problem with qt.qpa.plugin: running on a docker in Kubuntu

john_hobbyist

Hello, I have built a python application with PyQt that works perfectly when I run it on Kubuntu 20.04.1 LTS but when I try to put the application on a docker script and execute it, I got the following error:

qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "" even though it was found.
This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.

Available platform plugins are: eglfs, linuxfb, minimal, minimalegl, offscreen, vnc, wayland-egl, wayland, wayland-xcomposite-egl, wayland-xcomposite-glx, webgl, xcb.

The docker is compiled without any errors. But when I try to run the docker I take the above error.

What should I do?

@update: This command

ldd /usr/lib/x86_64-linux-gnu/qt5/plugins/platforms/libqxcb.so

shows me a lot of files

SGaist

Hi,

Docker does not have access do your X server so your application can't start.

For more information, start it with the QT_DEBUG_PLUGINS environment variable set to 1.

john_hobbyist

I included this command inside the docker script:

QT_DEBUG_PLUGINS=1

I try to build the script and I got this:

Sending build context to Docker daemon  60.93kB
Error response from daemon: Dockerfile parse error line 42: unknown instruction: QT_DEBUG_PLUGINS=1

SGaist

Because that is not a valid command, if you want to include an environment variable in your Dockerfile, use the ENV command.

john_hobbyist

Ok. I got answer with data. What should I look for?

SGaist

The entry related to xcb, you'll have some information about why it failed to load.

john_hobbyist

This is what I found related to xcb:

Got keys from plugin meta data ("webgl")
QFactoryLoader::QFactoryLoader() looking at "/usr/local/lib/python3.9/site-packages/PyQt5/Qt5/plugins/platforms/libqxcb.so"
Found metadata in lib /usr/local/lib/python3.9/site-packages/PyQt5/Qt5/plugins/platforms/libqxcb.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "xcb"
        ]
    },
    "archreq": 0,
    "className": "QXcbIntegrationPlugin",
    "debug": false,
    "version": 331520
}


Got keys from plugin meta data ("xcb")
QFactoryLoader::QFactoryLoader() checking directory path "/usr/local/bin/platforms" ...
Cannot load library /usr/local/lib/python3.9/site-packages/PyQt5/Qt5/plugins/platforms/libqxcb.so: (libxcb-util.so.1: cannot open shared object file: No such file or directory)
QLibraryPrivate::loadPlugin failed on "/usr/local/lib/python3.9/site-packages/PyQt5/Qt5/plugins/platforms/libqxcb.so" : "Cannot load library /usr/local/lib/python3.9/site-packages/PyQt5/Qt5/plugins/platforms/libqxcb.so: (libxcb-util.so.1: cannot open shared object file: No such file or directory)"
qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "" even though it was found.
This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.

Available platform plugins are: eglfs, linuxfb, minimal, minimalegl, offscreen, vnc, wayland-egl, wayland, wayland-xcomposite-egl, wayland-xcomposite-glx, webgl, xcb.

SGaist

@john_hobbyist said in problem with qt.qpa.plugin: running on a docker in Kubuntu:

libxcb-util.so.1

You are missing that file in your Docker image.

john_hobbyist

Do I need to install a specific package? Or only the non-existing file? I suppose

pip3 install ...

??

SGaist

No this is a system library that you need to install using your image distribution package manager.

john_hobbyist

How can I achieve this?

SGaist

As I wrote above, this is done using the package manager that is provided by the distribution you use as a base for your Docker image. Use a RUN command for that.

john_hobbyist

After google search, I found and I tried this command:

RUN apt-get install -y libxcb-util1

It does not work:

E: Unable to locate package libxcb-util1
The command '/bin/sh -c apt-get install -y libxcb-util1' returned a non-zero code: 100

eyllanesc

@john_hobbyist use: RUN apt-get install -y '^libxcb.*-dev' libx11-xcb-dev libglu1-mesa-dev libxrender-dev libxi-dev libxkbcommon-dev libxkbcommon-x11-dev and show the new log

john_hobbyist

QFactoryLoader::QFactoryLoader() checking directory path "/usr/local/lib/python3.9/site-packages/PyQt5/Qt5/plugins/platforms" ...
QFactoryLoader::QFactoryLoader() looking at "/usr/local/lib/python3.9/site-packages/PyQt5/Qt5/plugins/platforms/libqeglfs.so"
Found metadata in lib /usr/local/lib/python3.9/site-packages/PyQt5/Qt5/plugins/platforms/libqeglfs.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "eglfs"
        ]
    },
    "archreq": 0,
    "className": "QEglFSIntegrationPlugin",
    "debug": false,
    "version": 331520
}


