QEMU hangs in Docker after the login prompt

[loic-yvonnet]

In summary, QEMU hangs in the CROPS/Poky Docker container after the login prompt.

The problem may be reproduced from a Ubuntu 18.04 host by following these steps:

• In a terminal, type:

  docker pull crops/poky:ubuntu-18.04
  mkdir workdir
  cd workdir
  git clone git://git.yoctoproject.org/poky
  docker run --name yocto-dev --rm -it \
      -v $PWD/workdir:/workdir \
      crops/poky:ubuntu-18.04 --workdir=/workdir

• In a different terminal, create a file named compile.sh:

  #!/bin/bash
  
  source ./poky/oe-init-build-env > /dev/null
  bitbake core-image-minimal

• Create a file named run.sh:

  #!/bin/bash
  
  source ./poky/oe-init-build-env > /dev/null
  runqemu qemux86-64 core-image-minimal qemuparams="-m 256" slirp nographic

• Finally, type:

  chmod 755 compile.sh
  chmod 755 run.sh
  docker exec -w /workdir -u pokyuser -i yocto-dev bash < compile.sh
  docker exec -w /workdir -u pokyuser -i yocto-dev bash < run.sh

Actual result:

• QEMU boots the core-image-minimal.
• It displays the login prompt.
• After entering "root", QEMU hangs and never displays the prompt.
• It is not possible to execute a command from the emulated OS.

Expected result:

• QEMU boots the core-image-minimal.
• It displays the login prompt.
• After entering "root", QEMU displays the regular prompt.
• It is possible to execute commands in the emulated OS.

On the other hand, compiling and running the core-image-minimal from the Ubuntu 18.04 host in QEMU works as expected.

Is there a workaround to run QEMU from a Docker container?

PS: I am new to the Yocto project and QEMU. It may not be a good idea to run QEMU on top of a Docker container. I am simply trying to see if I can run everything from a container.

[rewitt1]

Hi @loic-yvonnet,

Thanks for the extremely easy to follow instructions on reproducing the issue.

PS: I am new to the Yocto project and QEMU. It may not be a good idea to run QEMU on top of a Docker container. I am simply trying to see if I can run everything from a container.

Running qemu inside of the container should work. I reproduced the issue you mentioned, and I think the hang you are seeing is because there is no tty. If you instead tried to run runqemu in the shell started from docker run, I expect it should work.

You could also copy run.sh into workdir and run docker exec -w /workdir -u pokyuser -it yocto-dev /workdir/run.sh

Unfortunately, I'm unsure if there is a way to use your original command. Because you will likely get the following error if you try using a tty with your original command.

$ sudo docker exec -w /workdir -u pokyuser -it yocto-dev bash < run.sh
the input device is not a TTY

[loic-yvonnet]

Hi @rewitt1,

Many thanks for your quick answer. I confirm that the following worked for me:

You could also copy run.sh into workdir and run docker exec -w /workdir -u pokyuser -it yocto-dev /workdir/run.sh

Thanks a lot.