Upgrade docker on CentOS 7 Fix Failed to chown socket at step GROUP: No such process

To have the latest Docker, I first start from Docker's Official Guide: https://docs.docker.com/installation/centos/

wget https://get.docker.com/builds/Linux/x86_64/docker-latest -O docker
chmod +x ./docker
cp ./docker /usr/bin/docker

install the two unit files (service and socket) from the github repository to /etc/systemd/system.

systemctl start docker.socket
service docker start

But hold on, it doesn't work!

# service docker start
Redirecting to /bin/systemctl start  docker.service
A dependency job for docker.service failed. See 'journalctl -xn' for details.

Here is the error log:

# journalctl -xn
-- Logs begin at Tue 2014-12-30 13:07:53 EST, end at Tue 2014-12-30 13:25:23 EST. --
Dec 30 13:12:30 ITX kernel: ip_tables: (C) 2000-2006 Netfilter Core Team
Dec 30 13:22:53 ITX systemd[1]: Starting Cleanup of Temporary Directories...
-- Subject: Unit systemd-tmpfiles-clean.service has begun with start-up
-- Defined-By: systemd
-- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
--
-- Unit systemd-tmpfiles-clean.service has begun starting up.
Dec 30 13:22:53 ITX systemd[1]: Started Cleanup of Temporary Directories.
-- Subject: Unit systemd-tmpfiles-clean.service has finished start-up
-- Defined-By: systemd
-- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
--
-- Unit systemd-tmpfiles-clean.service has finished starting up.
--
-- The start-up result is done.
Dec 30 13:25:23 ITX systemd[1]: Starting Docker Socket for the API.
-- Subject: Unit docker.socket has begun with start-up
-- Defined-By: systemd
-- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
--
-- Unit docker.socket has begun starting up.
Dec 30 13:25:23 ITX systemd[1868]: Failed to chown socket at step GROUP: No such process
Dec 30 13:25:23 ITX systemd[1]: docker.socket control process exited, code=exited status=216
Dec 30 13:25:23 ITX systemd[1]: Failed to listen on Docker Socket for the API.
-- Subject: Unit docker.socket has failed
-- Defined-By: systemd
-- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
--
-- Unit docker.socket has failed.
--
-- The result is failed.
Dec 30 13:25:23 ITX systemd[1]: Dependency failed for Docker Application Container Engine.
-- Subject: Unit docker.service has failed
-- Defined-By: systemd
-- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
--
-- Unit docker.service has failed.
--
-- The result is dependency.
Dec 30 13:25:23 ITX systemd[1]: Unit docker.socket entered failed state.

My easy fix solution, install Docker from YUM first. Then replace the docker file with the latest download:

service docker stop
rm /etc/systemd/system/docker.*
cp ./docker /usr/bin/docker
service docker start

After restart it, everything works fine.
At this moment (Dec 30, 2014), the latest stable Docker is 1.4.1

To enable the service and socket in systemd:

# systemctl list-unit-files | grep docker
docker.service                         disabled
docker.socket                          disabled

# chkconfig docker on
Note: Forwarding request to 'systemctl enable docker.service'.
ln -s '/usr/lib/systemd/system/docker.service' '/etc/systemd/system/multi-user.target.wants/docker.service'

# systemctl list-unit-files|grep docker
docker.service                         enabled
docker.socket                          disabled

# systemctl enable docker.socket
ln -s '/usr/lib/systemd/system/docker.socket' '/etc/systemd/system/sockets.target.wants/docker.socket'

# systemctl list-unit-files|grep docker
docker.service                         enabled
docker.socket                          enabled

Thank you!