Got keys from plugin meta data ("eglfs")
QFactoryLoader::QFactoryLoader() looking at "/usr/local/lib/python3.9/site-packages/PyQt5/Qt5/plugins/platforms/libqlinuxfb.so"
Found metadata in lib /usr/local/lib/python3.9/site-packages/PyQt5/Qt5/plugins/platforms/libqlinuxfb.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "linuxfb"
        ]
    },
    "archreq": 0,
    "className": "QLinuxFbIntegrationPlugin",
    "debug": false,
    "version": 331520
}


Got keys from plugin meta data ("linuxfb")
QFactoryLoader::QFactoryLoader() looking at "/usr/local/lib/python3.9/site-packages/PyQt5/Qt5/plugins/platforms/libqminimal.so"
Found metadata in lib /usr/local/lib/python3.9/site-packages/PyQt5/Qt5/plugins/platforms/libqminimal.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "minimal"
        ]
    },
    "archreq": 0,
    "className": "QMinimalIntegrationPlugin",
    "debug": false,
    "version": 331520
}


Got keys from plugin meta data ("minimal")
QFactoryLoader::QFactoryLoader() looking at "/usr/local/lib/python3.9/site-packages/PyQt5/Qt5/plugins/platforms/libqminimalegl.so"
Found metadata in lib /usr/local/lib/python3.9/site-packages/PyQt5/Qt5/plugins/platforms/libqminimalegl.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "minimalegl"
        ]
    },
    "archreq": 0,
    "className": "QMinimalEglIntegrationPlugin",
    "debug": false,
    "version": 331520
}


Got keys from plugin meta data ("minimalegl")
QFactoryLoader::QFactoryLoader() looking at "/usr/local/lib/python3.9/site-packages/PyQt5/Qt5/plugins/platforms/libqoffscreen.so"
Found metadata in lib /usr/local/lib/python3.9/site-packages/PyQt5/Qt5/plugins/platforms/libqoffscreen.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "offscreen"
        ]
    },
    "archreq": 0,
    "className": "QOffscreenIntegrationPlugin",
    "debug": false,
    "version": 331520
}


Got keys from plugin meta data ("offscreen")
QFactoryLoader::QFactoryLoader() looking at "/usr/local/lib/python3.9/site-packages/PyQt5/Qt5/plugins/platforms/libqvnc.so"
Found metadata in lib /usr/local/lib/python3.9/site-packages/PyQt5/Qt5/plugins/platforms/libqvnc.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "vnc"
        ]
    },
    "archreq": 0,
    "className": "QVncIntegrationPlugin",
    "debug": false,
    "version": 331520
}


Got keys from plugin meta data ("vnc")
QFactoryLoader::QFactoryLoader() looking at "/usr/local/lib/python3.9/site-packages/PyQt5/Qt5/plugins/platforms/libqwayland-egl.so"
Found metadata in lib /usr/local/lib/python3.9/site-packages/PyQt5/Qt5/plugins/platforms/libqwayland-egl.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "wayland-egl"
        ]
    },
    "archreq": 0,
    "className": "QWaylandEglPlatformIntegrationPlugin",
    "debug": false,
    "version": 331520
}


Got keys from plugin meta data ("wayland-egl")
QFactoryLoader::QFactoryLoader() looking at "/usr/local/lib/python3.9/site-packages/PyQt5/Qt5/plugins/platforms/libqwayland-generic.so"
Found metadata in lib /usr/local/lib/python3.9/site-packages/PyQt5/Qt5/plugins/platforms/libqwayland-generic.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "wayland"
        ]
    },
    "archreq": 0,
    "className": "QWaylandIntegrationPlugin",
    "debug": false,
    "version": 331520
}


Got keys from plugin meta data ("wayland")
QFactoryLoader::QFactoryLoader() looking at "/usr/local/lib/python3.9/site-packages/PyQt5/Qt5/plugins/platforms/libqwayland-xcomposite-egl.so"
Found metadata in lib /usr/local/lib/python3.9/site-packages/PyQt5/Qt5/plugins/platforms/libqwayland-xcomposite-egl.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "wayland-xcomposite-egl"
        ]
    },
    "archreq": 0,
    "className": "QWaylandXCompositeEglPlatformIntegrationPlugin",
    "debug": false,
    "version": 331520
}


Got keys from plugin meta data ("wayland-xcomposite-egl")
QFactoryLoader::QFactoryLoader() looking at "/usr/local/lib/python3.9/site-packages/PyQt5/Qt5/plugins/platforms/libqwayland-xcomposite-glx.so"
Found metadata in lib /usr/local/lib/python3.9/site-packages/PyQt5/Qt5/plugins/platforms/libqwayland-xcomposite-glx.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "wayland-xcomposite-glx"
        ]
    },
    "archreq": 0,
    "className": "QWaylandXCompositeGlxPlatformIntegrationPlugin",
    "debug": false,
    "version": 331520
}


