#Add your user without needing sudo
sudo usermod -aG docker $USER
#List all docker images and tags on a machine
docker images --format {{.Repository}} > name_docker_images.tmp && docker images --format {{.Tag}} > name_docker_tags.tmp
sed -i 's/$/:/' name_docker_images.tmp
paste name_docker_images.tmp name_docker_tags.tmp > imagelist.txt
rm name_docker_images.tmp name_docker_tags.tmp
sed -i 's/\t//g' imagelist.txt
cat imagelist.txt
#once you verify delete imagelist file
rm imagelist.txt
https://www.katacoda.com/courses/docker
Make sure you have a VM
Use this guide to install docker on CentOS7