Running Qt apps inside a 18.04 container crashes

[Andrew Hayzen]

What happened:
1) Install a container system (eg Docker, LXD) - I'm using Docker
2) Create a container which is Ubuntu 18.04
3) Install a Qt app, eg qtcreator, inside the container
4) Run the container so that it shows the hosts X11 socket
5) Notice that the application fails to start

What I expected to happen:
At step 5 for the application to start.

Note that the same steps work fine for Ubuntu 16.04 and 17.10 - and if it matters my host is 17.10.

Here is a stacktrace of the crash https://pastebin.ubuntu.com/p/WKKGmxqqSx/

Here is a Dockerfile that reproduces the issue https://pastebin.ubuntu.com/p/nzmJRfPYVc/ to use this make a Dockerfile in an empty folder with the pastebin contents, then simply run the following commands in that folder

$ sudo apt install docker.io
$ sudo docker build -t qtbug .
$ sudo docker run --rm -ti -e DISPLAY --net=host --cap-add=SYS_PTRACE --security-opt seccomp=unconfined qtbug

This should enter you into the gdb session.

[Andrew Hayzen (ahayzen)]

Note I have tried using the .run offline installer of Qt 5.6/5.9/5.11, what seems to happen is that they work on Ubuntu 16.04, 17.10 but fail on 18.04 - this is the stacktrace for reference https://pastebin.ubuntu.com/p/Yzj5gsmwQ3/

So it seems possible that it might be some underlying change to the platform (maybe something like dbus? or a new config/dir I need to enable).

Furthermore it looks like this issue may affect Qt applications when they try to run as a snap under the core18 snap. https://github.com/snapcore/core18/issues/4

[Dmitry Shachnev (mitya57)]

Interesting that I cannot reproduce this on Debian sid, which has a newer Docker.io version (18.03.1 vs. 17.12.1).

Can you try starting dbus before running the application, to see if that helps?

$ sudo /etc/init.d/dbus start # Start the system bus
$ dbus-daemon --session --fork # And the session bus

[Andrew Hayzen (ahayzen)]

@mitya57, Thanks for having a look at this. I have tried starting dbus and dbus-daemon as you have described before running QtCreator - but it still fails in the same way :-/

I have also tried installing dbus-x11 and executing $ export $(dbus-launch) to set the env vars, but this still results in the same :-/

Interesting that Debian sid doesn't appear to be affected.

[Timo Jyrinki (timo-jyrinki)]

https://bugreports.qt.io/browse/QTBUG-70447 notes that a newer Docker fixes it.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.