Section: User Commands (1)Updated: xorg-server 22.214.171.1242Local indexUp
Xdmx - Distributed Multi-head X server
[:display] [option ...]
is a proxy X server that uses one or more other X servers as its display
devices. It provides multi-head X functionality for displays that might
be located on different machines.
functions as a front-end X server that acts as a proxy to a set of
back-end X servers. All of the visible rendering is passed to the
back-end X servers. Clients connect to the
front-end, and everything appears as it would in a regular multi-head
configuration. If Xinerama is enabled (e.g., with
on the command line), the clients see a single large screen.
communicates to the back-end X servers using the standard X11 protocol,
and standard and/or commonly available X server extensions.
In addition to the normal X server options described in the
accepts the following command line switches:
This specifies the name(s) of the back-end X server display(s) to connect
to. This option may be specified multiple times to connect to more than
one back-end display. The first is used as screen 0, the second as screen 1,
etc. If this option is omitted, the
environment variable is used as the single back-end X server display.
This specifies the source to use for XInput extension devices. The
choices are the same as for
described below, except that core devices on backend servers cannot be
treated as XInput extension devices. (Although extension devices on
backend and console servers are supported as extension devices under
This specifies the source to use for the core input devices. The choices are:
A set of dummy core input drivers are used. These never generate any
The raw keyboard and pointer from the local computer are used. A
comma-separated list of driver names can be appended. For example, to
select the example Linux keyboard and PS/2 mouse driver use:
The following drivers have been implemented for Linux: kbd, ms (a
two-button Microsoft mouse driver), ps2 (a PS/2 mouse driver), usb-mou
(a USB mouse driver), usb-kbd (a USB keyboard driver), and usb-oth (a
USB non-keyboard, non-mouse driver). Additional drivers may be
implemented in the future. Appropriate defaults will be used if no
comma-separated list is provided.
If the display-name is a back-end server, then core input events are
taken from the server specified. Otherwise, a console window will be
opened on the specified display.
is followed by ",xi" then XInput extension devices on the display will
be used as
XInput extension devices. If the
is followed by ",noxi" then XInput extension devices on the display will
be used as
XInput extension devices. Currently, the default is ",xi".
is followed by ",console" and the
refers to a display that is used as a backend display, then a console
window will be opened on that display
that display will be treated as a backend display. Otherwise (or if
",noconsole" is used), the display will be treated purely as a backend
or a console display, as described above.
is followed by ",windows", then outlines of the windows on the backend
will be displayed inside the console window. Otherwise (or if
",nowindows" is used), the console window will not display the outlines
of backend windows. (This option only applies to console input.)
is followed by ",xkb", then the next 1 to 3 comma-separated parameters
will specify the keycodes, symbols, and geometry of the keyboard for
this input device. For example, ",xkb,xfree86,pc104" will specify that
the "xfree86" keycodes and the "pc104" symbols should be used to
initialize the keyboard. For an SGI keyboard, ",xkb,sgi/indy(pc102)"
might be useful. A list of keycodes, symbols, and geometries can be
If this option is not specified, the input device will be queried,
perhaps using the XKEYBOARD extension.
If this option isn't specified, the default input source is the first
back-end server (the one used for screen 0). The console window shows
the layout of the back-end display(s) and pointer movements and key
presses within the console window will be used as core input devices.
Several special function keys are active, depending on the input
will terminate the
server in all modes.
will toggle a
server grab in console mode (a special cursor, currently a spider, is
used to indicate an active server grab).
will toggle fine-grain motion in console mode (a special cursor,
currently a cross hair, is used to indicate this mode). If this mode is
combined with a server grab, then the cursor will have 4 lines instead
of only 2.
Ctrl-Alt-F1 through Ctrl-Alt-F12
will switch to another VC in local (raw) mode.
This option turns on (legacy) support for the shadow frame buffer.
This option turns off (legacy) support for the shadow frame buffer.
Note that this option has been deprecated and will be removed in the
This option turns off support for displaying multiple cursors on
overlapped back-end displays. This option is available for testing and
This option sets the
server's default font path. This option can be specified multiple times
to accommodate multiple font paths. See the
section below for very important information regarding setting the
default font path.
Specify the configuration file that should be read. Note that if the
command-line option is used, then the configuration file will be
Specify a configuration to use. The
will be the name following the
keyword in the configuration file.
