Cygwin/X Frequently Asked Questions

2026-03-26 20:35
     __________________________________________________________________

   Table of Contents
   Questions and Answers
   Bibliography
   Glossary
   A. GNU Free Documentation License

Questions and Answers

   1. General Information

        1.1. What is Cygwin/X?
        1.2. What is Cygwin?
        1.3. What is the X Window System?
        1.4. What is an X Server?
        1.5. What is an X client?
        1.6. What does DISPLAY=:0.0 mean?
        1.7. Why port the X Window System to Microsoft Windows?
        1.8. Is there a Cygwin/X newsgroup?
        1.9. Is there a Cygwin/X mailing list?

   2. Installation

        2.1. What versions of Windows does Cygwin/X run on?
        2.2. How is Cygwin/X installed?
        2.3. Fatal server error: Can't read lock file /tmp/.X0-lock
        2.4. Nothing appears to happen when I try to start the X server
                using the "XWin Server" start menu shortcut.

   3. Upgrade

        3.1. What happened to my X server? Where did /usr/X11R6/ go?
        3.2. I upgraded my X server and now I can't type anything into any
                X application

        3.3. I can't find startxwin.bat or startxwin.exe to start the X
                server

        3.4. Moved question
        3.5. My favourite font has gone! The font Emacs uses is just boxes
        3.6. Where has xhost/xlsfonts/etc. gone?
        3.7. How do I get rid of that menu at the top of my xterm?
        3.8. ssh -X now says "Warning: untrusted X11 forwarding setup
                failed: xauth key data not generated"

        3.9. nedit fails to start with an error message
        3.10. I start my X server with startx or xinit and now all my X
                windows are contained within one large root Windows
                window? How do I get it back to each X window in it's own
                Windows window?

        3.11. Moved question
        3.12. I upgraded and now X exits immediately after starting
        3.13. I upgraded and now X clients can't connect

   4. Configuration

        4.1. Is there an xorg.conf or XF86Config file?
        4.2. What are the command line options for X? How do I add command
                line options for X?

        4.3. Why does X ignore the display depth that I pass on the
                command line?

        4.4. I have a two button mouse, can I emulate a three button
                mouse?

        4.5. Is there a Focus-Follows-Mouse feature (Auto-Focus)?
        4.6. The option -nounixkill has no effect. How can i prevent the
                server shutdown an Ctrl-Alt-BackSpace?

        4.7. I have a multihead system. Do I need special options to make
                it work? I have a multihead system. Why are my
                X-application windows white?

        4.8. I have a firewall. Is there anything I have to take care of?

   5. Internationalization

        5.1. Keyboard support

              5.1.1. How do I use a non-U.S. keyboard layout?
              5.1.2. Is there a way to add a layout to the list of
                      autodetected layouts?

              5.1.3. Where can I find an xmodmap for my non-U.S. keyboard
                      layout?

              5.1.4. How do I get my non-U.S. keyboard modmap to be
                      installed when using xdmcp?

              5.1.5. Logging into AIX via XDMCP causes the keyboard to
                      function as if AltGr is permanently pressed.

              5.1.6. Loading an XKB keyboard layout selected with
                      -xkblayout fails

              5.1.7. I have Windows XP with Powertoys installed and AltGr
                      does not work. What can I do?

              5.1.8. AltGr does not work properly when connecting to
                      various older commercial unices (e.g. HP-UX, AIX) or
                      to old XFree86.

        5.2. Display problems

              5.2.1. How do I get bash to display accents and/or umlauts?
              5.2.2. How do I put bash into "8 bit" mode?
              5.2.3. How do I display unicode characters in an xterm?

   6. Remote connections

        6.1. X11Forwarding does not work with OpenSSH under Cygwin
        6.2. Why do remote programs crash with an X Error of failed
                request: BadAtom? Why do remote programs exit when you try
                to copy and paste?

        6.3. I'm confused about the difference between trusted and
                untrusted X11 forwarding. What does "Warning: untrusted
                X11 forwarding setup failed: xauth key data not generated"
                mean? Why is the SECURITY extension disabled?

        6.4. What does "Warning: no xauth data; using fake authentication
                data for X11 forwarding" mean?

        6.5. Why can't new remote X clients connect to the X server after
                20 minutes?

        6.6. Remote clients can't connect
        6.7. X sessions forwarded by PuTTY can't connect. Non-cygwin local
                X clients can't connect.

   7. XDMCP connections

        7.1. XDMCP fatal error: Session declined No valid address
        7.2. Why does Cygwin/X report AUDIT: client 1 rejected from IP
                remotehost?

