I wrote application for linux which uses Qt5.
But when I am trying to launch it on the linux without Qt SDK installed, the output in console is:
Failed to load platform plugin "xcb". Available platforms are:
How can I fix this? May be I need to copy some plugin file?
When I use ubuntu with Qt5 installed, but I rename Qt directory, the same problem occurs. So, it uses some file from Qt directory...
UPDATE:
when I create in the app dir "platforms" folder with the file libqxcb.so, the app still doesnot start, but the error message changes:
Failed to load platform plugin "xcb". Available platforms are:
xcb
How can this happen? How can platform plugin be available but can't be loaded?
Use ldd (man ldd) to show shared library dependencies. Running this on libqxcb.so
.../platforms$ ldd libqxcb.so
shows that xcb depends on libQt5DBus.so.5 in addition to libQt5Core.so.5 and libQt5Gui.so.5 (and many other system libs). Add libQt5DBus.so.5 to your collection of shared libs and you should be ready to move on.
As was posted earlier, you need to make sure you install the platform plugins when you deploy your application. Depending on how you want to deploy things, there are two methods to tell your application where the platform plugins (e.g. platforms/plugins/libqxcb.so) are at runtime which may work for you.
The first is to export the path to the directory through the QT_QPA_PLATFORM_PLUGIN_PATH variable.
QT_QPA_PLATFORM_PLUGIN_PATH=path/to/plugins ./my_qt_app
or
export QT_QPA_PLATFORM_PLUGIN_PATH=path/to/plugins
./my_qt_app
The other option, which I prefer is to create a qt.conf file in the same directory as your executable. The contents of which would be:
[Paths]
Plugins=/path/to/plugins
More information regarding this can be found here and at using qt.conf
I tried to start my binary, compiled with Qt 5.7, on Ubuntu 16.04 LTS where Qt 5.5 is preinstalled. It didn't work.
At first, I inspected the binary itself with ldd as was suggested here, and satisfied all "not found" dependencies. Then this notorious This application failed to start because it could not find or load the Qt platform plugin "xcb" error was thrown.
How to resolve this in Linux
Firstly you should create platforms directory where your binary is, because it is the place where Qt looks for XCB library. Copy libqxcb.so there. I wonder why authors of other answers didn't mention this.
Then you may want to run your binary with QT_DEBUG_PLUGINS=1 environment variable set to check which dependencies of libqxcb.so are not satisfied. (You may also use ldd for this as suggested in the accepted answer).
The command output may look like this:
me#xerus:/media/sf_Qt/Package$ LD_LIBRARY_PATH=. QT_DEBUG_PLUGINS=1 ./Binary
QFactoryLoader::QFactoryLoader() checking directory path "/media/sf_Qt/Package/platforms" ...
QFactoryLoader::QFactoryLoader() looking at "/media/sf_Qt/Package/platforms/libqxcb.so"
Found metadata in lib /media/sf_Qt/Package/platforms/libqxcb.so, metadata=
{
"IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
"MetaData": {
"Keys": [
"xcb"
]
},
"className": "QXcbIntegrationPlugin",
"debug": false,
"version": 329472
}
Got keys from plugin meta data ("xcb")
loaded library "/media/sf_Qt/Package/platforms/libqxcb.so"
QLibraryPrivate::loadPlugin failed on "/media/sf_Qt/Package/platforms/libqxcb.so" : "Cannot load library /media/sf_Qt/Package/platforms/libqxcb.so: (/usr/lib/x86_64-linux-gnu/libQt5DBus.so.5: version `Qt_5' not found (required by ./libQt5XcbQpa.so.5))"
This application failed to start because it could not find or load the Qt platform plugin "xcb"
in "".
Available platform plugins are: xcb.
Reinstalling the application may fix this problem.
Aborted (core dumped)
Note the failing libQt5DBus.so.5 library. Copy it to your libraries path, in my case it was the same directory where my binary is (hence LD_LIBRARY_PATH=.). Repeat this process until all dependencies are satisfied.
P.S. thanks to the author of this answer for QT_DEBUG_PLUGINS=1.
I tried the main parts of each answer, to no avail. What finally fixed it for me was to export the following environment variables:
LD_LIBRARY_PATH=/usr/local/lib:~/Qt/5.9.1/gcc_64/lib
QT_QPA_PLATFORM_PLUGIN_PATH=~/Qt/5.9.1/gcc_64/plugins/
Ubuntu 16.04 64bit.
