xorg.conf

xorg.conf
Name	xorg.conf
Developer	X.Org Foundation
Released	1990s
Latest release	varies with X.Org Server
Operating system	Linux (kernel), FreeBSD, NetBSD, OpenBSD
Genre	configuration file

xorg.conf is the legacy primary configuration file historically used by the X.Org Server and its predecessors to configure display hardware, input devices, and driver options for graphical sessions on systems such as Debian, Ubuntu, Fedora, Arch Linux, Red Hat Enterprise Linux and BSD variants. It served as a static declarative mapping between the X Window System server and peripherals like ATI/Radeon, NVIDIA and Intel graphics, and input devices from vendors such as Logitech and Wacom. Over time, dynamic autodetection via udev, HAL, and kernel mode-setting reduced the need for manual configuration, but xorg.conf remains a powerful tool for specialized setups, legacy hardware, and troubleshooting in environments including GNOME, KDE, Xfce and window managers like i3.

History

xorg.conf originated in the era of XFree86 and the original X Window System implementations where manual configuration was necessary for heterogeneous hardware in distributions like Slackware and Red Hat Linux. With the formation of the X.Org Foundation and the move toward Linux (kernel) kernel mode-setting and user-space device management via udev and DeviceKit, the reliance on xorg.conf declined. Major projects and distributions—Debian, Ubuntu, Fedora, SUSE Linux Enterprise Server, and BSD projects—shifted toward automatic configuration, while vendors such as NVIDIA Corporation and AMD provided proprietary drivers that still generated or advised xorg.conf fragments. Efforts by maintainers and contributors from projects like X.Org Server and Mesa influenced the file's semantics and the introduction of mechanisms for per-seat and per-device configuration.

Purpose and function

xorg.conf provides explicit control over mapping between the X.Org Server and hardware components such as PCI Express, GPUs from Intel, NVIDIA, and AMD/ATI, monitors with specific modelines, and input devices including keyboards and Wacom tablets. System administrators for environments like Ubuntu Server with Xfce, specialized workstations used in Blender or scientific visualization with Mesa backends, and legacy hardware in projects such as Debian derivatives use xorg.conf to enforce modes, disable hotplugging, configure multiple GPUs for Xinerama or RandR, and set driver-specific options from vendors including NVIDIA Corporation and Intel. It also interfaces with display managers such as LightDM, GDM, and SDDM to ensure consistent session startup.

File format and syntax

The file uses a plain-text stanza syntax with named sections such as ServerLayout, Device, Monitor, Screen, InputDevice, and Files. Each stanza uses identifiers and keyword/value pairs similar to configuration styles found in software from projects like MIT’s X Consortium heritage. Sections are delimited and nested with braces and recognize directives for options accepted by drivers including the nouveau driver, xf86-video-intel, and proprietary NVIDIA Corporation modules. For advanced options administrators reference driver-specific documentation maintained by entities like X.Org Foundation, Mesa, and vendor manuals from NVIDIA Corporation and AMD. Syntax errors may prevent the X.Org Server from starting and are diagnosed via server logs such as Xorg.0.log produced at boot or display-manager startup.

Common sections and options

Common sections include: - ServerLayout: arranges Screen, InputDevice references and links to display managers such as LightDM and GDM. - Device: selects a driver (e.g., xf86-video-ati, xf86-video-nouveau, nvidia) and options like BusID for PCI Express enumeration and driver-specific flags provided by NVIDIA Corporation or Intel. - Monitor: contains Modeline entries and Option directives used for EDID overrides when interacting with monitors from manufacturers such as Dell, LG, and Samsung. - Screen: binds Device and Monitor and configures depths and visual types for compositors like Compton or xcompmgr used in Xfce or Openbox sessions. - InputDevice: configures keyboards and mice, touchpads (e.g., Synaptics), and tablets (e.g., Wacom).

Options commonly tweaked include IgnoreEDID, HorizSync/VertRefresh modelines, Option "AccelMethod" for acceleration choices provided by drivers like nouveau or nvidia, and Option "DRI" settings aligning with Mesa and kernel DRM subsystems.

Generation and tools

Tools that generate or assist with xorg.conf include Xorg’s built-in --configure mode, the xorg.conf.d directory and snippet approach adopted by Debian, Arch Linux, and Fedora, and vendor utilities from NVIDIA Corporation that write xorg.conf sections. Distributions provide helpers and packaged snippets managed by projects such as systemd seat management and udev rules authored by freedesktop.org contributors. Utilities like X -configure, nvidia-xconfig, and distribution-specific tools in Ubuntu and openSUSE automate creation; sysadmins often use text editors common on systems like vim or emacs to craft or edit files manually.

Troubleshooting and customization

When the X.Org Server fails to start, administrators inspect Xorg.0.log and systemd journal entries to trace issues involving drivers from NVIDIA Corporation, Intel, or AMD and conflicts with kernel mode-setting. Common troubleshooting steps include creating minimal Device/Monitor/Screen stanzas, disabling conflicting modules such as nouveau when using proprietary NVIDIA Corporation drivers, or splitting configuration into /etc/X11/xorg.conf.d snippets used by distributions like Arch Linux and Debian. Customization tasks include forcing modelines for legacy displays from manufacturers like Sony or Philips, enabling multi-seat setups in enterprise environments using Red Hat Enterprise Linux or SUSE Linux Enterprise Server, and tuning acceleration and compositing behavior for desktop environments such as GNOME and KDE.

Category:X Window System configuration files