Installing Docker

All commands as root on CentOs7:

cd /etc/yum.repos.d
vim docker.repo

[dockerrepo]
name=Docker Repository
baseurl=https://yum.dockerproject.com/repos/main/centos/7/
enabled=true
gpgcheck=1
gpgkey=https://yum.dockerproject.org/gpg

yum install docker-engin

systemctl enable docker
systemctl start docker

usermod -a -G docker <username>
cat /etc/group | grep docker #should use the <username> as the group for the docker program

Docker Commands

List images:

docker images

List running docker processes:

docker ps

List all processes that were ever run:

docker ps -a

List only the container IDs:

docker ps -a -q

Running processes:

docker run <image>
docker run -d <image> = run in disconnected / daemon mode
docker run --name="Some Name" = name the running instance
docker start <name> = will restart a closed / exited instance of the image
docker exec -it <name> <command> = run a command within a running container without changing the state of the running container
docker stop <name> = stop a running container by using the name

Cleaning up Docker:

docker rm containerid = removes an instance of the container that was run
docker rm `docker ps -a -q` = remove all stopped containers
docker rmi image-name = removes the docker image and its dependencies

Redirect port:

docker run -P = will redirect the container's port to a random port on the host machine's user port (port no 32,000+)
docker run -p 8080:80 = will redirect the container's port 80 to a port 8080 on the host machine's user port 
docker port <container-name> = will list the port mapping information

Adding volume:

using the "-v" option mounts the local file system. eg to mount for an nginx on centos
-v /home/user/www:/usr/share/nginx/html

Building a Docker file:

docker login --username=<username>
Enter password

docker push username/repo