Error: cannot set terminal process group (-1): Inappropriate ioctl for device

When I have dumb-init in ENTRYPOINT like this

...
ENTRYPOINT ["/usr/bin/dumb-init"]
...

and then try to run bash with tty and interactively, I get this error:

docker run --rm -t -i dumb_init_image bash
bash: cannot set terminal process group (-1): Inappropriate ioctl for device
...

[javabean]

Unfortunately I still see this error message, using dumb-init 1.2.0 (Ubuntu 16.04, both directly in the host shell, and inside a docker run --rm -ti ubuntu:16.04 bash):

$ ./dumb-init_1.2.0_amd64 bash
bash: cannot set terminal process group (-1): Inappropriate ioctl for device
bash: no job control in this shell
$ exit
$ ./dumb-init_1.2.0_amd64 -c bash
$ exit

Note that tini does not exhibit this problem (i.e. works fine with and without its -g flag).

[chriskuehl]

@alhafoudh still looking into the root cause. I think it’s something we can fix.

For now a workaround is to run in non-setsid mode using -c, e.g.

ENTRYPOINT ["/usr/bin/dumb-init", "-c", "--"]

The only difference behavior-wise is that signals are only forwarded to your direct child. So if you have a process tree like

PID 1: dumb-init
+---- PID 2: python server
    +---- PID 3: worker process
    +---- PID 4: worker process
    +---- PID 5: worker process

when you send docker signal, the signal is only delivered to PID 2 and not everything in the process group (potentially including the workers).

This is usually acceptable behavior since the server is supposed to handle signaling its workers before it dies anyway. Unfortunately there are some exceptions, which is why the default is setsid mode.

I’ll keep looking into this and get back to you.