CODEWITHSUNDEEP
dockerdocker-containerdocker-run
Jim
Jim

Reputation: 4405

Is there a min condition for a container to continue running?

Why does the container exit when the entry point specifies to run a command in the background? E.g. if I run docker run -d ubuntu bash -c "sleep 12000&" the container exits. If I run docker run -d ubuntu bash -c "sleep 12000" the container continues to run.
Isn't a process in the background sufficient to keep the container running?
Why does the sleep running in the background or foreground affect this?

Upvotes: 0

Views: 164

Answers (3)

David Maze
David Maze

Reputation: 158898

A simple criterion might be the following: if you run a command locally and it immediately returns and gives you a shell prompt back, then if you run that command as the main process in a container, the container will immediately exit.

Usual best practice is to have a container run some process, like a network server, as a foreground process, and when that server exits the container is done. In the ideal case the container is totally autonomous: once you docker run it, it does its thing without any user intervention. (In this model a plain Ubuntu container, with no software installed, that only sleeps, isn’t that interesting.)

Upvotes: 1

Siyu
Siyu

Reputation: 12089

As suggested by grapes, the condition is that PID 1 is running.

The container is designed to be short-lived and specialized in one task (microservice) which runs as PID 1 in the foreground. Background is of course useful for things like ssh, but the container has to have a main job.

Most service can be run both on foreground or background (deamonized)

PS. if you have to keep a container alive, use tail -f /dev/null as CMD

Upvotes: 1

grapes
grapes

Reputation: 8636

According to Docker's mans, container is supposed to be running while

the container’s primary process (PID 1) is running

In your case primary process bash and container "runs" until this process exits.

Upvotes: 1

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