Linux Known Issues

Presently known issues with UE4 natively running in Linux. A page of bugs until we have a better solution for tracking. This page is part of the Linux Support area. ***

If you get an error like this:

UnrealBuildTool Exception: System.Security.SecurityException: No access to the given key ---> System.UnauthorizedAccessException: Access to the path "/etc/mono/registry" is denied.

you need to:

$ export MONO_REGISTRY_PATH=~/.mono/registry

otherwise you can create the default registry path with:

$ sudo mkdir -p /etc/mono/registry/LocalMachine

If you get a following error:

Localisation.Automation.cs(156,96): error CS0234: The type or namespace name `LocaleCodeHelper' does not exist in the namespace `OneSky'. Are you missing an assembly reference?

from your engine root folder do:

$ cd Engine/Source/ThirdParty/OneSky
$ xbuild OneSky.csproj /verbosity:quiet /nologo /p:TargetFrameworkVersion=v4.0 /p:Configuration="Release"
$ cd -
$ cp Engine/Source/ThirdParty/OneSky/bin/Release/OneSky.dll Engine/Binaries/DotNET/OneSky.dll



- No known issues





- Arch Linux users get a shader compile crash when starting cooked demos from the Wiki,

- Surround display setup (2+ screens) does not work properly/at all with NVIDIA, -- FIXED in 4.5. If you are rebuilding SDL yourself, make sure you have Xinerama/XRandR headers/libs installed.



- Arch Linux users are experiencing linker errors at related to libSDL2 and libdl not being linked in, causing a build failure. This happens with both Clang-3.3 and Clang-3.4


- Building Textures takes an awful long time compared to Windows,

- ShaderCompileWorkers turn into zombies when they complete converting the shader (FIXED by amigo), -- Actually was fixed by rewriting shader compile manager to use proper platform abstraction

- Some Linux users (tested on Ubuntu 14.04) are unable to use the file browser dialog,

- Note that some people have experienced a problem with the Editor not displaying anything in the Content Browser. One work-around is opening the Unreal Project from a case insensitive filesystem, such as a mounted fat volume on your system.

- If you are getting a washed off look using Nvidia binary driver, try setting __GL_FRAMEBUFFER_BLIT_IGNORE_SRGB=1 as an ENV variable before launching the Editor.

- Opening and compiling existing C++ projects does not work (now works through Project Browser Convert-In-Place option, preliminary FIXED by amigo),

- Opening and compiling existing C++ projects using other options (Copy Convert, etc) or loading them from the command line still broken due to a missing dialog (SDL2 popup dialog implemented by amigo),

- Creating from templates, or using existing C++ projects - other outstanding issues ie. missing IDE error, missing IDE plugins, etc,

- Arch Linux users are unable to start the editor in normal POSIX multi-threaded mode, but only using a -onethread command line argument. Try installing pthreads via pecl install pthreads (thanks to IRC user fuken for the tip) or, building the editor using a Debug profile: make UE4Editor-Linux-Debug instead.

- Lightmass crashes/lightbuilding fails (FIXED by amigo) still experiencing in russian (ru_RU) locale,

- Some dialogs ocassionaly show up black/no contents visible (FIXED by whammy),

- Cooking crashes because wrong Shader Platform (GRHIShaderPlatform) is being selected (SP_PCD3D_SM5 instead of SP_OPENGL_SM4 or SP_OPENGL_SM5) (FIXED by amigo),

- Cooking reports failure in the notification dialog, even though it completes successfully,

- Cooking does not produce a needed Engine/GlobalShaders-GLSL_150.bin and Engine/GlobalShaders-GLSL_430.bin files (FIXED by amigo),

- Moving objects using the left mouse button through the gizmo doesn't work; rotating and scaling does (FIXED by whammy),

- File and Font dialogs need improvements/re-implementation - ideally we need a pure Slate implementation,

- Baking lighting fails arbitrarily, or works on some projects - inconsistent,

- Optimus based laptop users who are getting Assert failed: IsInRenderingThread() or DRI buffer related errors should try running editor with: PRIMUS_SYNC=1 primusrun UE4Editor (thanks to HicksD for this tip),

- When running with the -opengl4 flag, the 3D viewports will appear entirely black. Workaround is to turn anti-aliasing in scalability settings (Settings->Scalability) to medium or lower.

- openSUSE users may need to run the editor with : cd Engine/Binaries/Linux && LD_LIBRARY_PATH=":$LD_LIBRARY_PATH:../ThirdParty/LinuxNativeDialogs/Linux/x86_64-unknown-linux-gnu/:" to avoid getting messages about missing libs.

- Gentoo users might need to run the editor with: cd Engine/Binaries/Linux && LD_LIBRARY_PATH=. ./UE4Editor to avoid getting messages about missing libs. As of 4.8 this is no longer necessary for OpenSUSE users.

- sometimes alt+tab does not appear ontop of everything, instead it is behind all windows.

- right mouse button gets stuck sometimes so that it does not aim anymore but it dollies in and out

- opening widget reflector, and dragging its window doubles total slate tick time.

- dragging any window (non-ue4) over the editor window also increases total slate tick time.

- opening a window (ie. char. BP) on the 2nd screen triples/quadruples total slate tick time.

- opening a window (ie. mat.ed) on the 2nd screen only doubles or less total slate tick time.

- dragging mouse over the details panel widgets triples or more the total slate tick time.

- content browser does not allow some keyboard events (ie. F2 to rename).

