log查看：
sudo journalctl -fu docker.service
证书生成参考：
https://docs.docker.com/engine/security/https/
vi /lib/systemd/system/docker.service:
[Unit]
Description=Docker Application Container Engine
Documentation=https://docs.docker.com
After=network.target docker.socket
Requires=docker.socket
[Service]
Type=notify
# the default is not to use systemd for cgroups because the delegate issues still
# exists and systemd currently does not support the cgroup feature set required
# for containers run by docker
#ExecStart=/usr/bin/docker daemon --registry-mirror=http://3cda3ca9.m.daocloud.io -H fd://
#ExecStart=/usr/bin/docker daemon --registry-mirror=http://3cda3ca9.m.daocloud.io --insecure-registry 42.62.101.83:5000 -H fd://
#$OPTIONS $DOCKER_STORAGE_OPTIONS
#ExecStart=/usr/bin/docker daemon --registry-mirror=http://3cda3ca9.m.daocloud.io -H fd:// -H tcp://0.0.0.0:2375
ExecStart=/usr/bin/docker daemon --tlsverify --tlscacert=/root/openssl/ca.pem --tlscert=/root/openssl/server-cert.pem --tlskey=/root/openssl/server-key.pem --registry-mirror=http://3cda3ca9.m.daocloud.io -H tcp://0.0.0.0:2376
MountFlags=slave
LimitNOFILE=1048576
LimitNPROC=1048576
LimitCORE=infinity
TimeoutStartSec=0
# set delegate yes so that systemd does not reset the cgroups of docker containers
Delegate=yes
[Install]
WantedBy=multi-user.target
运行命令重启docker：
systemctl daemon-reload
service docker restart
Centos 7 Docker配置secure remote api
原文：http://www.cnblogs.com/flasheryu/p/5750401.html