CONTINUAL INTEGRATION

Update on 11/20/20: We recommend you see How Do You Install the docker.service File on RHEL 8.x? instead of the directions below. (Many times this command will work: sudo yum -y install docker )

Update on 9/10/19: These directions below work to install Docker version 17.05.0-ce on RHEL 8.x.

These "directions" to install Docker on RedHat Enterprise Linux include a script and how to run it.  The script was designed to install Docker 1.12 on an AWS instance of RHEL 7.x.  This script requires that your AWS RHEL server is in a security group that has access to the Internet.  The script takes approximately 10 minutes to run.  But bandwidth and resources on your instance may vary.  The benefit of these directions is that they will work when you may not run the "yum-config-manager" command.  The script below uses CentOS packages which are not ideal for RHEL.  If you can run the "yum-config-manager" command, see these alternative directions.  (If you want a variety of different directions for installing Docker, please see this posting.)

Step #1  Log in and become root.
Step #2  Run these commands:

cd /tmp/
touch installer.sh
chmod u+x installer.sh
vi installer.sh  #then paste everything below up to and including the 'echo "docker run -it centos /bin/bash"' line

#!/bin/bash
#Written by continualintegration.com
yum -y update
echo '
[dockerrepo]
name=Docker Repository
baseurl=https://yum.dockerproject.org/repo/main/centos/7/
enabled=1
gpgcheck=1
gpgkey=https://yum.dockerproject.org/gpg' > /etc/yum.repos.d/docker.repo
yum -y install docker-engine
groupadd docker
usermod -aG docker ec2-user
service docker start
echo "run 'docker run hello-world' to test it out"
echo "Afterward, you can run "
echo "docker run -it ubuntu bash"
echo "or you can run"
echo "docker run -it centos /bin/bash"
echo "Log out and log back in"

Step #4  Save the file.
Step #5  Run the script with a command like this: ./installer.sh
Step #6  Test it with a command like this:  docker run hello-world
(You may need to log out and log back in.  Instead of the "chmod" command above, you could run it with "sudo bash".)
Step #7 Enter a docker container with a command like this:  docker run -it centos /bin/bash

(If you want to install Docker on a RHEL VM running in GCP, see this posting.)

We recommend you see How Do You Install the docker.service File on RHEL 8.x? instead of the directions above.

Updated 12/26/18
Problem scenario
You want to install Docker.  You can make changes to the Ubuntu Linux repositories so you can use apt-get to install it.  How do you install Docker on an AWS EC-2 instance?

Solution
There is an alternative set of directions if you click on this link here (if you would prefer not to configure the apt-get repositories).  These directions below to install Docker on Ubuntu Linux include a script and how to run it (but the script below will make a change to the repositories that the Linux server uses).  The script was designed to install Docker 1.12 on an AWS instance of Ubuntu 14.04, 16.04 or 18.04.  These directions assume that the user that will run Docker commands is named "ubuntu"; the "usermod" stanza associates this user with the group named "docker".  Please note that these directions do work for installing Docker on an Azure instance of Ubuntu too!  For AWS this script requires that your Ubuntu Linux server is in a security group that has access to the Internet.  The script takes approximately three minutes to run in AWS.  It may or may not take longer in Azure.  Bandwidth and resources on your instance may vary.  (If you want a variety of different Docker installation directions, see this posting.)

Step #1  Log in and become root.
Step #2  Run these commands:

cd /tmp/
touch installer.sh
chmod u+x installer.sh   # this is unnecessary if you prefer to run the script with the "sudo bash installer.sh" command
vi installer.sh

Step #3  Enter this text into the file from "#!/bin/bash" (the first line) to the line '"echo "docker run -it ubuntu bash""' (the last line):

#!/bin/bash
apt-get update
apt-get install -y apt-transport-https ca-certificates
sudo apt-key adv --keyserver hkp://p80.pool.sks-keyservers.net:80 --recv-keys 58118E89F3A912897C070ADBF76221572C52609D
echo 'deb https://apt.dockerproject.org/repo ubuntu-trusty main' > /etc/apt/sources.list.d/docker.list
echo 'deb http://cz.archive.ubuntu.com/ubuntu trusty main' >> /etc/apt/sources.list.d/docker.list
apt-get update
apt-cache policy docker-engine
apt-get --assume-yes install linux-image-extra-$(uname -r) linux-image-extra-virtual
apt-get --assume-yes install docker-engine
sudo service docker start
sudo groupadd docker
sudo usermod -aG docker ubuntu
docker run hello-world
echo "Try running this command below to enter a Docker container:"
echo "docker run -it ubuntu bash"

Step #4  Save the changes. 
Step #5  Run the script (./installer.sh).  (An alternative way is to use "sudo bash installer.sh".)
Step #6  If you ran the above script when you were logged in with the "ubuntu" username, you will need to log out and log back in.  Otherwise start a new terminal session with the "ubuntu" user. Then run this command with no quotes to enter the Docker container:  "docker run -it ubuntu bash"