Once you have deployed a service to a swarm, you are ready to use the Docker CLI to scale the number of containers in the service. Containers running in a service are called “tasks.”
If you haven’t already, open a terminal and ssh into the machine where you run your manager node. For example, the tutorial uses a machine named
Run the following command to change the desired state of the service running in the swarm:
$ docker service scale <SERVICE-ID>=<NUMBER-OF-TASKS>
$ docker service scale helloworld=5 helloworld scaled to 5
docker service ps <SERVICE-ID> to see the updated task list:
$ docker service ps helloworld NAME IMAGE NODE DESIRED STATE CURRENT STATE helloworld.1.8p1vev3fq5zm0mi8g0as41w35 alpine worker2 Running Running 7 minutes helloworld.2.c7a7tcdq5s0uk3qr88mf8xco6 alpine worker1 Running Running 24 seconds helloworld.3.6crl09vdcalvtfehfh69ogfb1 alpine worker1 Running Running 24 seconds helloworld.4.auky6trawmdlcne8ad8phb0f1 alpine manager1 Running Running 24 seconds helloworld.5.ba19kca06l18zujfwxyc5lkyn alpine worker2 Running Running 24 seconds
You can see that swarm has created 4 new tasks to scale to a total of 5 running instances of Alpine Linux. The tasks are distributed between the three nodes of the swarm. One is running on
docker ps to see the containers running on the node where you’re connected. The following example shows the tasks running on
$ docker ps CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES 528d68040f95 alpine:latest "ping docker.com" About a minute ago Up About a minute helloworld.4.auky6trawmdlcne8ad8phb0f1
If you want to see the containers running on other nodes, ssh into those nodes and run the
docker ps command.
At this point in the tutorial, you’re finished with the
helloworld service. The next step shows how to delete the service.
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