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 have instaled Cygwin after running MinGW for a while now. But when I try to compile the console gives me:
/usr/lib/gcc/x86_64-pc-cygwin/4.9.2/cc1.exe: error while loading shared libraries: ?: cannot open shared object file: No such file or directory
What does this mean?
I have the same problem and I found the solution.
According to the FAQ of Cygwin
Q: Why is C:\cygwin\usr\bin invisible from windows?
A: Because it does not really exist. In cygwin, /usr/bin is just a link to /bin.
So trying to add "C:\cygwin\usr\bin" to PATH will be in vain.
Add "C:\cygwin64\bin" to PATH instead. Hope this helps :)
You are missing a library, please run cygcheck /usr/lib/gcc/x86_64-pc-cygwin/4.9.2/cc1.exe or ldd /usr/lib/gcc/x86_64-pc-cygwin/4.9.2/cc1.exe to see what is the missing library.
(I'd rather ask a question in the comments first, but I don't have enough reputation yet.)
Your cc1 is unable to load some DLLs it needs to start. Looking at the Cygwin source code, this can be either a library specified in LD_PRELOAD, or -- more probably -- a library the executable depends on. The ? in the error message seems to be the default return value of find_first_notloaded_dll (hookapi.cc), in case the function can't determine what library is missing.
To diagnose the issue, I suggest checking your PATH variable (or even clearing it of any non-Cygwin paths and trying the compilation again) and/or using Dependency Walker to find the missing DLLs (start it from a Cygwin shell, so it can see the same PATH). ldd (included with Cygwin) may also give some clues, but I wouldn't bet on it.
It's possible a clean re-install of Cygwin will be necessary to solve the issue.
Most likely, you are simply missing /usr/bin in the PATH variable.
Adding 'export PATH=/usr/bin:$PATH' to your .bashrc file will solve the issue.
Adding some background info. I had the same problem when building my own program and linking it against graphviz cgraph.dll. Turns out this is related to where windows searches for DLLs (see here: https://msdn.microsoft.com/en-us/library/7d83bc18.aspx) So adding the path of your missing library to PATH should fix the problem.
It is unfortunate that the message doesn't include the name of the library. Luckily cmd.exe DOES give you this name (so it's good for something after all;)
Are you including the path to your lib directory?
Looks like you are not
I'm not very familiar with Cygwin, I mainly use MinGW, but I think the error message speaks for itself
I also came this error on windows machine while executing .exe file generated by scilab2C i.e toolbox for Scilab
For Windows 32 bit Add the environment variable path as follow :
C:\cygwin\usr\i686-pc-cygwin\bin
Hope so this will solve your issue.
Just had this problem trying to compile a package with make and it wanted some cygguile dll file that was just installed along with make.
My solution was I had not only migrated my cygwin64 directory across drives because the sector sizes were mismatched for some reason even though the drivers were both under 2TB and should have been using 512 byte sector sizes.. So I had to install a new system and move files over there, might have had weird permissions on them.
Also had to patch cygwin1.dll end of Jan 2020 because of a recent input problem in ConEmu with Windows 10 1903 build, but just did it again with this working so that doesn't seem to be the issue.
Reinstalling cygwin by deleting that entire directory, taking ownership of it first.., seemed to work now...
(Note: names of the binary and binary and library below are obfuscated to protect the innocent. ;-) The app is proprietary under NDA but the behavior may not depend on it.)
I have a Linux binary which prints the following error when run:
binary: error while loading shared libraries: libshared.so: cannot open shared object file: No such file or directory
Which is confusing on its own since libshared.so is in the LD_LIBRARY_PATH. However,
The library is found correctly when running ldd binary (i.e., the ldd output points to the file location)
The library is found correctly when running strace binary, so that the program manages to print its usage information!
I have never seen an application which behaves differently when run on its own vs in strace, but I figure maybe someone else has seen this happen before? Any ideas how to resolve this?
I don't have the source so I can't rebuild. Running the app in production under strace is probably a non-starter. The OS is RHEL 6.2.
(Old question, but hopefully this will help somebody else)
Under new Linux installations, LD_LIBRARY_PATH is not used by the standard system runtime linker for programs with SUID set. It appears that strace, gdb and friends work differently, and do use LD_LIBRARY_PATH.
For suid programs, all libraries must be found in the system library cache. Check (as root) whether your "missing" library is present using
ldconfig -p | grep <my_library_name>
and, if anything's missing, add it to a new file in /etc/ld.so.conf or ld.so.conf.d/ as appropriate, and then rebuild using
ldconfig -v
Or remove the SUID bit if it's not required, of course.
This really helped me a lot!
I was having a similar problem where libraries were not being picked up properly from the LD_LIBRARY_PATH, even when the ldd command showed all libraries were satisfied. However, when troubleshooting using strace, it was working. In my case, however, the problem was that SGID (set group ID sticky bit being on). When the files were installed, the sysadmin did a recursive chmod that set it on all files (including the executables). Once the SGID was removed on the executables, the libraries were now found without strace and everything worked as it should using the LD_LIBRARY_PATH.