        7.3. I get no login screen when using -query
        7.4. XDMCP does not work with Mandrake 8.1
        7.5. Why does GDM not work with -clipboard
        7.6. I get no login screen for Solaris
        7.7. XDMCP freezes with remote Solaris machine!
        7.8. Login to CDE on Solaris via XDMCP hangs Cygwin/X.
        7.9. Where can I find more information about XDMCP.

   8. Troubleshooting

        8.1. Cygwin/X failed with "Fatal Error". What does this mean?
        8.2. Is there a log file that I can look at for diagnostic
                information and error messages?

        8.3. I have a specific error message, what does it mean?
        8.4. I have a specific error message that is not addressed in the
                Error and Warning Messages section.

        8.5. My bug report the Cygwin/X mailing list was ignored. What do
                I do now?

        8.6. Why does Cygwin/X freeze right after startup?
        8.7. Cygwin/X has very poor performance. What's the reason?
        8.8. I have Microsoft Services for Unix installed and can't type
                anything. Help me!!!

        8.9. Cygwin/X is extremely slow, especially when using XDMCP to
                connect to remote machines.

        8.10. Simulated mouse wheel scrolling doesn't work with a
                TrackPoint mouse (found on IBM laptops) or Synaptics
                Touchpads

        8.11. Why is the root window not shown in normal mode?
        8.12. Why is the cross the default cursor in multiwindow mode?
        8.13. How can I adjust the linewidth in bash after resizing XTerm?
        8.14. Why do some menus not work if Num-Lock is on?

   9. Error and Warning Messages

        9.1. _XSERVTransmkdir: Owner of /tmp/.X11-unix should be set to
                root

        9.2. error opening security policy file
                /usr/X11R6/lib/X11/xserver/SecurityPolicy

        9.3. Duplicate invocation on display number: 0. Exiting.
        9.4. Fatal server error: could not open default font 'fixed'
        9.5. Could not init font path element /usr/share/fonts/*/,
                removing from list!

        9.6. The procedure entry point _check_for_executable could not be
                located

        9.7. cygX11-6.dll not found after installation or upgrade
        9.8. Exception: STATUS_ACCESS_VIOLATION
        9.9. Xlib: connection to "local_host_name_or_ip_address:0.0"
                refused by server Xlib: Maximum number of clients reached

        9.10. XIO: fatal IO error 104 (Connection reset by peer) on X
                server "127.0.0.1:0.0"

        9.11. Cannot Open Display: 127.0.0.1:0.0
        9.12. Out of environment space
        9.13. Too many parameters
        9.14. "xcb_xlib_lock: Assertion '!c->xlib.lock' failed." or
                "xcb_xlib_unlock: Assertion 'c->xlib.lock' failed."

        9.15. Fatal server error: Failed to activate core devices.
        9.16. "fatal error - unable to remap (some dll) to same address as
                parent: (some hex number) != (some other hex number)" or
                "(some dll): Loaded to different address: parent(some hex
                number) != child(some other hex number)"

        9.17. fork: child -1 - died waiting for longjmp before
                initialization, retry (some number), exit code (some hex
                number), errno (some other number)

   10. Porting Software

        10.1. Is there a list of software that has been ported to
                Cygwin/X?

        10.2. How do I start porting software to Cygwin/X?
        10.3. Are there common problems encountered when porting software
                to Cygwin/X?

        10.4. Problems building or linking OpenGL applications? Undefined
                reference to _glsomething?

   11. Contributing

        11.1. Are there step-by-step instructions for contributing to
                Cygwin/X?

        11.2. Are there editors for Windows that understand and preserve
                UNIX end of line characters?

        11.3. How should I generate patches for Cygwin/X?
        11.4. Where do I submit patches for Cygwin/X?
        11.5. Why doesn't the X Window System use GNU's autoconf?
        11.6. What compiler does Cygwin/X use, and which compilers are
                supported?

        11.7. Is cross-compiling from a non-Cygwin platform supported?
        11.8. Where can I get help for installing DocBook on Cygwin?

   12. Licenses, Patents, Trademarks, and Copyrights

        12.1. What licenses apply to Cygwin/X source code?
        12.2. What licenses apply to the X Window System source code?
        12.3. What license applies to Cygwin source code?
        12.4. Who holds the copyright on the Cygwin/X source code?
        12.5. Who holds the copyright on the X Window System source code?
        12.6. Who holds the copyright on the Cygwin source code?
        12.7. What license applies to Motif?
        12.8. Isn't "XWin" trademarked by StarNet Communications?

1. General Information

   1.1. What is Cygwin/X?

   Cygwin/X is a port of the X Window System to Cygwin. Cygwin provides a
   UNIX-like API on the Win32 platform.

