How to debug Xorg problems

Foreword

If you are experiencing a problem with Xorg, please see the common bugs document before filing a bug. Some easy configuration tweaks that fix a wide range of issues are listed there. If the problem you are seeing is not listed there or none of the workarounds seem to help, please consider filing a bug to help us make Fedora run better on your hardware.

Be prepared to include some information (logs) about your system as well. These should be complete (no snippets please), not in an archive, uncompressed, with MIME type set as text/plain.

Identifying your problem area

What driver am I using?

If you do not know already, try to find out what video driver you are using. Examine the file /var/log/Xorg.0.log. Quite early on, you will see some lines like this:

(II) VESA(0): initializing int10
(II) VESA(0): Bad V_BIOS checksum

The word in capital letters after (II) is the name of the driver in use (so, in this case, the word is VESA, indicating the vesa driver is in use). Drivers are packaged with the name xorg-x11-drv-(name), so the vesa driver is in the package xorg-x11-drv-vesa.

If you are using a driver with the name nvidia (not nv or nouveau) or fglrx, you are using a proprietary third-party video driver (respectively, the proprietary drivers provided by NVIDIA and AMD/ATI). Please do not report any bugs in these drivers to Fedora, as we do not provide or support these drivers. Report bugs either to the place where you got these drivers, or to NVIDIA or AMD.

What area might the problem be in?

• If the problem in question occurs when using 3D-accelerated applications - for instance, Blender, or 3D-accelerated games - the problem is a 3D acceleration issue, and you should include the information outlined in the appropriate section further down this page.

• Several drivers in Fedora use kernel mode setting (whereby the detection and selection of the output resolution and refresh rate is done in the kernel rather than the video card driver) by default. As of Fedora 12, these drivers are intel, radeon and nouveau. If you are using one of these drivers, test if the problem is related to kernel mode setting by disabling it: boot with the parameter nomodeset added to the kernel command line. If this affects the problem, it is a KMS-related issue, and you should include the information outlined in the appropriate section further down this page.

Information to include in your report

All bug reports

In all cases, the following should be attached to your bug report:

• All of the X server log file(s): /var/log/Xorg.*.log
• Your smolt profile. You can dump it to /tmp/smoltprofile.txt with the following command: smoltSendProfile -p > /tmp/smoltprofile.txt
• If you use a xorg.conf, please include it in the bug report, otherwise, please specify in the bug report that it does not exist. Usually this would be located at /etc/X11/xorg.conf, but see the xorg.conf manpage - man xorg.conf - for other standard locations.
• /var/log/Xorg.0.log from a trial run where you move your xorg.conf aside and let Xorg autodetect your hardware (if you have such a file).
• /var/log/dmesg especially in case of crashes and using KMS.
• content of /var/log/gdm/ only in cases there is nothing interesting in /var/log/Xorg.*.log and dmesg output

Rendering problems (unreadable text, corrupted display...)

As well as the information from the 'all bug reports' section, include the following information:

• A screenshot showing the problem if at all possible.

KMS-related issues

As well as the information from the 'all bug reports' section, include the following information:

• Boot with the parameter drm.debug=15 added to the kernel command line, reboot and attach /var/log/messages, /var/log/dmesg, and /var/log/Xorg.0.log to your bug report.
• Also, boot with the parameter nomodeset added to the kernel command line and attach /var/log/Xorg.0.log to your bug report.
• Explain how the behaviour differs when KMS is disabled, and whether both cases are problematic (but different), or whether the non-KMS case is what you consider to be the correct behavior.

3D acceleration issues

As well as the information from the 'all bug reports' section, include the following information:

• Output of the command glxinfo (if this is not installed, install the package glx-utils)
• A screenshot, if possible (if the system has crashed but the display on screen is something other than just blank, take a picture with a digital camera and attach that)
• Information as to whether or not other OpenGL applications are able to run without problems.

Creating a xorg.conf

If you need to make manual changes to X configuration, you will need to create a xorg.conf file if it doesn't already exist.

Input devices

Debugging of input devices is covered by a special wiki page.

Stack traces

You will need a stack trace if your X server crashes.

See the documentation on the upstream wiki.