I got the problem for apparently no reasons. The night before I watched a movie on my VideoLan instance, that night I would like to watch another one with VideoLan. VLC just didn't want to run because of the error into the question.
I google a bit and I found the solution it solved my problem: from now on, VLC is runnable just like before. The solution is this comand:
sudo ln -sf /usr/lib/x86_64-linux-gnu/qt5/plugins/platforms/ /usr/bin/
I am not able to explain what are its consequencies, but I know it creates some missing symbolic link.
Since version 5, Qt uses a platform abstraction system (QPA) to abstract from the underlying platform.
The implementation for each platform is provided by plugins. For X11 it is the XCB plugin. See Qt for X11 requirements for more information about the dependencies.
There might be many causes to this problem. The key is to use
export QT_DEBUG_PLUGINS=1
before you run your Qt application. Then, inspect the output, which will point you to the direction of the error. In my case it was:
Cannot load library /opt/nao/plugins/platforms/libqxcb.so: (/opt/nao/bin/../lib/libz.so.1: version `ZLIB_1.2.9' not found (required by /usr/lib/x86_64-linux-gnu/libpng16.so.16))
But that is solved in different threads. See for instance https://stackoverflow.com/a/50097275/2408964.
Probably this information will help. I was on Ubuntu 18.04 and when I tried to install Krita, using the ppa method, I got this error:
This application failed to start because it could not find or load the Qt platform plugin "xcb" in "".
Available platform plugins are: linuxfb, minimal, minimalegl, offscreen, wayland-egl, wayland, xcb.
Reinstalling the application may fix this problem.
Aborted
I tried all the solutions that I found in this thread and other webs without any success.
Finally, I found a post where the author mention that is possible to activate the debugging tool of qt5 using this simple command:
export QT_DEBUG_PLUGINS=1
After adding this command I run again krita I got the same error, however this time I knew the cause of that error.
libxcb-xinerama.so.0: cannot open shared object file: No such file or directory.
This error prevents to the "xcb" to load properly. So, the solution will be install the `libxcb-xinerama.so.0" right? However, when I run the command:
sudo apt install libxcb-xinerama
The lib was already installed. Now what Teo? Well, then I used an old trick :) Yeah, that one --reinstall
sudo apt install --reinstall libxcb-xinerama
TLDR: This last command solved my problem.
I ran into a very similar problem with the same error message. First, debug some by turning on the Qt Debug printer with the command line command:
export QT_DEBUG_PLUGINS=1
and rerun the application. For me this revealed the following:
"Cannot load library /home/.../miniconda3/lib/python3.7/site-packages/PyQt5/Qt/plugins/platforms/libqxcb.so: (libxkbcommon-x11.so.0: cannot open shared object file: No such file or directory)"
"Cannot load library /home/.../miniconda3/lib/python3.7/site-packages/PyQt5/Qt/plugins/platforms/libqxcb.so: (libxkbcommon-x11.so.0: cannot open shared object file: No such file or directory)"
Indeed, I was missing libxkbcommon-x11.so.0 and libxkbcommon-x11.so.0. Next, check your architecture using dpkg from the linux command line. (For me, the command "arch" gave a different and unhelpful result)
dpkg --print-architecture #result for me: amd64
I then googled "libxkbcommon-x11.so.0 ubuntu 18.04 amd64", and likewise for libxkbcommon-x11.so.0, which yields those packages on packages.ubuntu.com. That told me, in retrospect unsurprisingly, I'm missing packages called libxkbcommon-x11-0 and libxkbcommon0, and that installing those packages will include the needed files, but the dev versions will not. Then the solution:
sudo apt-get update
sudo apt-get install libxkbcommon0
sudo apt-get install libxkbcommon-x11-0
So, I spent about a day trying to figure out what was the issue; tried all the proposed solutions, but none of that worked like installing xcb libs or exporting Qt plugins folder. The solution that suggested to use QT_DEBUG_PLUGINS=1 to debug the issue didn't provide me a direct insight like in the answer - instead I was getting something about unresolved symbols within Qt5Core.
That gave me a hint, though: what if it's trying to use different files from different Qt installations? On my machine I had standard version installed in /home/username/Qt/ and some local builds within my project that I compiled by myself (I have other custom built kits as well in other locations). Whenever I tried to use any of the kits (installed by Qt maintenance tool or built by myself), I would get an "xcb error".
The solution was simple: provide the Qt path through CMAKE_PREFIX_PATH and not though Qt5_DIR as I did, and it solved the problem. Example:
cmake .. -DCMAKE_PREFIX_PATH=/home/username/Qt/5.11.1/gcc_64
I faced the same problem when after installing Viber. It had all required qt libraries in /opt/viber/plugins/.
