Difference between Running and Starting a Docker container

Question

In practice to start a container I do   docker run a8asd8f9asdf0   If thats the case  what does   docker start   do   In the manual it says     Start one or more stopped containers

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run - Create a container using image and Start the same   Create  amp  Start   start - Start the container s  in docker list which was in stopped state

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Explanation with an example   Consider you have a game  iso  image in your computer     When you run  mount your image as a virtual drive   a virtual drive is created with all the game contents in the virtual drive and the game installation file is automatically launched   Running your docker image - creating a container and then starting it    But when you stop  similar to docker stop  it  the virtual drive still exists but stopping all the processes   As the container exists till it is not deleted   And when you do start  similar to docker start   from the virtual drive the games files start its execution   starting the existing container   In this example - The game image is your Docker image and virtual drive is your container

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run command creates a container from the image and then starts the root process on this container  Running it with run --rm flag would save you the trouble of removing the useless dead container afterward and would allow you to ignore the existence of docker start and docker remove altogether     run command does a few different things   docker run --name dname image name bash -c  whoami     Creates a Container from the image  At this point container would have an id  might have a name if one is given  will show up in docker ps Starts executes the root process of the container  In the code above that would execute bash -c  whoami   If one runs docker run --name dname image name without a command to execute container would go into stopped state immediately   Once the root process is finished  the container is stopped  At this point  it is pretty much useless  One can not execute anything anymore or resurrect the container  There are basically 2 ways out of stopped state  remove the container or create a checkpoint  i e  an image  out of stopped container to run something else  One has to run docker remove before launching container under the same name    How to remove container once it is stopped automatically  Add an --rm flag to run command    docker run --rm --name dname image name bash -c  whoami    How to execute multiple commands in a single container  By preventing that root process from dying  This can be done by running some useless command at start with --detached flag and then using  execute  to run actual commands   docker run --rm -d --name dname image name tail -f  dev null docker exec dname bash -c  whoami  docker exec dname bash -c  echo  Nnice     Why do we need docker stop then  To stop this lingering container that we launched in the previous snippet with the endless command tail -f  dev null

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This is a very important question and the answer is very simple  but fundamental    Run  create a new container of an image  and execute the container  You can create N clones of the same image  The command is  docker run IMAGE ID and not docker run CONTAINER ID      Start  Launch a container previously stopped  For example  if you had stopped a database with the command docker stop CONTAINER ID  you can relaunch the same container with the command docker start CONTAINER ID  and the data and settings will be the same

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daniele3004 s answer is already pretty good   Just a quick and dirty formula for people like me who mixes up run and start from time to time   docker run         docker pull         docker start

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run runs an image start starts a container   The docker run doc does mention   The docker run command first creates a writeable container layer over the specified image  and then starts it using the specified command  That is  docker run is equivalent to the API  containers create then  containers  id  start   You do not run an existing container  you docker exec to it  since docker 1 3   You can restart an exited container

[docker] Difference between Running and Starting a Docker container

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