   1.2. What is Cygwin?

   Cygwin tools are, in the words of the Cygwin FAQ, " ports of the
   popular GNU development tools and utilities for Microsoft Windows. They
   run thanks to the Cygwin library which provides the POSIX system calls
   and environment these programs expect. " Cygwin provides the compiler
   (gcc), libraries, headers, and other utilities which build and support
   the operation of Cygwin/X.

   1.3. What is the X Window System?

   [ScheiflerGettys92]

   The X Window System, or X, is a network-transparent window system. With
   X, multiple applications can run simultaneously in windows, generating
   text and graphics in monochrome or color on a bitmap display. Network
   transparency means that application programs can run on machines
   scattered through the network.

   1.4. What is an X Server?

   An X Server is a program that provides display and user input services
   to other programs. In comparison, a file server provides other programs
   with access to file storage devices. File servers are typically located
   in a remote location and you use the services of a file server from the
   machine that you are located at. In contrast, an X Server is typically
   running on the machine that you are located at; display and user input
   services may be requested by programs running on your machine, as well
   as by programs running on remote machines.

   1.5. What is an X client?

   An X client is a program that utilizes the display and user input
   services provided by an X Server. X clients may run on the same or
   disparate machine as the X Server that is providing display and user
   input services.

   1.6. What does DISPLAY=:0.0 mean?

   The DISPLAY environment variable instructs an X client which X server
   it is to connect to by default. Typically this can be overriden by
   running the client with a -display or -d command line option.

   The :0.0 part of the DISPLAY variable denote the display and the screen
   of an X server.

   The display is the first number and should equal the display number
   given to a running instance of an X server. By default the X server
   uses display number 0. If the X server is using TCP/IP for
   communication it listens on port 6000 + display-number for X client
   connections. For local (UNIX domain sockets) it uses the socket
   /tmp/.X11-unix/Xdisplay-number

   The screen denotes different output devices of the X server. You could
   start X with two -screen options and would end up with two X11 windows.
   Each of them is a different screen. Other X servers open different
   screens for different monitors connected to the computer.

   Cygwin/X supports different formats of the DISPLAY variable
     * :0.0 or unix:0.0
       This names a local X server and the communication uses the UNIX
       domain sockets.
     * hostname:0.0
       This names a remote X server and the communication uses the TCP/IP
       network.

   See the DISPLAY NAMES section of man X for more information.

   1.7. Why port the X Window System to Microsoft Windows?

   Porting X Window System to Microsoft Windows benefits many people and
   projects in many ways:
     * Prior to Cygwin/X only commercial, closed source X Servers were
       available for Microsoft Windows.
     * An X Server on Windows may be used to display the output of
       programs running on remote UNIX machines.
     * Cygwin/X, in conjunction with Cygwin, provides a complete
       compatibility layer for compiling and running UNIX applications on
       Microsoft Windows.

   1.8. Is there a Cygwin/X newsgroup?

   No, Cygwin/X does not have a newsgroup; however, we do have a mailing
   list. See Q: 1.9.

   You can read and post to the mailing list using your newsreader using
   the GMANE mail-to-news gateway.

   1.9. Is there a Cygwin/X mailing list?

   Yes, Cygwin/X is on-topic for the cygwin@cygwin.com mailing list.
   Non-subscribers may post to this list. Visit the Cygwin Mailing Lists
   page to subscribe to cygwin@cygwin.com as well as to read and search an
   online archive of the mailing list traffic.

2. Installation

   2.1. What versions of Windows does Cygwin/X run on?

   Cygwin/X aims to support all versions of Windows supported by Cygwin.

   However, Cygwin/X is not tested on older versions of Windows (i.e.
   Windows NT4, Windows 2000) and may be broken. Problem reports are
   welcomed.

   Cygwin/X requires Cygwin to compile and run. Cygwin is not, as of
   writing, available on Microsoft Windows CE, therefore Cygwin/X is not
   currently available on Microsoft Windows CE.

   2.2. How is Cygwin/X installed?

   The Cygwin/X User's Guide thoroughly documents the installation
   process. Installation is performed through Cygwin's setup program.

   2.3. Fatal server error: Can't read lock file /tmp/.X0-lock

   This question should be obsolete.

   A1: /tmp resides on a FAT filesystem

   Start the server with the -nolock option. See Q: 4.2.

   You should really consider updating the filesystem to NTFS using
   Microsoft's convert.exe tool.

   A2: /tmp resides on a NTFS filesystem.

   This can be caused by a stale lock file being left behind after the X
   server is run by a user with Adminstrator rights, which cannot be
   overwritten when the X server is next run by a user without
   Adminstrator rights.