- Font/text on UI showing up as rectangles can be addressed by

- For artifacts on Mesa driver, try updating to latest. More info at

- Sometimes attempting to copy & paste or duplicate blueprint nodes stops working (WORKAROUND: copy & paste anything in another window, such as a text editor, and the editor should be able to copy & paste / duplicate blueprint nodes once more).

C++ projects and IDE's

- *NOTE* As of 4.8 with the NullSourceCodeAccessor this is no longer an issue but this is still some helpfull information if you want to use another SourceCodeAccessor.

- Unable to create C++ template based projects because "an IDE is not installed". Install kdevelop or or use the alternative code accessors below by adding them to Engine/Config/Linux/LinuxEngine.ini

- To use a specific IDE SourceCodeAccessor add one of the following lines to Engine/Config/Linux/LinuxEngine.ini










Note you have to install an IDE plugin:

- For Qt Creator:

- For VIM or EMACS:

- For Sublime Text:

- For KDevelop there is a plugin that comes with the engine source code that is aromatically built with UE4Editor.

- For Eclipse CDT: (also works for windows and mac) - Fork updated for new versions.

Clone the plugin to Engine/Plugins/Developer and then cd ../../../ && make UE4Editor

Is this still an issue?

   The project still breaks at a later point.

Loading C++ Project

- when loading up the project and there is no editor module for a c++ project it will compile the missing editor module for your project but then crash, the module is built but something else crashes afterwards.

- you can either

  1. start the editor and load the project then let it compile and crash then start the Editor and load the Project again.
  2. build the module in the IDE of choice then start the editor and load the project.
  3. build the module in the terminal, then start the editor and load the project.

- if it has to build the module again it may crash at the same spot.



- hlslcc leaks memory like a faucet (FIXED by nsf),

- file communication process really needs improvements (or be abandoned in favour of using FIFOs or Messaging/UdpMessaging?) (FIXED by Epic|rcl)


- Platform and process integration needs implementation/testing


No known issues


No known issues

SDL2 issues

4.8 branch

All the window issues mentioned below ( Official <= 4.7 branch ) are fixed.

- Double click on Titlebar area doesn't maximize/restore the window. (Fixed by yaakuro)

- Sometimes the Tooltip window does not disappear. (Happens when another thread starts for example if the Import File Dialog apears the open Tooltip will stuck)

- Notification window is ontop of some dialog boxes. (Fixed by yaakuro)

- Infinite rotation/scaling of objects in the viewport not possible.

- In Content Browser renaming and deleting does not work.

- Sometimes after creating new item in the content browser, renaming does not work because focus is not set back. Workaround is right click on the object you like to rename and choose rename :D. (Fixed by yaakuro)

Official <= 4.7 branch

- In some cases a Pre-click of a window is neccessary. To get proper mouse menu/click behavior after chaning a window a pre-click is neccesary. ( > 4.7 branch) (Fixed by yaakuro)

- Tooltips and Popup Menus visible in Pagers and over Unity hud ( > 4.7 branch ) (Fixed by yaakuro)

- Cannot order windows and window focus, - dragging and dropping from one window to another, ie. Asset Browser to Blue Print is impossible, as BP window does not stay on-top, -- Fixed by yaakuro and should work ( >= 4.7 branch)

- Cannot send keyboard and mouse focus without changing window stacking, - -- Example of a broken behavior? -- Fixed by yaakuro and should work ( > 4.7 branch)

- Cannot prevent windows like popups from appearing in task bar, -- SDL bundled with the engine has been extended to allow this (additional window creation flag)

- Cannot generate "inactive" or "focus transparent" windows, -- This can be added, but what do we need it for? Tooltips are fine being utility windows (and ability to click them is actually useful as they can have hyperlinks) (Fixed by Yaakuro)

- Does not support opacity, -- SDL bundled with the engine has been extended to support this (on X11).

- Cannot block window selection, -- Example of a broken behavior? ( > 4.7 branch possible)

- Need to be able to enumerate all graphics adapters in the system and get their basic parameters (brand, name, VRAM size...) -- SDL does support Xinerama and XRandR, i.e. all the facilities that X11 provides in that regard.

- Need to be able to create a simple text window for console output, without needing to render text in advance,

Command Line Staging/Cooking

- At this moment staging in the terminal is broke, it may also break in editor. parameters sent to UBT from Automation tool are being wrongly ordered and causing the cook/stage/build/archive to fail.

Performance Troubleshooting

As per Epic|rcl:

$ sudo perf record -a -g sleep 60

Smaller intervals than 60 sec can be used as well..

$ perf report --sort comm,dso,sym

Then identify the offender and complain....use Dev builds, of course.

Getting GLSL shaders source

1 Uncomment r.DumpShaderDebugInfo=1 in ConsoleVariables.ini
2 Tweak GUID (change a random digit init) in ShaderVersion.usf
3 Launch the editor

.desktop file template

Please change the location of the UnrealEngine directory:

[Desktop Entry]
Exec=Documents/UnrealEngine/Engine/Binaries/Linux/UE4Editor -opengl4
Name=Unreal Engine Editor

Window Managers

Xfce 4.10+

Switch on the composite manager (Settings/Window Manager Tweaks/Compositor)


UE4Editor does not need any special setting in the default version of Unity WM.



Problems with tooltips (framerate drop and smearing) can be avoided by disabling "Allow applications to block compositing" in the KDE Compositor settings.

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