How to attach to different tty within a docker container?

I find that docker attach command only attach to the first tty(pts/0 or PID 1) of a container that has many ttys.

E.g. If I create a container test0 first:

docker run -it --name test0 ubuntu18.04 /bin/bash

Than press ctrl+p,q, this first bash process will be detached and keep running in the Background.

And than I create a new back-ground shell again by docker exec -it test0 /bin/bash and pressing ctrl+p,q again.

Above sequence will create two ttys within container test0, as listed in docker exec 032 ps -ef:

root         1     0  0 Oct29 pts/0    00:00:00 /bin/bash
root      1491     0  0 00:11 pts/1    00:00:00 /bin/bash
root      1740     0  0 00:59 ?        00:00:00 ps -ef

Every time I try to use docker attach test0 will only result in the attaching to pts/0 which PID is 1. But I still need to do some work under pts/1 or PID 1491. What should I do to attach to the pts/1 which PID is 1491?

BESIDES, I also thought about using tmux or screen within the first tty BUT I wonder if its a good way for docker - docker features in making processes run fast and light-weighted, I don’t know if using tmux to handle processes will slow them down.

docker attach only attaches to pid 1. It’s not usual in docker to have multiple pttys running in a container.

You might consider docker exec -it to start non-pid-1 pttys as required and attach to them.

So appreciate towards your reply, I finally choose to use tmux to solve the problem.