   Failure to clean up the lock file properly is a bug in the X server,
   but until that is fixed the following workarounds may be neccessary.
    1. Try removing the stale lock file using rm -f /tmp/.Xn-lock where n
       is the display number. If this fails due to insufficent
       permissions, you must either get the owner or a user with
       Adminstrator rights to remove the stale lock file.
    2. Try starting the server with the -nolock option. (See Q: 4.2.)

   Technical details: The X server attempts to create a lock file in /tmp
   by creating the file under a temporary name, then renaming it to the
   proper name (by hard linking it under the correct name, then unlinking
   it from the temporary name). If this rename fails it attempts to read
   the existing lock file to determine the pid of an already running
   server. The FAT filesystem does not support hardlinks so this operation
   cannot succeed. On NFTS filesystems, the failure case appears to be
   that lock file was created successfully, but the rename failed due to a
   stale lock file created by a user with Adminstrator rights.

   2.4. Nothing appears to happen when I try to start the X server using
   the "XWin Server" start menu shortcut.

   A1:

   This answer should be obsolete.

   Task manager shows the startxwin.exe process starting, spawning
   XWin.exe and xterm.exe, but no windows are shown. Running startxwin.exe
   from a bash shell works correctly. This is caused by having tty in the
   CYGWIN environment variable set through the Windows control panel.
   Removing tty resolves this issue.

   If you really need CYGWIN=tty for working with cmd.exe windows, you'll
   have to arrange to set that by some other means before invoking
   cygwin.bat.

   A2:

   Try running startxwin from a bash shell in the mintty terminal
   emulator, it should output some error message which should indicate why
   it's not able to start.

     Note: For technical reasons, the output of XWin doesn't appear in
     cmd.exe windows unless the CYGWIN environment variable set through
     the Windows control panel contains tty, so to ensure the output can
     be seen, use mintty.

3. Upgrade

   3.1. What happened to my X server? Where did /usr/X11R6/ go?

   The upgrade from X.Org R6.8 to modular X.Org R7.4 made a lot of
   changes. Please read the announce email and pay attention to the
   upgrade instructions

   3.2. I upgraded my X server and now I can't type anything into any X
   application

   This question should be obsolete.

   Launch the X server via the shortcut under "Cygwin-X" on the start
   menu.

   Technical details: The startxwin.bat script used to set several
   enviroment variables used by the X server to specify the location of
   files it needs to access. Specifically this batch file would set
   XKEYSYMDB to /usr/X11R6/lib/X11/XKeysymDB. This file was moved to
   /usr/share/X11/XKeysymDB. The keyboard won't work if XKEYSYMDB points
   to a non-existent file.

   If you are (perhaps unintentionally) using a copy of the old
   startxwin.bat (perhaps under another name) to start the X server,
   remove the environment variables XAPPLRESDIR, XCMSDB, XNLSPATH and
   XKEYSYMDB from it, or (preferrably) use the updated startxwin.

   If echo $XKEYSYMDB outputs something, you have something else setting
   XKEYSYMDB in your environment. Find it and remove it.

   These variables were always being set to the defaults, so they can
   simply be removed. See Q: 8.8. for the reason why you might need to set
   them.

   3.3. I can't find startxwin.bat or startxwin.exe to start the X server

   The executable startxwin.exe previously used to start the X server has
   been retired and replaced with a shell script startxwin.

   The MS-DOS batch file startxwin.bat previously used to start the X
   server has been retired, as implementing this as a batch file made it
   difficult to reliably wait until the the X server had started before
   starting any clients.

   X.Org now uses the prefix /usr not /usr/X11R6. So startxwin.bat was
   moved from /usr/X11R6/bin/startxwin.bat to /usr/bin/startxwin.bat.

   A "XWin Server" shortcut to startxwin is created on the Start menu,
   under "Cygwin-X"

   startxwin and the Start menu link to it are now installed by the xinit
   package.

   3.4. Moved question

   3.5. My favourite font has gone! The font Emacs uses is just boxes

   Only minimal fonts will be installed after the upgrade from X.Org R6.8
   to modular X.Org.

   Font packages are now named font-<author/class>-<fonttype>

   Some packages dependencies have not yet been updated for the fonts they
   require, so you may need to manually install the needed fonts. For
   example, to provide the font emacs wants to use by default you will
   probably want to install font-adobe-dpi75 (or font-adobe-dpi100 if you
   like large fonts). This package provides the courier, helvetica, new
   century schoolbook and times font families.