I checked dependencies of /opt/viber/plugins/platforms/libqxcb.so and found missing dependencies. They were libxcb-render.so.0, libxcb-image.so.0, libxcb-icccm.so.4, libxcb-xkb.so.1
So I resolved my issue by installing missing packages with this libraries:
apt-get install libxcb-xkb1 libxcb-icccm4 libxcb-image0 libxcb-render-util0
I like the solution with qt.conf.
Put qt.conf near to the executable with next lines:
[Paths]
Prefix = /path/to/qtbase
And it works like a charm :^)
For a working example:
[Paths]
Prefix = /home/user/SDKS/Qt/5.6.2/5.6/gcc_64/
The documentation on this is here: https://doc.qt.io/qt-5/qt-conf.html
All you need to do is
pip uninstall PyQt5
and
conda install pyqt
Most of the problem of pyqt can be fixed by this simplest solution.
In my case, I needed to deploy two Qt apps on an Ubuntu virtualbox guest. One was command-line ("app"), the other GUI_based ("app_GUI").
I used "ldd app" to find out what the required libs are, and copied them
to the Ubuntu guest.
While the command-line executable "app" worked ok, the GUI-based executable crashed, giving
the "Failed to load platform plugin "xcb" error. I checked ldd for libxcb.so, but this too had no missing dependencies.
The problem seemed to be that while I did copy all the right libraries I accidentally had copied also libraries that were already present at the guest system.. meaning that (a) they were unnecessary to copy them in the first place and (b) worse, copying them produced incompatibilities between the install libraries.
Worse still, they were undetectable by ldd like I said..
The solution? Make sure that you copy libraries shown as missing by ldd and absolutely no extra libraries.
In my case missing header files were the reason libxcb was not built by Qt. Installing them according to https://wiki.qt.io/Building_Qt_5_from_Git#Linux.2FX11 resolved the issue:
yum install libxcb libxcb-devel xcb-util xcb-util-devel mesa-libGL-devel libxkbcommon-devel
Folks trying to get this started on Ubuntu 20.04 please try to run this and see if this solves the problem. This worked for me
sudo apt-get update -y
sudo apt-get install -y libxcb-xinerama0
I link all Qt stuff statically to the generic Linux builds of my open source projects. It makes life a bit easier. You just need to build static versions of Qt libraries first. Of course this cannot be applied to closed source software due to licensing issues. The deployment of Qt5 apps on Linux is currently a bit problematic, because Ubuntu 12.04, for example, doesn't have Qt5 libraries in the package repositories.
I had this problem, and on a hunch I removed the Qt Configs from my environment. I.e.,
rm -rf ~/.config/Qt*
Then I started qtcreator and it reconfigured itself with the existing state of the machine. It no longer remembered where my projects were, but that just meant I had to browse to them "for the first time" again.
But more importantly it built itself a coherent set of library paths, so I could rebuild and run my project executables again without the xcb or qxcb libraries going missing.
I faced the same situation, but on a Ubuntu 20.04 VM.
TL;DR: Check file permissions.
What I did:
I copied the Qt libs required to /usr/local/lib/x86_64-linux-gnu/ and added it to LD_LIBRARY_PATH
I copied the platforms folder from Qt to my application directory and added it to QT_PLUGIN_PATH
I ran ldd on the executable and in the offending libqxcb.so (ldd libqxcb.so), and it complains about some dependencies although ldconfig listed them as found.
linux-vdso.so.1 (0x00007ffee19af000)
libQt5XcbQpa.so.5 => not found
libfontconfig.so.1 => /lib/x86_64-linux-gnu/libfontconfig.so.1 (0x00007f7cb18fb000)
libfreetype.so.6 => /lib/x86_64-linux-gnu/libfreetype.so.6 (0x00007f7cb183c000)
libz.so.1 => /lib/x86_64-linux-gnu/libz.so.1 (0x00007f7cb1820000)
libQt5Gui.so.5 => /usr/local/lib/x86_64-linux-gnu/libQt5Gui.so.5 (0x00007f7cb0fd4000)
libQt5DBus.so.5 => not found
I used export QT_DEBUG_PLUGINS=1 for further info. It complains about missing files, although they are there.
What I found:
For some reason, when copying to the VM through the shared folder the files permissions were not the correct ones.
Thus, I ran: sudo chmod 775 * on the libs and voilà.
