A Docker image contains the code used to create a Docker container, such as creating a Nginx web server, or a mySQL server, or a home grown app, and the list goes on. In this way, an image is like a template used to create a container. An image is kind of like a virtual machine, but much more light weight, using significantly less storage a memory (containers are usually megabytes in size).
The docker ps command will return the running containers.
Which will return something like this. If the container was created but not yet started, the status of the container will be "created".
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES d937372c09ab9 b939aa938add9913 "/docker-entrypoin..." 6 minutes ago Created my-container
After using the docker start command to start the container, the status of the container should either be "up xxx" or "exited". If the container is up, the socket (ip address:port) being used by the container will be displayed. If the status is "exited", use the docker logs command to determine why the container failed to start.
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES d937372c09ab9 b939aa938add9913 "/docker-entrypoin..." 6 minutes ago Up 30 seconds 0.0.0.0:12345->12345/tcp
The docker ps -a command returns both running and inactive containers.
docker ps -a
If the status of the container is "Exited (1)", attempt to start the container using the docker start command. If the container still has a status of Exited, check the docker logs.