Got keys from plugin meta data ("wayland-xcomposite-glx")
QFactoryLoader::QFactoryLoader() looking at "/usr/local/lib/python3.9/site-packages/PyQt5/Qt5/plugins/platforms/libqwebgl.so"
Found metadata in lib /usr/local/lib/python3.9/site-packages/PyQt5/Qt5/plugins/platforms/libqwebgl.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "webgl"
        ]
    },
    "archreq": 0,
    "className": "QWebGLIntegrationPlugin",
    "debug": false,
    "version": 331520
}


Got keys from plugin meta data ("webgl")
QFactoryLoader::QFactoryLoader() looking at "/usr/local/lib/python3.9/site-packages/PyQt5/Qt5/plugins/platforms/libqxcb.so"
Found metadata in lib /usr/local/lib/python3.9/site-packages/PyQt5/Qt5/plugins/platforms/libqxcb.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "xcb"
        ]
    },
    "archreq": 0,
    "className": "QXcbIntegrationPlugin",
    "debug": false,
    "version": 331520
}


Got keys from plugin meta data ("xcb")
QFactoryLoader::QFactoryLoader() checking directory path "/usr/local/bin/platforms" ...
Cannot load library /usr/local/lib/python3.9/site-packages/PyQt5/Qt5/plugins/platforms/libqxcb.so: (libxcb-util.so.1: cannot open shared object file: No such file or directory)
QLibraryPrivate::loadPlugin failed on "/usr/local/lib/python3.9/site-packages/PyQt5/Qt5/plugins/platforms/libqxcb.so" : "Cannot load library /usr/local/lib/python3.9/site-packages/PyQt5/Qt5/plugins/platforms/libqxcb.so: (libxcb-util.so.1: cannot open shared object file: No such file or directory)"
qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "" even though it was found.
This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.

Available platform plugins are: eglfs, linuxfb, minimal, minimalegl, offscreen, vnc, wayland-egl, wayland, wayland-xcomposite-egl, wayland-xcomposite-glx, webgl, xcb.

eyllanesc

@john_hobbyist said RUN apt-get install -y libxcb-util-dev, also show the Dockerfile

john_hobbyist

@eyllanesc said in problem with qt.qpa.plugin: running on a docker in Kubuntu:

RUN apt-get install -y libxcb-util-dev

Step 19/21 : RUN apt-get install -y libxcb-util-dev
 ---> Running in ......
Reading package lists...
Building dependency tree...
Reading state information...
E: Unable to locate package libxcb-util-dev
The command '/bin/sh -c apt-get install -y libxcb-util-dev' returned a non-zero code: 100

Yes, I saw it now:

FROM python:3

ADD code.py /

RUN pip3 install opencv-python-headless
RUN apt-get update ##[edited]

RUN apt-get install ffmpeg libsm6 libxext6  -y

RUN pip3 install matplotlib

RUN apt-get install python3-pyqt5 -y

RUN pip3 install pyqt5

RUN pip3 install wheel

RUN pip3 install pandas

RUN pip3 install openpyxl

RUN pip3 install geopandas

# RUN apt update -y

# RUN apt install libpq-dev -y

# RUN apt install gdal-bin -y

# RUN apt install libgdal-dev -y

RUN pip3 install numba

# RUN pip3 install GDAL

RUN apt-get install qt5-default -y

RUN pip3 install numpy

RUN ldd /usr/lib/x86_64-linux-gnu/qt5/plugins/platforms/libqxcb.so

RUN apt-get update -y

RUN apt-get install -y '^libxcb.*-dev' libx11-xcb-dev libglu1-mesa-dev libxrender-dev libxi-dev libxkbcommon-dev libxkbcommon-x11-dev 

RUN apt-get install -y libxcb-util-dev

ENV QT_DEBUG_PLUGINS=1

CMD [ "python3", "code.py" ]

Any idea???

eyllanesc

@john_hobbyist change FROM python:3 to FROM ubuntu:latest. "python: 3" uses a minimalistic version of linux that does not have some packages. Also remove RUN apt-get install qt5-default -y and RUN ldd /usr/lib/x86_64-linux-gnu/qt5/plugins/platforms/libqxcb.so. If you can't find the pip command then add first: RUN apt install python3-pip

john_hobbyist

@eyllanesc

Sending build context to Docker daemon  60.93kB
Step 1/19 : FROM ubuntu:latest
 ---> ......
Step 2/19 : ADD code.py /
 ---> Using cache
 ---> .....
Step 3/19 : RUN pip3 install opencv-python-headless
 ---> Running in .....
/bin/sh: 1: pip3: not found
The command '/bin/sh -c pip3 install opencv-python-headless' returned a non-zero code: 127
UbuntuUser@ubuntu:~/Desktop/test/my_new_docker_build$

Does not run more than this step...

eyllanesc

@john_hobbyist mmm, you seem to not fully read my comment: add RUN apt install -y python3-pip before RUN pip3 install opencv-python-headless