I solved the issue through this https://github.com/NVlabs/instant-ngp/discussions/300
pip uninstall opencv-python
pip install opencv-python-headless
This seems to have been a problem with the cv2 Python package and how it loops in Qt
sudo ln -sf /usr/lib/...."adapt-it"..../qt5/plugins/platforms/ /usr/bin/
It creates the symbolic link it's missed. Good for QT ! Good for VLC !!
I met a problem when I try to install QEMU with spice support.
It works well if I install spice-server with yum. In this case when I type ./configure --enable-spice in root directory of QEMU's source codes, the spice-server can be detected correctly.
But now I want to install spice-server by compiling its source codes, cause I have some work to do with it.
I tried ./configure; make; make install and ./configure --prefix=/usr; make; make install. QEMU couldn't find spice-server installed in neither way. I just got
ERROR: User requested feature spice
configure was not able to find it.
Install spice-server(>=0.12.0) and spice-protocol(>=0.12.3) devel
returned.
I don't have this problem in ubuntu, I don't know how to fix it in a CentOS server. Does anybody have a solution?
I guess you are trying to build qemu with spice from source code.
That involves many dependences and configurations.
Especially while you have system-installed 'qemu' running.
Maybe https://github.com/grizzlybears/sqb can help you.
It is a set of helper scripts to automatically do the follwing:
Install build depend.
Get code from offical repository
Get 'fedora base cloud image' as test image
Autogen/configure/build qemu with spice in local dir, touch nothing in system
5.Run test VM using our hand-made 'qemu'
Open spice console to the VM, if you have 'spice-gtk-tools' installed
You should first clone spice-protocol manually and execute ./autogen.sh && ./configure &&make &&make install and export the PKG_CONFIG_PATH export PKG_CONFIG_PATH={your pkg config path}
I'm following a tutorial from this website: Monetizing Game Apps by Todd Perkins
Access to all the files are not required for the questions I'm asking. I have done research on how to solve this on stack overflow and discussed it below
I have followed the tutorial and it has asked me to:
Install Cygwin
Download Cocos2dx-2.0.1(I know this is old, but I don't want to deal with deprecating problems until I'm more confident with the environment)
Run create-android-project.bat(works fine).
Open project I created- and move to proj.android and run build_native.sh in Cygwin.
Then I open up cygwin.bat, navigate to myproject/proj.android and run ./build_native.sh
Problem:
$ ./build_native.sh
Using prebuilt externals
./build_native.sh: line 74: /cygdrive/c/android-ndk-r9c-windows-x86_64/ndk-build: No such file or directory
So I looked into the files and double-checked my changes:
In create-android-project.bat I modified the following variables:
set _CYGBIN=c:\Cygwin64\bin
set _ANDROIDTOOLS=c:\Program Files (x86)\ADT\adt-bundle-windows-x86_64-20130219\sdk\tools
set _NDKROOT=c:\android-ndk-r9c-windows-x86_64
Check line 74 that cygwin complained about in myproject/proj.android/build_native.sh:
echo "Using prebuilt externals"
$NDK_ROOT/ndk-build -C $GAME_ANDROID_ROOT \
NDK_MODULE_PATH=${COCOS2DX_ROOT}:${COCOS2DX_ROOT}/cocos2dx/platform/third_party/android/prebuilt
Double check what NDK_ROOT is pointing to in build_native.sh:
NDK_ROOT=/cygdrive/c/android-ndk-r9c-windows-x86_64
COCOS2DX_ROOT=/cygdrive/c/Users/DarkRaveDev/Documents/cocos2d-x-2.0.1
GAME_ROOT=$COCOS2DX_ROOT/chaara
GAME_ANDROID_ROOT=$GAME_ROOT/proj.android
RESOURCE_ROOT=$GAME_ROOT/Resources
My Research:
I surfed SO for quite some time and tried the following from SO:
EOL Conversion in Notepad++ so LF works for windows for the build_native.sh
An answer somewhere said I need to install the make package when installing cygwin.. I'm not getting this problem, so I'm not sure if this applies.
I have searched many ways to set path - NDK_ROOT
QUESTION:
What exactly am I doing wrong? Is it the variables are badly set or is cygwin not properly installed?
Thank you to everyone who commented! :)
This is what I ended up doing.
Reinstall Cygwin : When you get to the select packages to install page, make sure to find DEVEL and change the install action from default to install. I know its a lot of megs but it's easier than combing through it. If you do want to comb through it and get only what you need, I suggest using this website: Installing a c++ compiler for windows
Make your paths simple : Like user2359247 suggested.