   The lucida font family is provided by the package font-bh-dpi75 (or
   font-bh-dpi100). The monospaced version, lucida typewriter is provided
   by the package font-bh-lucidatypewriter-dpi75 (or
   font-bh-lucidatypewriter-dpi100).

   Note that after installing fonts you will need to restart the X server
   or run xset fp default; xset fp rehash to make the new fonts available

   3.6. Where has xhost/xlsfonts/etc. gone?

   Previously all the X utility programs were contained in a single
   package, xorg-x11-bin, which needed to be updated when any of the
   programs it contained was updated. In modular X each of these programs
   can be found in a separate package, usually named xhost/xlsfont/etc.

   3.7. How do I get rid of that menu at the top of my xterm?

   Run it as xterm +tb, or add XTerm*toolBar: false to ~/.Xresources

   3.8. ssh -X now says "Warning: untrusted X11 forwarding setup failed:
   xauth key data not generated"

   See Q: 6.1. and following. See point 3 in this mail. Use ssh -Y.

   Technical details: ssh tried to run xauth generate to create a
   untrusted cookie for the session, which failed because the server isn't
   compiled with the XCSECURITY extension built-in. Since OpenSSH 7.2p1,
   ssh does not fallback to trusted forwarding, so no X11 forwarding is
   setup.

   3.9. nedit fails to start with an error message

   This question should be obsolete.

$ nedit
X Error of failed request:  BadMatch (invalid parameter attributes)
  Major opcode of failed request:  70 (X_PolyFillRectangle)
  Serial number of failed request:  some number
  Current serial number in output stream:  some other number

   nedit needs rebuilding with a patch to work around an issue lesstif has
   with current X servers.

   Until this happemns, you can work around the issue by adding
   XLIB_SKIP_ARGB_VISUALS to your enviroment, e.g.
$ export XLIB_SKIP_ARGB_VISUALS=1
$ nedit

   3.10. I start my X server with startx or xinit and now all my X windows
   are contained within one large root Windows window? How do I get it
   back to each X window in it's own Windows window?

   This is a deliberate change from Cygwin/X X11 R6.9 behaviour.

    1. Start the X server using the "XWin Server" shortcut under
       "Cygwin-X" on the Start menu, or using startxwin.
       Note: If you wish to customize the X clients started when the X
       server starts, you can do so using a ~/.startxwinrc script.
    2. Alternatively, add the server option -multiwindow to your xinit or
       startx invocation, i.e. xinit -- -multiwindow or startx --
       -multiwindow
    3. Alternatively, put XWin -multiwindow into ~/.xserverrc or
       /etc/X11/xinit/xserverrc

   3.11. Moved question

   3.12. I upgraded and now X exits immediately after starting

   Since xinit-1.3.4-1, startxwin is now implemented by a script based on
   startx. Unfortunately, this has changed the behaviour in a
   backwards-incompatible way, as the X server is now killed when
   ~/.startxwinrc exits.

   If you have an empty ~/.startxwinrc, you should change it to contain
   exec sleep infinity so the X server will not exit until explicitly told
   to do so.

   If you are using a custom ~/.startxwinrc, either run the last client in
   the foreground (i.e. without &), so the X server exits when that client
   exits, or use exec sleep infinity as described above.

   You should also make sure that ~/.startxwinrc is executable (e.g. chmod
   +x ~/.startxwinrc).

   See the announce mail for more details.

   3.13. I upgraded and now X clients can't connect

   A1:

   Since X server 1.17, by default the server does not listen for TCP/IP
   connections, only accepting local connections on a unix domain socket.

   For local clients, use DISPLAY=:0.0, rather than DISPLAY=localhost:0.0,
   DISPLAY=127.0.0.1:0.0, DISPLAY=::1:0.0, etc. See Q: 1.6..

   A2:

   For remote clients, rather than connecting over TCP/IP by explicitly
   setting DISPLAY and allowing access using xhost or by disabling access
   control, use ssh tunnelling with ssh -Y instead. (See the User's Guide
   section on X forwarding using ssh for more details).

   A3:

   Use the -listen tcp option to restore the previous behaviour, allowing
   the X server to open a TCP/IP socket as well e.g. startxwin -- -listen
   tcp. See Q: 4.2..

4. Configuration

   4.1. Is there an xorg.conf or XF86Config file?

   No. Options which are configurable are available as command line
   options. For example, for more information on configuring other
   keyboard layouts using command line options, see Q: 5.1.1.

   4.2. What are the command line options for X? How do I add command line
   options for X?

   The Cygwin/X User's Guide and man XWin document the command line
   options for X.

