[root@localhost ~]# uname -r
3.10.0-327.10.1.el7.x86_64

sudo yum update

[root@localhost ~]# curl -sSL https://get.docker.com/ | sh 
+ sh -c 'sleep 3; yum -y -q install docker-engine'
Delta RPMs disabled because /usr/bin/applydeltarpm not installed.
warning: /var/cache/yum/x86_64/7/docker-main-repo/packages/docker-engine-selinux-1.10.3-1.el7.centos.noarch.rpm: Header V4 RSA/SHA512 Signature, key ID 2c52609d: NOKEY
Public key for docker-engine-selinux-1.10.3-1.el7.centos.noarch.rpm is not installed
Importing GPG key 0x2C52609D:
 Userid     : "Docker Release Tool (releasedocker) <docker@docker.com>"
 Fingerprint: 5811 8e89 f3a9 1289 7c07 0adb f762 2157 2c52 609d
 From       : https://yum.dockerproject.org/gpg
setsebool:  SELinux is disabled.

If you would like to use Docker as a non-root user, you should now consider
adding your user to the "docker" group with something like:

  sudo usermod -aG docker your-user

Remember that you will have to log out and back in for this to take effect!

[root@localhost ~]# sudo service docker start
Redirecting to /bin/systemctl start  docker.service

[root@localhost ~]# sudo docker run hello-world
Unable to find image 'hello-world:latest' locally
latest: Pulling from library/hello-world
03f4658f8b78: Pull complete 
a3ed95caeb02: Pull complete 
Digest: sha256:8be990ef2aeb16dbcb9271ddfe2610fa6658d13f6dfb8bc72074cc1ca36966a7
Status: Downloaded newer image for hello-world:latest

Hello from Docker.
This message shows that your installation appears to be working correctly.

To generate this message, Docker took the following steps:
 1. The Docker client contacted the Docker daemon.
 2. The Docker daemon pulled the "hello-world" image from the Docker Hub.
 3. The Docker daemon created a new container from that image which runs the
    executable that produces the output you are currently reading.
 4. The Docker daemon streamed that output to the Docker client, which sent it
    to your terminal.

To try something more ambitious, you can run an Ubuntu container with:
 $ docker run -it ubuntu bash

Share images, automate workflows, and more with a free Docker Hub account:
 https://hub.docker.com

For more examples and ideas, visit:
 https://docs.docker.com/userguide/

[root@localhost ~]# systemctl enable docker
Created symlink from /etc/systemd/system/multi-user.target.wants/docker.service to /usr/lib/systemd/system/docker.service.

usermod -aG docker your_username