Virtual Network Computing Xvnc(1)
NAME
Xvnc - the X VNC server
SYNOPSIS
/usr/bin/Xvnc [options] :display#
DESCRIPTION
Xvnc is the X VNC (Virtual Network Computing) server. It is
based on a standard X server, but it has a "virtual" screenrather than a physical one. X applications display them-
selves on it as if it were a normal X display, but they canonly be accessed via a VNC viewer - see vncviewer(1).
So Xvnc is really two servers in one. To the applications it
is an X server, and to the remote VNC users it is a VNC server. By convention we have arranged that the VNC server display number will be the same as the X server display number, which means you can use eg. snoopy:2 to refer to display 2 on machine "snoopy" in both the X world and the VNC world.The best way of starting Xvnc is via the vncserver script.
This sets up the environment appropriately and runs some X applications to get you going. See the manual page for vncserver(1) for more information. OPTIONSXvnc takes lots of options - running Xvnc -help gives a
list. Many of these are standard X server options, which are described in the Xserver(1) manual page. In addition tooptions which can only be set via the command-line, there
are also "parameters" which can be set both via thecommand-line and through the vncconfig(1) program.
-geometry widthxheight
Specify the size of the desktop to be created. Default is 1024x768.-depth depth
Specify the pixel depth in bits of the desktop to be created. Default is 24, other possible values are 8,15, and 16 - anything else is likely to cause strange
behaviour by applications.-pixelformat format
Specify pixel format for server to use (BGRnnn or RGBnnn). The default for depth 8 is BGR233 (meaning the most significant two bits represent blue, the next TigerVNC Last change: 17 Apr 2006 1Virtual Network Computing Xvnc(1)
three green, and the least significant three represent red), the default for depth 16 is RGB565 and for depth 24 is RGB888.-cc 3
As an alternative to the default TrueColor visual, thisallows you to run an Xvnc server with a PseudoColor
visual (i.e. one which uses a color map or palette), which can be useful for running some old X applications which only work on such a display. Values other than 3(PseudoColor) and 4 (TrueColor) for the -cc option may
result in strange behaviour, and PseudoColor desktopsmust be 8 bits deep (i.e. -depth 8).
-inetd
This significantly changes Xvnc's behaviour so that it
can be launched from inetd. See the section below on usage with inetd.-help
List all the options and parametersPARAMETERS
VNC parameters can be set both via the command-line and
through the vncconfig(1) program.Parameters can be turned on with -param or off with
-param=0. Parameters which take a value can be specified as
-param value. Other valid forms are param=value
-param=value --param=value. Parameter names are case-
insensitive.-desktop desktop-name
Each desktop has a name which may be displayed by the viewer. It defaults to "x11".-rfbport port
Specifies the TCP port on which Xvnc listens for con-
nections from viewers (the protocol used in VNC iscalled RFB - "remote framebuffer"). The default is
5900 plus the display number.-rfbwait time, -ClientWaitTimeMillis time
Time in milliseconds to wait for a viewer which is TigerVNC Last change: 17 Apr 2006 2Virtual Network Computing Xvnc(1)
blocking Xvnc. This is necessary because Xvnc is
single-threaded and sometimes blocks until the viewer
has finished sending or receiving a message - note that
this does not mean an update will be aborted after this time. Default is 20000 (20 seconds).-httpd directory
Run a mini-HTTP server which serves files from the
given directory. Normally the directory will contain the classes for the Java viewer. In addition, files with a .vnc extension will have certain substitutions made so that a single installation of the Java VNCviewer can be served by separate instances of Xvnc.
-httpPort port
Specifies the port on which the mini-HTTP server runs.
Default is 5800 plus the display number.-rfbauth passwd-file, -PasswordFile passwd-file
Specifies the file containing the password used to authenticate viewers. The file is accessed each time a connection comes in, so it can be changed on the fly via vncpasswd(1).-deferUpdate time
Xvnc uses a "deferred update" mechanism which enhances
performance in many cases. After any change to theframebuffer, Xvnc waits for this number of milliseconds
(default 1) before sending an update to any waiting clients. This means that more changes tend to get coalesced together in a single update. Setting it to 0 results in the same behaviour as earlier versions ofXvnc, where the first change to the framebuffer causes
an immediate update to any waiting clients.-SendCutText
Send clipboard changes to clients (default is on). Note that you must also run vncconfig(1) to get the clipboard to work.-AcceptCutText
Accept clipboard updates from clients (default is on). Note that you must also run vncconfig(1) to get the clipboard to work. TigerVNC Last change: 17 Apr 2006 3Virtual Network Computing Xvnc(1)
-AcceptPointerEvents
Accept pointer press and release events from clients (default is on).-AcceptKeyEvents
Accept key press and release events from clients (default is on).-DisconnectClients
Disconnect existing clients if an incoming connectionis non-shared (default is on). If DisconnectClients is
false, then a new non-shared connection will be refused
while there is a client active. When combined with NeverShared this means only one client is allowed at a time.-NeverShared
Never treat incoming connections as shared, regardlessof the client-specified setting (default is off).
