system version
[root@bogon ~]# cat /etc/redhat-release
CentOS Linux release 7.1.1503 (Core)
docker version
[root@bogon ~]# docker --version
Docker version 1.7.1, build 446ad9b/1.7.1
error message
[root@bogon ~]# docker pull dl.dockerpool.com:5000/ubuntu:12.04
Error response from daemon: invalid registry endpoint https://dl.dockerpool.com:5000/v0/: unable to ping registry endpoint https://dl.dockerpool.com:5000/v0/
v2 ping attempt failed with error: Get https://dl.dockerpool.com:5000/v2/: tls: oversized record received with length 28012
v1 ping attempt failed with error: Get https://dl.dockerpool.com:5000/v1/_ping: tls: oversized record received with length 28012. If this private registry supports only HTTP or HTTPS with an unknown CA certificate, please add `--insecure-registry dl.dockerpool.com:5000` to the daemon's arguments. In the case of HTTPS, if you have access to the registry's CA certificate, no need for the flag; simply place the CA certificate at /etc/docker/certs.d/dl.dockerpool.com:5000/ca.crt
[root@bogon ~]#
Solution:
Modify the /etc/sysconfig/docker file and add the following information
OPTIONS='--selinux-enabled --insecure-registry dl.dockerpool.com:5000'
Restart the docker service and download again
[root@bogon ~]# systemctl restart docker.service
[root@bogon ~]# docker pull dl.dockerpool.com:5000/ubuntu:12.04
Trying to pull repository dl.dockerpool.com:5000/ubuntu ...
0b310e6bf058: Download complete
511136ea3c5a: Download complete
5f18d94c3eca: Download complete
53db23c604fd: Download complete
9f045ea36057: Download complete
d03a1a9d7555: Download complete
30868777f275: Download complete
Status: Downloaded newer image for dl.dockerpool.com:5000/ubuntu:12.04