Cannot start docker daemon in CentOS7

To resolve this issue, one have to create a missing file: /usr/lib/systemd/system/docker.socket

[Unit]
Description=Docker Socket for the API
PartOf=docker.service

[Socket]
ListenStream=/var/run/docker.sock
SocketMode=0660
SocketUser=root
SocketGroup=docker

[Install]
WantedBy=sockets.target

Then run:

systemctl daemon-reload
systemctl start docker.socket
systemctl start docker

Then Docker will start. It looks like the install removes that file and doesn't replace it.

Simply try and install again docker, to see if the issue persists:

sudo yum install docker 

Then service docker start and docker info.