-AlwaysShared
Always treat incoming connections as shared, regardlessof the client-specified setting (default is off).
-Protocol3.3
Always use protocol version 3.3 for backwards compati-
bility with badly-behaved clients (default is off).
-CompareFB
Perform pixel comparison on framebuffer to reduce unnecessary updates (default is on).-SecurityTypes sec-types
Specify which security schemes to use separated by com-
mas. At present only "None" and "VncAuth" are sup-
ported. The default is "VncAuth" - note that if you
want a server which does not require a password, you must set this parameter to "None".-IdleTimeout seconds
The number of seconds after which an idle VNC connec-
tion will be dropped (default is 0, which means that idle connections will never be dropped). TigerVNC Last change: 17 Apr 2006 4Virtual Network Computing Xvnc(1)
-QueryConnect
Prompts the user of the desktop to explicitly accept or reject incoming connections. This is most useful when using the vnc.so module or x0vncserver(1) program to access an existing X desktop via VNC. The vncconfig(1) program must be running on the desktop in order for QueryConnect to be supported by thevnc.so(1) module or Xvnc(1) program. The
x0vncserver(1) program does not require vncconfig(1) to be running.-localhost
Only allow connections from the same machine. Useful ifyou use SSH and want to stop non-SSH connections from
any other hosts. See the guide to using VNC with SSH on the web site.-log logname:dest:level
Configures the debug log settings. dest can currently be stderr or stdout, and level is between 0 and 100, 100 meaning most verbose output. logname is usually * meaning all, but you can target a specific source file if you know the name of its "LogWriter". Default is *:stderr:30.-RemapKeys mapping
Sets up a keyboard mapping. mapping is a comma-
separated string of character mappings, each of theform char->char, or char<>char, where char is a hexade-
cimal keysym. For example, to exchange the " and @ sym-
bols you would specify the following: RemapKeys=0x22<>0x40USAGE WITH INETD
By configuring the inetd(1M) service appropriately, Xvnc can
be launched on demand when a connection comes in, ratherthan having to be started manually. When given the -inetd
option, instead of listening for TCP connections on a given port it uses its standard input and standard output. There are two modes controlled by the wait/nowait entry in the inetd.conf file.In the nowait mode, Xvnc uses its standard input and output
directly as the connection to a viewer. It never has a listening socket, so cannot accept further connections from viewers (it can however connect out to listening viewers by TigerVNC Last change: 17 Apr 2006 5Virtual Network Computing Xvnc(1)
use of the vncconfig program). Further viewer connectionsto the same TCP port result in inetd spawning off a new Xvnc
to deal with each connection. When the connection to theviewer dies, the Xvnc and any associated X clients die.
This behaviour is most useful when combined with the XDMCPoptions -query and -once.
The provided application/x11/xvnc-inetd service defaults to
running/usr/bin/Xvnc -inetd -query localhost -once
securitytypes=none in nowait mode. This service can be enabled via svcadm(1m), and configured to use other modes or arguments via svccfg(1m). In this configuration, connecting to :0 will result in a newXvnc for that connection which should display the standard
graphical login screen on that machine. (To enable this, you will also have to enable XDMCP network connections on the login screen. See gdm(1) for details.) Because the user needs to login via this screen, it is usually OK to accept connections without a VNC password in this case. In the wait mode, when the first connection comes in, inetdgives the listening socket to Xvnc. This means that for a
given TCP port, there is only ever one Xvnc at a time.
Further viewer connections to the same port are accepted bythe same Xvnc in the normal way. Even when the original
connection is broken, the Xvnc will continue to run. If
this is used with the XDMCP options -query and -once, the
Xvnc and associated X clients will die when the user logs
out of the X session in the normal way. It is important to use a VNC password in this case. A typical command line to include in the service exec property might be:/usr/bin/Xvnc Xvnc -inetd -query localhost -once
passwordFile=/home/james/.vnc/passwd In fact typically, you would have one entry for each user who uses VNC regularly, each of whom has their own dedicated TCP port which they use. In this example, when user "james" connects, he enters his VNC password, then gets the login screen where he logs in in the normal way. However, unlike the previous example, if he disconnects, the session remainspersistent, and when he reconnects he will get the same ses-
sion back again. When he logs out of the X session, theXvnc will die, but of course a new one will be created
automatically the next time he connects. TigerVNC Last change: 17 Apr 2006 6Virtual Network Computing Xvnc(1)
SEE ALSO
vncconfig(1), vncpasswd(1), vncserver(1), vncviewer(1), Xserver(1), inetd(1) http://www.tigervnc.org AUTHOR Tristan Richardson, RealVNC Ltd. VNC was originally developed by the RealVNC team while at Olivetti Research Ltd / AT&T Laboratories Cambridge. TightVNC additions were implemented by Constantin Kaplinsky. Many other people participated in development, testing and support.ATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| Availability | x11/server/xvnc ||_____________________________|_____________________________|
| Interface Stability | Volatile ||_____________________________|_____________________________|
TigerVNC Last change: 17 Apr 2006 7