-stat interval screens
This option enables the display of performance statistics. The interval
is in seconds. The screens is a count of the number of back-end screens
for which data is printed each interval. Specifying 0 for screens will
display data for all screens.
For each screen, the following information is printed: the screen
number, an absolute count of the number of XSync() calls made
(SyncCount), the rate of these calls during the previous interval
(Sync/s), the average round-trip time (in microseconds) of the last 10
XSync() calls (avSync), the maximum round-trip time (in microseconds) of
the last 10 XSync calls (mxSync), the average number of XSync() requests
that were pending but not yet processed for each of the last 10
processed XSync() calls, the maximum number of XSync() requests that
were pending but not yet processed for each of the last 10 processed
XSync() calls, and a histogram showing the distribution of the times of
all of the XSync() calls that were made during the previous interval.
(The length of the moving average and the number and value of histogram
bins are configurable at compile time in the
This option sets the
in milliseconds for XSync() batching. An
less than or equal to 0 will disable XSync() batching. The default
is 100 ms.
This option disables the offscreen optimization. Since the lazy window
creation optimization requires the offscreen optimization to be enabled,
this option will also disable the lazy window creation optimization.
This option disables the lazy window creation optimization.
This option disables the primitive subdivision optimization.
Disable use of the XKB extension for communication with the back end
displays. (Combine with
to disable all use of XKB.)
This option sets the root window's default depth. When choosing a
default visual from those available on the back-end X server, the first
visual with that matches the depth specified is used.
This option can be combined with the
option, which specifies the default color visual class, to force the use
of a specific depth and color class for the root window.
This option disables the RENDER extension.
This option disables GLX proxy -- the build-in GLX extension
implementation that is DMX aware.
This option disables the swap group and swap barrier extensions in GLX
This option enables synchronization after a swap buffers call by waiting
until all X protocol has been processed. When a client issues a
glXSwapBuffers request, Xdmx relays that request to each back-end X
server, and those requests are buffered along with all other protocol
requests. However, in systems that have large network buffers, this
buffering can lead to the set of back-end X servers handling the swap
buffers request asynchronously. With this option, an XSync() request is
issued to each back-end X server after sending the swap buffers request.
The XSync() requests will flush all buffered protocol (including the
swap buffers requests) and wait until the back-end X servers have
processed those requests before continuing. This option does not wait
until all GL commands have been processed so there might be previously
issued commands that are still being processed in the GL pipe when the
XSync() request returns. See the
option below if Xdmx should wait until the GL commands have been
This option enables synchronization after a swap buffers call by waiting
until all GL commands have been completed. It is similar to the
option above; however, instead of issuing an XSync(), it issues a
glFinish() request to each back-end X server after sending the swap
buffers requests. The glFinish() request will flush all buffered
protocol requests, process both X and GL requests, and wait until all
previously called GL commands are complete before returning.
This option ignores font paths that are not available on all back-end
servers by removing the bad font path(s) from the default font path
list. If no valid font paths are left after removing the bad paths, an
error to that effect is printed in the log.
This option enables the dynamic addition and removal of screens, which
is disabled by default. Note that GLXProxy and Render do not yet
support dynamic addition and removal of screens, and must be disabled
command line options described above.
This option specifies parameters on the command line. Currently, only
parameters dealing with XKEYBOARD configuration are supported. These
parameters apply only to the core keyboard. Parameter values are
installation-dependent. Please see
or a similar directory for complete information.
Defaults to "xfree86". Other values may include "sgi" and "sun".
Defaults to "pc101". When used with "xfree86" rules, other values may
include "pc102", "pc104", "pc105", "microsoft", and many others. When
used with "sun" rules, other values may include "type4" and "type5".
Defaults to "us". Other country codes and "dvorak" are usually
Defaults to "".
Defaults to "".
CONFIGURATION FILE GRAMMAR
The following words and tokens are reserved:
Comments start with a
mark and extend to the end of the line. They may appear anywhere. If a
configuration file is read into
the comments in that file will be preserved, but will not be editable.
The name following
is used as an identifier for the configuration, and may be passed to
command line option. The name of a display should be standard X display
name, although no checking is performed (e.g., "machine:0").