   To supply a command line option to X:
     * If you use the start menu shortcut to start the X server, you will
       need to amend it's target to add an option, e.g.
       C:\cygwin\bin\run.exe --quote /usr/bin/bash.exe -l -c
       "/usr/bin/startxwin -- -nolock"

     Note: Note well that the entire command after -c is quoted

     Note: Note that this start menu shortcut is created by the xinit
     package, and your changes will be overwritten when the xinit package
     is updated.

     Note: Note that X server options to startxwin are preceded by --.
     * If you use startxwin, xinit or startx to start the server, run it
       as e.g. startxwin -- -nolock, xinit -- -nolock or startx -- -nolock
     * If you use startxwin.bat or startxwin.sh to start the server, add
       e.g. -nolock to the XWin line in that script.

   4.3. Why does X ignore the display depth that I pass on the command
   line?

   When running in windowed mode or GDI-based fullscreen mode, X must run
   the X Server at whatever display depth Windows is currently using; in
   these cases the display depth passed on the command line is ignored. X
   only uses the display depth parameter when running in a
   DirectDraw-based fullscreen mode, as DirectDraw allows applications to
   change the display resolution and depth when running in fullscreen
   mode.

   4.4. I have a two button mouse, can I emulate a three button mouse?

   Yes. Pass the -emulate3buttons timeout_in_milliseconds parameter to X,
   where timeout_in_milliseconds is the, optional, maximum number of
   milliseconds between a button release and opposite button press that
   will trigger an emulated third button press.

   4.5. Is there a Focus-Follows-Mouse feature (Auto-Focus)?

   This is a setting of the window manager used. The default window
   manager twm has no such feature. But with fvwm2 this can be achieved
   with the this configuration entry:
Focus FocusFollowsMouse

   Other window managers (eg. windowmaker) have similar features too.

   If you are using the -multiwindow mode you can not set this behaviour
   in the window manager but you can use the TweakUI tool to enable this
   feature for all windows, not limited to Cygwin/X windows.

   4.6. The option -nounixkill has no effect. How can i prevent the server
   shutdown an Ctrl-Alt-BackSpace?

   This question should be obsolete as the TerminateServer keybinding is
   no longer present by default.

   The TerminateServer keybinding can be enabled with
   setxkbmap -option terminate:ctrl_alt_bksp

   4.7. I have a multihead system. Do I need special options to make it
   work? I have a multihead system. Why are my X-application windows
   white?

   You should start X with the -multiplemonitors option.

   Note that this option is enabled by default in -multiwindow mode.

   4.8. I have a firewall. Is there anything I have to take care of?

   X uses port 6000/TCP when the option -listen tcp is used. You will have
   to allow incoming and outgoing traffic on this port even if you are
   only using local clients. X has a builtin access control so you won't
   have to worry about opening the port. If you are still concerned about
   security, you may limit the allowed hosts to the local IP addresses.

   If you use a different display number check section Q: 1.6. for details
   about which ports are used. For additional information about firewalls
   and XDMCP connections check Q: 7.3..

5. Internationalization

5.1. Keyboard support

   5.1.1. How do I use a non-U.S. keyboard layout?

   Some keyboard layouts are autodetected from the Windows keyboard
   settings. For these layouts no special change is needed. For all other
   layouts there is the possibility to configure the layout via
   commandline options.

   The main option for changing the layout is -xkblayout countrycode where
   countrycode is in most cases the 2 character code which also represents
   the country in internet adresses (e.g. Australia = au, Deutschland =
   de, France = fr, Japan = jp)

   Other options for tweaking the XKB layout are -xkbmodel,-xkbvariant,
   -xkboptions and -xkbrules. These are the counterparts for the similar
   named options known from the xorg.conf file.

   If the loading fails, check Q: 5.1.6.

   5.1.2. Is there a way to add a layout to the list of autodetected
   layouts?

   If your keyboard layout is not automatically detected you can send the
   required information for including it into Cygwin/X to
   cygwin@cygwin.com. Please include the following information in your
   mail:
     * The windows keyboard layout code and the layout name
       You will find it in /var/log/xwin/XWin.0.log in lines similar to
       these:

(--) winConfigKeyboard - Layout: "00001809" (00001809)
(EE) Keyboardlayout "Irish" (00001809) is unknown

     * The XKB layout code for this layout if you know it. Please
       experiment with setxkbmap or -xkblayout (as described in Q: 5.1.1.)
       to find an XKB layout code which works for you, otherwise the
       maintainers will have to guess it.
     * A description how the layout looks like. This makes it easy to
       identify the matching XKB layout code. Many layouts are available
       from the Microsoft Global Dev website (It seems that website only
       works with some browsers). Just add a link to your layout.

