Reviewing the Xorg.0.log

The Xorg.0.log shows the messages of the most recent start of the Xorg server, which provides graphics on most Linux systems. As such it is useful for debugging all sorts of graphics problems. Its messages can be cryptic to the uninitiated, so this article documents those messages that stumped me and what they mean. …

BACKGROUND
The Xorg.0.log can be read with less /var/log/Xorg.0.log. It's a good place to look when troubleshooting graphics problems. I also like to check it after installing a new distro or kernel, and after changing graphics configuration or hardware, even if everything seems to be normal.

The log is organized chronologically, newest entries last.

When reading the Xorg.0.log, be on the lookout for any lines beginning with (EE) which represent errors. Lines beginning with (WW) are advisories (Xorg melodramatically calls them "warnings") that can often be ignored but sometimes indicate a sub-optimal configuration or other issue. When in doubt, investigate and ask.

LOG ENTRIES I'VE LOOKED INTO

(II) v4l driver for Video4Linux
[snip]
(WW) Falling back to old probe method for v4l

This message was seen on a box running Mandriva 2010.2, kernel-desktop586-2.6.33.7-2mnb-1-1mnb2, cleanly installed, shortly after installation. Motherboard is an Intel DG31GL; graphics hardware is the onboard Intel G31 Express chipset. Xorg server is x11-server-xorg-1.7.7-1mdv2010.1 using module intel. The message was observed during a routine post-installation check of all logs.

As the webcam works properly without issue, and neither the man pages nor a web search turned up any useful information on this warning, chose to I ignore it.

(II) intel(0): direct rendering: DRI2 Enabled
(WW) intel(0): Option "PreferredMode" is not used

This message was seen on a box running Mandriva 2010.2, kernel-desktop586-2.6.33.7-2mnb-1-1mnb2, cleanly installed, shortly after installation. Motherboard is an Intel DG31GL; graphics hardware is the onboard Intel G31 Express chipset. Xorg server is x11-server-xorg-1.7.7-1mdv2010.1 using module intel. Resolution was set to 24 bit. The message was observed during a routine post-installation check of all logs; graphics appeared to be working properly without issue.

In man intel I read "The driver supports hardware accelerated 3D via the Direct Rendering Infrastructure (DRI), but only in depth 16…". Changing resolution from 24 to 16 bits and restarting the Xorg server eliminated the message.

REFERENCES
man xorg.conf, the man page for your display driver, and man pages for any other Xorg driver of interest. A list of display driver man pages appears at the end of the xorg.conf man page in the "see also" section. The man page for your display driver is particularly worth your while to read and will identify any all supported options and any limitations.

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About Warren Post

So far: Customer support guy, jungle guide, IT consultant, beach bum, entrepreneur, teacher, diplomat, over-enthusiastic cyclist. Tomorrow: who knows?
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One Response to Reviewing the Xorg.0.log

  1. Pingback: Security and stability tuning on Linux | A maze of twisty little passages

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