For names, double quotes are optional unless the name is reserved or
The first dimension following
is the dimension for tiling (e.g., 2x4 or 4x4). The second dimension
is the dimension of each display in the wall (e.g., 1280x1024).
The first geometry following
is the geometry of the screen window on the backend server. The second
geometry, which is always preceeded by a slash, is the geometry of the
root window. By default, the root window has the same geometry as the
line can be used to specify any command-line options (e.g.,
(It cannot be used to specify the name of the front-end display.) The
option line is processed once at server startup, just line command line
options. This behavior may be unexpected.
CONFIGURATION FILE EXAMPLES
Two displays being used for a desktop may be specified in any of the
The font path used by the
front-end server will be propagated to each back-end server,which
requires that each back-end server have access to the exact same font
paths as the front-end server. This can be most easily handled by
either using a font server (e.g., xfs) or by remotely mounting the font
paths on each back-end server, and then setting the
server's default font path with the
command line option described above.
For example, if you specify a font path with the following command line:
will initialize the front-end
server and each of the back-end servers to use the font server on d0.
Some fonts might not be supported by either the front-end or the
back-end servers. For example, let's assume the front-end
server includes support Type1 fonts, but one of the back-end servers
does not. Let's also assume that the default font path for
includes Type1 fonts in its font path. Then, when
initializes the default font path to load the default font, the font
path that includes Type1 fonts (along with the other default font paths
that are used by the
server) is sent to the back-end server that cannot handle Type1 fonts.
That back-end server then rejects the font path and sends an error back
then prints an error message and exits because it failed to set the
default font path and was unable load the default font.
To fix this error, the offending font path must be removed from the
default font path by using a different
command line option.
option can also be added to the configuration file as described above.
The back-end machines are d0 and d1, core input is from the pointer and
keyboard attached to d0, clients will refer to :1 when opening windows:
Note that local input can be used under Linux while another X session is
running on :0 (assuming the user can access the Linux console tty and
mouse devices): a new (blank) VC will be used for keyboard input on the
local machine and the Ctrl-Alt-F* sequence will be available to change
to another VC (possibly back to another X session running on the local
machine). Using Ctrl-Alt-Backspace on the blank VC will terminate the
Xdmx session and return to the original VC.
This example uses the configuration file shown in the previous section:
The USB device drivers use the devices called
/dev/input/event0, /dev/input/event1, etc.
under Linux. These devices are driven using the
Linux kernel module, which is part of the hid suite. Please note that
if you load the
Linux kernel modules, then USB devices will appear as core Linux input
devices and you will not be able to select between using the device only
core device or an
XInput extension device. Further, you may be unable to unload the
Linux kernel module if
is configured to use
as an input device (this is quite helpful for laptop users and is set up
by default under some Linux distributions, but should be changed if USB
devices are to be used with
The USB device drivers search through the Linux devices for the first
mouse, keyboard, or non-mouse-non-keyboard Linux device and use that
was invoked with
compiled to use the XKEYBOARD extension, then a keyboard on a backend or
console will be initialized using the map that the host X server
If the XKEYBOARD extension is used for both
and the host X server for the keyboard (i.e., the backend or console X
server), then the type of the keyboard will
be obtained from the host X server and the keyboard under
will be initialized with that information. Otherwise, the default type
of keyboard will be initialized. In both cases, the map from the host X
be used. This means that different initial behavior may be noted with
and without XKEYBOARD. Consistent and expected results will be obtained
by running XKEYBOARD on all servers and by avoiding the use of
on the backend or console X servers prior to starting
is specified on the
command line, then that map will currently be used for all keyboards.
MULTIPLE CORE KEYBOARDS
X was not designed to support multiple core keyboards. However,
provides some support for multiple core keyboards. Best results will be
obtained if all of the keyboards are of the same type and are using the
same keyboard map. Because the X server passes raw key code information
to the X client, key symbols for keyboards with different key maps would
be different if the key code for each keyboard was sent without
translation to the client. Therefore,
will attempt to translate the key code from a core keyboard to the key
code for the key with the same key symbol of the
core keyboard that was loaded. If the key symbol appears in both maps,
the results will be expected. Otherwise, the second core keyboard will
return a NoSymbol key symbol for some keys that would have been
translated if it was the first core keyboard.