I installed OSX Mavericks to make sure that the application I'm developing can run on this system. I compile with PyInstaller (my build script that uses PYInstaller runs without errors).
The problem is that when I double-click on the executable, I get this error:
Last login: Wed Jan 16 22:56:18 on ttys004
Mac-Pro-de-angelo:~ angelo$ /Users/angelo/miniconda3/envs/apsc/apsc_1_0_0_onefile_mac_osx/apsc ; exit;
objc[5125]: Class RunLoopModeTracker is implemented in both /var/folders/t0/s6_p_gn15798z_8m8w5f6vjm0000gn/T/_MEIWgQ7yV/libQt5Core.5.dylib and /Users/angelo/miniconda3/envs/apsc/lib/libQt5Core.5.6.2.dylib. One of the two will be used. Which one is undefined.
objc[5125]: Class NotificationReceiver is implemented in both /var/folders/t0/s6_p_gn15798z_8m8w5f6vjm0000gn/T/_MEIWgQ7yV/libQt5Widgets.5.dylib and /Users/angelo/miniconda3/envs/apsc/lib/libQt5Widgets.5.6.2.dylib. One of the two will be used. Which one is undefined.
objc[5125]: Class QCocoaPageLayoutDelegate is implemented in both /var/folders/t0/s6_p_gn15798z_8m8w5f6vjm0000gn/T/_MEIWgQ7yV/libQt5PrintSupport.5.dylib and /Users/angelo/miniconda3/envs/apsc/lib/libQt5PrintSupport.5.6.2.dylib. One of the two will be used. Which one is undefined.
objc[5125]: Class QCocoaPrintPanelDelegate is implemented in both /var/folders/t0/s6_p_gn15798z_8m8w5f6vjm0000gn/T/_MEIWgQ7yV/libQt5PrintSupport.5.dylib and /Users/angelo/miniconda3/envs/apsc/lib/libQt5PrintSupport.5.6.2.dylib. One of the two will be used. Which one is undefined.
QObject::moveToThread: Current thread (0x7f9362f5b620) is not the object's thread (0x7f93640b2370).
Cannot move to target thread (0x7f9362f5b620)
You might be loading two sets of Qt binaries into the same process. Check that all plugins are compiled against the right Qt binaries. Export DYLD_PRINT_LIBRARIES=1 and check that only one set of binaries are being loaded.
This application failed to start because it could not find or load the Qt platform plugin "cocoa"
in "".
Available platform plugins are: cocoa, minimal, offscreen.
Reinstalling the application may fix this problem.
Abort trap: 6
logout
[Opération terminée]
If I refer to this post:
pyinstaller + pyqt5: could not find or load "cocoa"
I encounter the same problem but the proposed solution does not work not at my house.
That's how my PYInstaller script is run:
/Users/angelo/miniconda3/envs/apsc/bin/pyinstaller --clean --windowed --onefile --runtime-tmpdir /var/folders/t0/s6_p_gn15798z_8m8w5f6vjm0000gn/T --icon=logo_apsc_256x256.icns --distpath apsc_1_0_0_onefile_mac_osx --name apsc apsc_gui.py
For accuracy my software works fine under MacOSX when launched directly from Python.
Can you help me find a solution?
These are my specifications:
MacOSX 10.9.5
Python 3.4.5, qt-5.6.2, sip-4.18 and pyqt-5.6.0 under Miniconda3-3.8.3
... After ...
I would really like to solve this problem, it's been several days ... and I can not do it.
It has evolved a little but I still have errors and it is still impossible for me to launch my software (the, generated app) under MacOSX after compilation with PyInstaller,
That's what I did:
A symbolic link between libpython3.6m.dylib and libpython3.6.dylib (the latter did not exist in the bin directory of the environment created in miniconda3):
ln -s /Users/angelo/miniconda3/envs/test/lib/libpython3.6m.dylib /Users/angelo/miniconda3/envs/test/lib/libpython3.6.dylib
Then I placed the order:
export DYLD_PRINT_RPATHS=1
It should be noted that I find myself with the error:
21966 ERROR: Can not find path ./libtbb.dylib (needed by /Users/angelo/miniconda3/envs/test/lib/libmkl_tbb_thread.dylib)
The result is a little better but I always find myself with the errors:
objc[2619]: Class RunLoopModeTracker is implemented in both /private/var/folders/t0/s6_p_gn15798z_8m8w5f6vjm0000gn/T/_MEIqjVaY5/libQt5Core.5.dylib and /Users/angelo/miniconda3/envs/test/lib/libQt5Core.5.6.2.dylib. One of the two will be used. Which one is undefined.
objc[2619]: Class NotificationReceiver is implemented in both /private/var/folders/t0/s6_p_gn15798z_8m8w5f6vjm0000gn/T/_MEIqjVaY5/libQt5Widgets.5.dylib and /Users/angelo/miniconda3/envs/test/lib/libQt5Widgets.5.6.2.dylib. One of the two will be used. Which one is undefined.
QObject::moveToThread: Current thread (0x7ff483848540) is not the object's thread (0x7ff48385ab60).
Cannot move to target thread (0x7ff483848540)
... which I can not get rid of.
If anyone could help me, I'd be really happy,
Help me please.