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Accepted
Timur Fayzrakhmanov
Asked: 2014-08-02 08:19:07 +0800 CST

How to get bash or ssh into a running container in background mode?

  • 772

I want to ssh or bash into a running docker container. Please, see example:

$ sudo docker run -d webserver
webserver is clean image from ubuntu:14.04
$ sudo docker ps
CONTAINER ID  IMAGE            COMMAND    CREATED STATUS  PORTS          NAMES
665b4a1e17b6  webserver:latest /bin/bash  ...     ...     22/tcp, 80/tcp loving_heisenberg

Now I want to get something like this (go into the running container):

$ sudo docker run -t -i webserver (or maybe 665b4a1e17b6 instead)
$ root@665b4a1e17b6:/#

However when I run the line above I get new CONTAINER ID:

$ root@42f1e37bd0e5:/#

I used Vagrant and I'd like to get a similar behaviour as vagrant ssh.

bash

15 Answers

  1. Best Answer

    The answer is Docker's attach command. So for my example above, the solution will be:

    $ sudo docker attach 665b4a1e17b6 #by ID
or
$ sudo docker attach loving_heisenberg #by Name
$ root@665b4a1e17b6:/#

    For Docker version 1.3 or later: Thanks to user WiR3D who suggested another way to get a container's shell. If we use attach we can use only one instance of the shell. So if we want open a new terminal with a new instance of a container's shell, we just need to run the following:

    $ sudo docker exec -i -t 665b4a1e17b6 /bin/bash #by ID

    or

    $ sudo docker exec -i -t loving_heisenberg /bin/bash #by Name
$ root@665b4a1e17b6:/#
    • 1346

  2. From Docker 1.3 onwards:

    docker exec -it <containerIdOrName> bash

    Basically, if the Docker container was started using the /bin/bash command you can access it using attach. If not, then you need to execute the command to create a Bash instance inside the container using exec.

    Also to exit Bash without leaving Bash running in a rogue process:

    exit

    Yep, it is that simple.

    • 707

  3. Although the author of the question specifically said they are interested in a running container, it's also worth noting that if the container is not running, but you'd like to run it to poke around you can run:

    docker run -i -t --entrypoint /bin/bash <imageID>

    • 129

  4. Try this:

    sudo docker run -i -t webserver /bin/bash

    Source: https://docs.docker.com/engine/reference/commandline/run/

    • 29

  5. Based on @Timur's answer I've created the following handy script

    Setup

    Put docker-ssh file in your $PATH with the following contents

    #!/bin/bash -xe

# docker container id or name might be given as a parameter
CONTAINER=$1

if [[ "$CONTAINER" == "" ]]; then
  # if no id given simply just connect to the first running container
  CONTAINER=$(docker ps | grep -Eo "^[0-9a-z]{8,}\b")
fi

# start an interactive bash inside the container
# note some containers don't have bash, then try: ash (alpine), or simply sh
# the -l at the end stands for login shell that reads profile files (read man)
docker exec -i -t $CONTAINER bash -l

    Note: Some container do not contain bash, but ash, sh etc. In these cases bash shall be replaced in the above script.

    Usage

    If you have only one running instance, simply run

    $> docker-ssh

    Otherwise, provide it with a docker id parameter that you get from docker ps (first col)

    $> docker-ssh 50m3r4nd0m1d
    • 20

  6. If your container doesn't have bash installed you could try sh:

    docker exec -it CONTAINER /bin/sh

    Or look for shells in /bin first:

    docker export CONTAINER|tar -t|egrep ^bin/
    • 18

  7. I've created a containerized SSH server that provides SSH capabilities to any running container. You don't need to change your container. The only requirement is that the container has bash.

    If you have a container with name 'web-server1'. The following docker run command would start a second container that would provide SSH for the first container.

    docker run -ti --name sshd-web-server1 -e CONTAINER=web-server1 -p 2222:22 \
-v /var/run/docker.sock:/var/run/docker.sock -v $(which docker):/usr/bin/docker \
jeroenpeeters/docker-ssh

    For more pointers, checkout https://github.com/jeroenpeeters/docker-ssh

    • 9

  8. @jpetazzo has an awesome post about this subject. The short answer would be to use nsenter:

    PID=$(docker inspect --format {{.State.Pid}} <container_name_or_ID>)
nsenter --target $PID --mount --uts --ipc --net --pid

    P.S.: Don't forget to check the discussion in the comments of the post...

    Cheers

    • 6

  9. You can also give the Docker container a routeable IP address with Pipework, and after that SSH into the machine with that new IP address.

    This will be more "traditional" (ssh), instead of using an application-specific command like docker attach, and will eventually make it more 'portable' across systems and versions.

    • 4

  10. Sometimes it will be handy to be able to ssh into a Docker container, especially during development. The following Docker image allows to ssh into a container using a private key:

    UbuntuWithSSH-Docker

    The gist of the Dockerfile is https://gist.github.com/devbkhadka/98792f7bca57f9778793b2db758b3d07.

    • 3