Finally run the create_android.bat, open your android project. Keep the path location of your build_native.sh file in mind and open your cygwin terminal.
Navigate to the path in cygwin, and run the file with sh build_native.sh: At this point everything was quite smooth sailing.
NOTE:
Also I kept using my version of ndk which is r9 instead of r8 in the tutorial, it didn't give me any hiccups.
Thank you SO!
I am trying to get Mono working on nginx with fastCGI.
I have done a fresh install of CentOS 6, and performed all the updates. I then installed nginx, and opened up the firewalls I needed. I can now see the simple HTML page from nginx without a problem.
I then followed this tutorial for installing Mono via Git :
https://stackoverflow.com/a/13424880/221456
libgdiplus installed fine
mono installed fine
xsp, when I run autogen (with the prefix), gives me this error :
checking for MONO_MODULE... configure: error: Package requirements
(mono >= 2.10.0) were not met:
No package 'mono' found
I did a bit of searching, and the only thing I could find was to run this command :
export PKG_CONFIG_PATH=/usr/local/lib/pkgconfig
Which I have tried, however I still get the exact same error message.
What am I missing?
The problem is with the variable
export PKG_CONFIG_PATH=/usr/local/lib/pkgconfig
the correct is
export PKG_CONFIG_PATH=/usr/lib/pkgconfig
because you compile with the with the prefix. /usr
I am trying to install Code::Blocks 10.05 from (non-SVN) sources (codeblocks-10.05-src.tar.bz2). My OS is Ubuntu 11.04. I needed to download and install wxWidgets first (I now have wxGTK-2.8.12), which seemed to work. I compiled it according to these instructions:
http://wiki.codeblocks.org/index.php?title=Installing_Code::Blocks_from_source_on_Linux
Then I configured C::B with
./configure --with-wx-config=/opt/wx/2.8/bin/wx-config
and ran
export LDFLAGS="-Wl,-R /opt/wx/2.8/lib"
make
sudo -i
make install
When trying to run C::B, I get the following error:
codeblocks: error while loading shared libraries: libwx_gtk2u-2.8.so.0: cannot open shared object file: No such file or directory
The same question was asked here: error while loading shared libraries, but the suggested solution (namely adding the wxWidgets config to the options passed to configure) didn't work for me.
The output of wx-config --prefix is /opt/wx/2.8,
The output of wx-config --libs is -L/opt/wx/2.8/lib -pthread -lwx_gtk2u-2.8,
and that of which wx-config is /opt/wx/2.8/bin/wx-config.
I looked for the library and found /opt/wx/lib/libwx_gtk2u-2.8.so.0 to be a link to libwx_gtk2u-2.8.so.0.8.0 in the same folder.
What might be wrong here?
The problem is that the program cannot find the WX widgets libraries at run time. You will need to set your LD_LIBRARY_PATH variable to include the location of wxWidgets like this:
LD_LIBRARY_PATH=/opt/wx/2.8/lib ./codeblocks
The reason why its failing is because you compiled codeblocks against wxWidgets found in /opt/ and not the one installed in /usr/; the program doesn't know to look in /opt for the wx libraries.
Probably the easiest way to get code::blocks up and running on Ubuntu is to just install it via the Synaptic Package Manager. Just type in codeblocks into 'Quick search'. Find codeblocks on the list and just right-click to mark for install. Any dependencies and missing libraries needed will automatically be handled and installed by Synaptic as necessary.
If you're interested in trying the C::B nightly builds on Ubuntu then you'll want to checkout Jens' unofficial debian-repository here.
You can visit Why do I have to define LD_LIBRARY_PATH with an export every time I run my application? for a more generic case. For a particular case like yours you can follow the below given steps
If you had installed wxGTK then you would see the file in /usr/local/lib. You would get this error when the the above path is not as part of the makefile. I received this error while starting wxFormBuilder after building from source on CentOS. There are 2 approaches.
Approach 1: Putting the path in .bashrc
gedit /home/{your-username}/.bashrc
Then after the line # User specific aliases and functions paste the following
export $LD_LIBRARY_PATH=/usr/local/lib.
This would work for fine but for the current login, but for other users like root you might have to do the same in the respective .bashrc files.
Approach 2: Creating your own conf files
cd /etc/ld.so.conf.d
gedit wxformbuilder.conf
Give the path /usr/local/lib and save the file.
ldconfig (To update the library path).