Install docker on CentOS 6.x

STEP1:
yum install epel-release

STEP2:
Running this command will update the repo to use HTTP rather than HTTPS:
sudo sed -i "s/mirrorlist=https/mirrorlist=http/" /etc/yum.repos.d/epel.repo

STEP 3:
You should then be able to update with this command:
yum -y update

Step 4:
Yum install docker-io

Details and reasons of the above steps:

• https://docs.docker.com/installation/centos/
• https://fedoraproject.org/wiki/EPEL#How_can_I_use_these_extra_packages.3F
• https://community.hpcloud.com/article/centos-63-instance-giving-cannot-retrieve-metalink-repository-epel-error