 1　

重啟docker服務：

[root@etcd1 volumes]# systemctl restart docker

完成！

docker run 報錯——WARNING: IPv4 forwarding is disabled. Networking will not work.