Cannot kill or detach a docker container using Ctrl-C or Ctrl-\

[vmalloc]

Hi,

Running docker 0.6.7 on Ubuntu 13.04.

I built a container whose CMD executes a uwsgi process (also tried with other executables). I run without detaching, and sigproxy is True.

Hitting Ctrl-C seems to have no effect over the running container and the only way to leave it or kill it is with docker kill and docker stop...

Is this a known issue?

[lhazlewood]

Starting with docker 0.6.5, you can add -t to the docker run command, which will attach a pseudo-TTY. Then you can type Control-C to detach from the container without terminating it.

If you use -t and -i then Control-C will terminate the container. When using -i with -t then you have to use Control-P Control-Q to detach without terminating.

Test 1:

$ ID=$(sudo docker run -t -d ubuntu /usr/bin/top -b)
$ sudo docker attach $ID
Control-C
$ sudo docker ps

The container is still listed.

Test 2:

$ ID=$(sudo docker run -t -i -d ubuntu /usr/bin/top -b)
$ sudo docker attach $ID
Control-C
$ sudo docker ps

the container is not there (it has been terminated). If you type Control-P Control-Q instead of Control-C in the 2nd example, the container would still be running.

A pull request to fix the docs for the Hello World daemon sample is here:

#2845

I'm unaware of where you saw the recommendation to Control-C outside of this example. If you saw this reference somewhere else, can you please submit a new pull request to fix the docs you referenced?

You might also find this mailing list thread helpful.

[alexlarsson]

@lhazlewood Well, -t -d lets you kill the container with ctrl-c in the docker attach, however the problem is:

$ ID=$(docker run -d ubuntu bash -c "while true; do echo foo; sleep 5; done")
$ docker attach $ID

In this case ctrl-C does nothing. I expected it to kill the "docker attach" process (not the container).

[alexlarsson]

If the daemon was not started with -t, i think docker attach should default to -sig-proxy=false

[vmalloc]

From what I can gather you need both -t and -i for Ctrl-C to work as expected...

[alexlarsson]

@vmalloc That depends on what you expect. I expect to be able to detach from "docker attach" with ctrl-c, not kill the daemon. That is not currently possible without manually specifying -sig-proxy=false. If you accidentally do this the only way out is to kill the docker attach process from another terminal.

[alexlarsson]

Ah, sorry I was a bit confused above. If you run "docker run -d -t" and the docker attach, then ctrl-c does detach, not kill the daemon. The problem is that if you forgot the -t, and then ever use docker attach you end up with something you can't detach without killing it from a different terminal.

[lhazlewood]

@alexlarsson Yes, the two test cases I show above show what happens w/ and w/o -i.

[dmp1ce]

Yes, I am experiencing the same issue. An easy way to reproduce is docker run busybox sleep 60 and then CTRL-C all you want. The command will not terminate or detach until the 60 seconds is up. I would expect a CTRL-C to send a SIGTERM to the sleep command, which should stop the docker instance.

[lhazlewood]

Also see #2855

[cpuguy83]

To have ctrl+c stop the container you must use -it
To detach from the container you should use ctrl+pq

Closing.

[lhazlewood]

Why was this closed? Can you please explain the reason?

I asked because it is obvious that the majority of the community does not want the current default behavior.

Also note that ctrl+pq does not work on Mac OS X running Ubuntu in VirtualBox.

[cpuguy83]

@lhazlewood Because the issue wasn't about ctrl+pq it was about getting out of attach with ctrl-c, which is not supported since "attach" is litterally attaching you to the running process and should be expected behavior.
If you just want the stdout+stderr streams you should use docker logs not attach.
I see this as a training issue and not a Docker issue.

If we want to discuss changing ctrl-pq, and I know I've seen other issues around it that's fine.
I'm not sure that we can change it at this point.
We talked about introducing a configurable command for it but was implemented server side and just wasn't ideal and implementing it client-side is difficult.

And I write all this in the friendliest of tone, I'm terse by nature, sorry about that.

[rolkar]

I am VERY confused by all this.

The default behaviour when being in a shell prompt is that ^C kills the running foreground process. And if no such process exists, it just do nothing, except maybe show a new prompt. ^D on the other hand do exit the shell, without stopping the machine. This is what I expect, because this is what everyone else do.

So, why do Docker do it differently? And why do I read this strange discussion? Am I missing something?

[cpuguy83]

@rolkar Because there are two foreground processes in this case.
The process you're attached to in the container and the docker client.

I personally think this should behave in much the same way as SSH, though with a different escape sequence.
FYI SSH's escape sequence is <enter>~.