What is the difference between Docker Service and Docker Container?

Question

When do we use a docker service create command and when do we use a docker run command?

Answer 1

In short: Docker service is used mostly when you configured the master node with Docker swarm so that docker containers will run in a distributed environment and it can be easily managed.

Docker run: 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

source: https://docs.docker.com/engine/reference/commandline/run/#parent-command

Docker service: Docker service will be the image for a microservice within the context of some larger application. Examples of services might include an HTTP server, a database, or any other type of executable program that you wish to run in a distributed environment.

When you create a service, you specify which container image to use and which commands to execute inside running containers. You also define options for the service including:

• the port where the swarm will make the service available outside the swarm
• an overlay network for the service to connect to other services in the swarm
• CPU and memory limits and reservations
• a rolling update policy
• the number of replicas of the image to run in the swarm

source: https://docs.docker.com/engine/swarm/how-swarm-mode-works/services/#services-tasks-and-containers

Answer 2

• docker run is used to create a standalone container
• docker service create is used to create instances (called tasks) of that service running in a cluster (called swarm) of computers (called nodes). Those tasks are containers of cource, but not standalone containers. In a sense a service acts as a template when instantiating tasks.

For example

docker service create --name MY_SERVICE_NAME --replicas 3 IMAGE:TAG 

creates 3 tasks of the MY_SERVICE_NAME service, which is based on the IMAGE:TAG image.

More information can be found here