   5.1.3. Where can I find an xmodmap for my non-U.S. keyboard layout?

   This question should be obsolete The package xkeyboard-config should
   contain just about any needed layout

   Or, you can use xkeycaps to automatically generate a modmap for one of
   over 208 different layouts. See the xkeycaps home page to download and
   for more information.

   5.1.4. How do I get my non-U.S. keyboard modmap to be installed when
   using xdmcp?

   See Q: 5.1.1.

   5.1.5. Logging into AIX via XDMCP causes the keyboard to function as if
   AltGr is permanently pressed.

   [paraphrased from the Xming FAQ] AIX login scripts contain a call to
   xmodmap (for IBM keyboards) which causes the keyboard to be incorrectly
   configured for XWin. Commenting out those calls should allow you to use
   XWin with AIX.

   The XKB extension is now always enabled in the X.Org xserver, so the
   previous answer to this question of disabling the XKB extension with
   the -kb parameter is no longer applicable.

   5.1.6. Loading an XKB keyboard layout selected with -xkblayout fails

   Not all keyboard layouts are tested very well and some contain errors
   or do not work at all. To test if the compiling of your layout works
   start
setxkbmap de -print | xkbcomp -w3 -xkm - :0.0

   (replace the "de" with your layout code). This may produce warnings,
   but must not produce errors. If there are errors then please report
   them to the mailing list.

   5.1.7. I have Windows XP with Powertoys installed and AltGr does not
   work. What can I do?

   This question should be obsolete.

   5.1.8. AltGr does not work properly when connecting to various older
   commercial unices (e.g. HP-UX, AIX) or to old XFree86.

   xkeyboard-config XKB keyboard layouts generally have AltGr mapped as
   ISO_Level3_Shift to access additional characters on non-english
   keyboards. For reasons unknown to us, this is incompatible with some
   older X11 releases. We don't have access to such a machine, so we are
   unable to track this down and find a reason.

   It has been reported that sometimes it helps to run
DISPLAY=:0.0 setxkbmap languagecode

   from a cygwin shell after connecting.

   See this mailing list thread for more discussion and a possible
   workaround.

5.2. Display problems

   5.2.1. How do I get bash to display accents and/or umlauts?

   (Heinz Peter Hippenstiel) Add the following lines to .inputrc in your
   Cygwin home directory (e.g. ~/.inputrc):
set input-meta on    # to accept 8-bit characters
set output-meta on   # to show 8-bit characters
set convert-meta off # to show it as character, not the octal representation

   5.2.2. How do I put bash into "8 bit" mode?

   See Q: 5.2.1.

   5.2.3. How do I display unicode characters in an xterm?

   A1: for Cygwin 1.7

   If you have a UTF-8 locale configured, this should all just work :-).

   To confirm this is working properly, you may try the following:
$ wget http://www.cl.cam.ac.uk/~mgk25/ucs/examples/quickbrown.txt
[...]
$ cat quickbrown.txt

$ wget http://www.cl.cam.ac.uk/~mgk25/ucs/examples/UTF-8-demo.txt
[...]
$ cat UTF-8-demo.txt

   If you want to be able type unicode characters into this xterm, you'll
   need to configure your bash shell not to escape 8-bit characters, see
   Q: 5.2.1.

   A2: for Cygwin 1.5

   Start your xterm in UTF-8 mode as xterm +lc -u8.

   To confirm this is working properly, you may try the following
$ wget http://www.cl.cam.ac.uk/~mgk25/ucs/examples/quickbrown.txt
[...]
$ cat quickbrown.txt

   For reasons I don't currently understand, the default fixed font is
   only capable of supplying accented roman, hiragana and katakana
   characters, so if you wish to work with e.g. greek, cyrillic, hebrew,
   thai, etc. you'll need to start your xterm specifying a suitable font
   e.g. xterm +lc -u8 -fn
   -misc-fixed-medium-r-semicondensed--13-120-75-75-c-60-iso10646-1

   To confirm this is working properly, you may try the following
$ wget http://www.cl.cam.ac.uk/~mgk25/ucs/examples/UTF-8-demo.txt
[...]
$ cat UTF-8-demo.txt

   For other programs run from your xterm to output properly (e.g. less,
   which is why cat is used in the examples above), you may also need to
   set the LANG environment variable to LL_CC.UTF-8, where LL_CC is your
   language and country code.

   If you want to be able type unicode characters into this xterm, you'll
   need to configure your bash shell not to escape 8-bit characters, see
   Q: 5.2.1.

   See also the main Cygwin FAQ question on unicode support in Cygwin

6. Remote connections

   6.1. X11Forwarding does not work with OpenSSH under Cygwin

   A1:

   Try adding the -v option to ssh, which often pinpoints the reason for a
   connection problem.

