[docker] Correct way to detach from a container without stopping it

In Docker 1.1.2 (latest), what's the correct way to detach from a container without stopping it?

So for example, if I try:

• docker run -i -t foo /bin/bash or
• docker attach foo (for already running container)

both of which get me to a terminal in the container, how do I exit the container's terminal without stopping it?

exit and CTR+C both stop the container.

Old post but just exit then start it again... the issue is if you are on a windows machine Ctrl p or Ctrl P are tied to print... exiting the starting the container should not hurt anything

Try CTRL+P,CTRL+Q to turn interactive mode to daemon.

If this does not work and you attached through docker attach, you can detach by killing the docker attach process.

Better way is to use sig-proxy parameter to avoid passing the CTRL+C to your container :

docker attach --sig-proxy=false [container-name]

Same option is available for docker run command.

Type Ctrl+p then Ctrl+q. It will help you to turn interactive mode to daemon mode.

See https://docs.docker.com/v1.7/articles/basics/#running-an-interactive-shell.

# To detach the tty without exiting the shell,
# use the escape sequence Ctrl-p + Ctrl-q
# note: This will continue to exist in a stopped state once exited (see "docker ps -a")

If you just want see the output of the process running from within the container, you can do a simple docker container logs -f <container id>.

The -f flag makes it so that the output of the container is followed and updated in real-time. Very useful for debugging or monitoring.

If you do "docker attach "container id" you get into the container. To exit from the container without stopping the container you need to enter Ctrl+P+Q

I dug into this and all the answers above are partially right. It all depends on how the container is launched. It comes down to the following when the container was launched:

• was a TTY allocated (-t)
• was stdin left open (-i)

^P^Q does work, BUT only when -t and -i is used to launch the container:

[berto@g6]$ docker run -ti -d --name test python:3.6 /bin/bash -c 'while [ 1 ]; do sleep 30; done;'
b26e39632351192a9a1a00ea0c2f3e10729b6d3e22f8e0676d6519e15c08b518

[berto@g6]$ docker attach test
# here I typed ^P^Q
read escape sequence

# i'm back to my prompt
[berto@g6]$ docker kill test; docker rm -v test
test
test

ctrl+c does work, BUT only when -t (without -i) is used to launch the container:

[berto@g6]$ docker run -t -d --name test python:3.6 /bin/bash -c 'while [ 1 ]; do sleep 30; done;'
018a228c96d6bf2e73cccaefcf656b02753905b9a859f32e60bdf343bcbe834d

[berto@g6]$ docker attach test
^C

[berto@g6]$    

The third way to detach

There is a way to detach without killing the container though; you need another shell. In summary, running this in another shell detached and left the container running pkill -9 -f 'docker.*attach':

[berto@g6]$ docker run -d --name test python:3.6 /bin/bash -c 'while [ 1 ]; do sleep 30; done;'
b26e39632351192a9a1a00ea0c2f3e10729b6d3e22f8e0676d6519e15c08b518

[berto@g6]$ docker attach test
# here I typed ^P^Q and doesn't work
^P
# ctrl+c doesn't work either
^C
# can't background either
^Z

# go to another shell and run the `pkill` command above

# i'm back to my prompt
[berto@g6]$

Why? Because you're killing the process that connected you to the container, not the container itself.

I consider Ashwin's answer to be the most correct, my old answer is below.

docker run -dti foo bash

You can then enter the container and run bash with

docker exec -ti ID_of_foo bash

No need to install sshd :)

In Docker container atleast one process must be run, then only the container will be running the docker image(ubuntu,httd..etc, whatever it is) at background without exiting

For example in ubuntu docker image ,

To create a new container with detach mode (running background atleast on process),

docker run -d -i -t f63181f19b2f /bin/bash

it will create a new contain for this image(ubuntu) id f63181f19b2f . The container will run in the detached mode (running in background) at that time a small process tty bash shell will be running at background. so, container will keep on running untill the bash shell process will killed.

To attach to the running background container,use

docker attach  b1a0873a8647

if you want to detach from container without exiting(without killing the bash shell), By default , you can use ctrl-p,q. it will come out of container without exiting from the container(running background. that means without killing the bash shell).

You can pass the custom command during attach time to container,

docker attach --detach-keys="ctrl-s" b1a0873a8647

this time ctrl-p,q escape sequence won't work. instead, ctrl-s will work for exiting from container. you can pass any key eg, (ctrl-*)

The default way to detach from an interactive container is Ctrl+P Ctrl+Q, but you can override it when running a new container or attaching to existing container using the --detach-keys flag.

You can simply kill docker cli process by sending SEGKILL. If you started the container with

docker run -it some/container

You can get it's pid

ps -aux | grep docker

user   1234  0.3  0.6 1357948 54684 pts/2   Sl+  15:09   0:00 docker run -it some/container

let's say it's 1234, you can "detach" it with

kill -9 1234

It's somewhat of a hack but it works!

You can use the --detach-keys option when you run docker attach to override the default CTRL+P, CTRL + Q sequence (that doesn't always work).

For example, when you run docker attach --detach-keys="ctrl-a" test and you press CTRL+A you will exit the container, without killing it.

Other examples:

• docker attach --detach-keys="ctrl-a,x" test - press CTRL+A and then X to exit
• docker attach --detach-keys="a,b,c" test - press A, then B, then C to exit

Extract from the official documentation:

If you want, you can configure an override the Docker key sequence for detach. This is useful if the Docker default sequence conflicts with key sequence you use for other applications. There are two ways to define your own detach key sequence, as a per-container override or as a configuration property on your entire configuration.

To override the sequence for an individual container, use the --detach-keys="<sequence>" flag with the docker attach command. The format of the <sequence> is either a letter [a-Z], or the ctrl- combined with any of the following:

• a-z (a single lowercase alpha character )
• @ (at sign)
• [ (left bracket)
• \ (two backward slashes)
• _ (underscore)
• ^ (caret)

These a, ctrl-a, X, or ctrl-\\ values are all examples of valid key sequences. To configure a different configuration default key sequence for all containers, see Configuration file section.

Note: This works since docker version 1.10+ (at the time of this answer, the current version is 18.03)