Q:

What is the meaning of docker ps -a

What is the meaning of "-a" from docker ps -a
docker ps is lists all running containers in docker engine.
When we run docker ps -a it will list the container that had stop as well. 
What is meaning of "-a" ?

A:

-a is short form for --all.
It shows all the containers both stopped and running.
Normal docker ps shows only the running containers.
When you provide the option -a, it shows all the containers.
Please check this for further details: :)
Docker ps options

