How to Retain Docker Alpine Container After "Exit" Is Used

How to retain docker alpine container after exit is used?

Pull an image

docker image pull alpine

See that image is there

docker image ls   OR  just docker images

see what is inside the alpine

docker run alpine ls -al

Now your question is how to stay with the shell

docker container run -it alpine /bin/sh

You are inside shell script command line. Some distribution may have bash shell.

 docker exec -it 5f4 sh
 / # (<-- you can run linux command here!)

At this point, you can use command line of alpine and do

ls -al

type exit to come out-
You can run it in detached mode and it will keep running.

With exec command we can login again

docker container run -it -d alpine /bin/sh

verify that it is UP and copy the FIRST 2 -3 digits of the container ID

docker container ls

login with exec command

docker exec -it <CONTAINER ID or just 2-3 digits> sh

You will need to STOP otherwise it will keep running.

docker stop <CONTAINER ID>

Docker container will automatically stop after docker run -d

The centos dockerfile has a default command bash.

That means, when run in background (-d), the shell exits immediately.

Update 2017

More recent versions of docker authorize to run a container both in detached mode and in foreground mode (-t, -i or -it)

In that case, you don't need any additional command and this is enough:

docker run -t -d centos

The bash will wait in the background.

That was initially reported in kalyani-chaudhari's answer and detailed in jersey bean's answer.

vonc@voncvb:~$ d ps -a
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES
4a50fd9e9189        centos              "/bin/bash"         8 seconds ago       Up 2 seconds                            wonderful_wright

Note that for alpine, Marinos An reports in the comments:

docker run -t -d alpine/git does not keep the process up.

Had to do: docker run --entrypoint "/bin/sh" -it alpine/git

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Original answer (2015)

As mentioned in this article:

Instead of running with docker run -i -t image your-command, using -d is recommended because you can run your container with just one command and you don’t need to detach terminal of container by hitting Ctrl + P + Q.

However, there is a problem with -d option. Your container immediately stops unless the commands keep running in foreground.

Docker requires your command to keep running in the foreground. Otherwise, it thinks that your applications stops and shutdown the container.

The problem is that some application does not run in the foreground. How can we make it easier?

In this situation, you can add tail -f /dev/null to your command.

By doing this, even if your main command runs in the background, your container doesn’t stop because tail is keep running in the foreground.

So this would work:

docker run -d centos tail -f /dev/null

Or in Dockerfile:

ENTRYPOINT ["tail"]
CMD ["-f","/dev/null"]

A docker ps would show the centos container still running.

From there, you can attach to it or detach from it (or docker exec some commands).

How to keep Docker container running after starting services?

This is not really how you should design your Docker containers.

When designing a Docker container, you're supposed to build it such that there is only one process running (i.e. you should have one container for Nginx, and one for supervisord or the app it's running); additionally, that process should run in the foreground.

The container will "exit" when the process itself exits (in your case, that process is your bash script).

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However, if you really need (or want) to run multiple service in your Docker container, consider starting from "Docker Base Image", which uses runit as a pseudo-init process (runit will stay online while Nginx and Supervisor run), which will stay in the foreground while your other processes do their thing.

They have substantial docs, so you should be able to achieve what you're trying to do reasonably easily.

How to continue a Docker container which has exited

You can restart an existing container after it exited and your changes are still there.

docker start  `docker ps -q -l` # restart it in the background
docker attach `docker ps -q -l` # reattach the terminal & stdin

Why docker container exits immediately

A docker container exits when its main process finishes.

In this case it will exit when your start-all.sh script ends. I don't know enough about hadoop to tell you how to do it in this case, but you need to either leave something running in the foreground or use a process manager such as runit or supervisord to run the processes.

I think you must be mistaken about it working if you don't specify -d; it should have exactly the same effect. I suspect you launched it with a slightly different command or using -it which will change things.

A simple solution may be to add something like:

while true; do sleep 1000; done


to the end of the script. I don't like this however, as the script should really be monitoring the processes it kicked off.

(I should say I stole that code from https://github.com/sequenceiq/hadoop-docker/blob/master/bootstrap.sh)

How to make a docker container exit with a specific error-code with docker-compose?

Look at your error messages more closely:

ERROR: for docker-compose_dummy_1  Cannot start service dummy: OCI
runtime create failed: container_linux.go:345: starting container
process caused "exec: \"exit\": executable file not found in $PATH":
unknown

When you specify an entrypoint like ["exit", "42"], it's not executed in a shell. Docker is looking for a command in your $PATH named exit, and of course no such command exists.

You need to run your commands in a shell, because exit is a shell command:

    entrypoint: ["/bin/sh", "-c", "exit 42"]

Starting a shell in the Docker Alpine container

ole@T:~$ docker run -it --rm alpine /bin/ash
(inside container) / # 

Options used above:

• /bin/ash is Ash (Almquist Shell) provided by BusyBox
• --rm Automatically remove the container when it exits (docker run --help)
• -i Interactive mode (Keep STDIN open even if not attached)
• -t Allocate a pseudo-TTY

Docker - Container is not running

Container 79b3fa70b51d seems to only do an echo.

That means it starts, echo and then exits immediately.

The next docker exec command wouldn't find it running in order to attach itself to that container and execute any command: it is too late. The container has already exited.

The docker exec command runs a new command in a running container.

The command started using docker exec will only run while the container's primary process (PID 1) is running

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