Docker: attach to a specific bash

Question

Lets say I have a container running and I do

docker exec -ti container-id /bin/bash

Then I detach from this container and want to attach again

If I do this

docker attach container-id

I wont go back to that bash that I created. Instead I will go to the main process.

How can I attach to that bash again ?

Answer 1

I have one container and I have started it using, and checked the pid of /bin/bash

[root@ip-10-0-1-153 centos]# docker exec -ti 78c2e4a46b58 /bin/bash
root@78c2e4a46b58:/# ps -ef
UID        PID  PPID  C STIME TTY          TIME CMD
root         1     0  0 03:24 ?        00:00:00 bash
root        10     0  0 03:24 ?        00:00:00 /bin/bash
root        20    10  0 03:24 ?        00:00:00 ps -ef

Now I detach from container using CTR+p and CTR+q sequence and container is detached.

Now I reattach using the container id and I see the same pid of /bin/bash

root@78c2e4a46b58:/# [root@ip-10-0-1-153 centos]# docker attach 78c2e4a46b58
root@78c2e4a46b58:/# ps -ef
UID        PID  PPID  C STIME TTY          TIME CMD
root         1     0  0 03:24 ?        00:00:00 bash
root        10     0  0 03:24 ?        00:00:00 /bin/bash
root        21     1  0 03:25 ?        00:00:00 ps -ef
root@78c2e4a46b58:/#    

I hope you're using CTR+p CTR+q sequence to detach from the container.

Answer 2

You can't. While the docker exec documentation suggests it supports the same "detach" key sequence as docker run , the exec'd process doesn't have any Docker-level identity (beyond its host and container pids) and there's no way to re-attach to that shell.

(In the Docker API, "exec instance" is an actual object so this isn't technically impossible; the CLI just has no support for it.)

The workflow you're describing sounds more like what you'd run with screen or tmux in a virtual machine.