   From the ssh man-page : -v Verbose mode. Causes ssh to print debugging
   messages about its progress. This is helpful in debugging connection,
   authentication, and configuration problems. Multiple -v options
   increase the verbosity. The maximum is 3.

   A2:

   Before establishing the ssh connection the xserver must be started and
   the environment variable DISPLAY must be set.
$ DISPLAY=:0.0
$ export DISPLAY
$ ssh -Y remotehost

   or
$ DISPLAY=:0.0 ssh -Y remotehost

   A3:

   Make sure you're not starting ssh with the option -X. Since OpenSSH
   7.2p1, ssh does not fallback to trusted forwarding, option -Y, so no
   X11 forwarding is setup. Use ssh -Y.

   Make sure you're not starting ssh with the option -x (lowercase). This
   disables X11 forwarding.

   A4:

   Check that X11Forwarding is not disabled in the ssh client
   configuration.

   The configfiles are by default ~/.ssh/config and /etc/ssh_config. The
   file in the home directory overrides settings in the global one.

   The configfile is split into various sections starting with "Host
   wildcard". The section applies to all hosts where wildcard matches the
   hostname.

   If this section contains an entry "ForwardX11 no" then X11Forwarding is
   disabled. To enable it change the entry to:
ForwardX11 yes

   A5:

   Check that X11Forwarding is not disabled in the ssh server
   configuration.

   The configfile is by default /etc/ssh/sshd_config. If there is an entry
   "X11Forwarding no" then X11Forwarding is disabled.

   If you have write access to the config file then change it to
X11Forwarding yes

   The OpenSSH server must be restarted or SIGHUP'ed to re-read the
   configuration file after it is changed. Otherwise, ask your
   administrator to change this for you.

   A6:

   [Frederick W. Wheeler] If the remote machine is a Windows machine using
   Cygwin OpenSSH server, make sure the Cygwin xauth package is installed
   on the remote machine. The OpenSSH server needs to be able to run xauth
   to do X11 Forwarding.

   6.2. Why do remote programs crash with an X Error of failed request:
   BadAtom? Why do remote programs exit when you try to copy and paste?

   This question should be obsolete since the SECURITY extension is now
   disabled

   OpenSSH 3.8 enables untrusted X11Forwarding by default when connecting
   to an ssh server that supports it.

   You will quickly notice that this is the case if most of your X
   applications are now killed when you try to copy and paste, X
   applications fail with an error similar to that below, or if xdpyinfo
   returns only a fraction of the supported extensions that it does if run
   locally.
 X Error of failed request: BadAtom (invalid Atom parameter)
  Major opcode of failed request: 18 (X_ChangeProperty)
  Atom id in failed request: 0x114
  Serial number of failed request: 370
  Current serial number in output stream: 372

   It is easiest to just override untrusted X11Forwarding by passing -Y to
   ssh in place of -X. The -Y does the same thing as -X, but it enables
   trusted X11 forwarding for the current connection.

   Setting "ForwardX11Trusted yes" in the ssh client configuration file
   does the same thing. See man ssh_config for more information.

   See also Q: 6.1.

   6.3. I'm confused about the difference between trusted and untrusted
   X11 forwarding. What does "Warning: untrusted X11 forwarding setup
   failed: xauth key data not generated" mean? Why is the SECURITY
   extension disabled?

   The warning means that ssh is going to use trusted X11 forwarding
   because untrusted X11 forwarding depends on the SECURITY extension,
   which isn't built into the X server and has been disabled by default
   upstream.

   Trusted X11 forwarding means that you trust the server that you wish to
   ssh into. The X server will allow remote clients to do whatever a local
   client would be able to do to your X session, for example, monitor your
   keypresses and take a screenshot. Such programs could be run by a
   malicious or compromised root user on the ssh server, or under your
   account if it was compromised on the ssh server.

   Starting with OpenSSH 3.8, untrusted forwarding is the default when X
   forwarding is requested using the -X command line option and you need
   to use the option -Y or specify "ForwardX11Trusted yes" in the client
   configuration for trusted forwarding by default.

   Since OpenSSH 7.2p1, untrusted forwarding (ssh -X) does not fallback to
   ssh -Y trusted forwarding.

   So why is this disabled? Untrusted X11 forwarding was meant to be a way
   to allow logins to unknown or insecure systems. It generates a cookie
   with xauth and uses the security extension to limit what the remote
   client is allowed to do. But this is widely considered to be not
   useful, because the security extension uses an arbitrary and limited
   access control policy, which results in a lot of applications not
   working correctly (e.g. not being able to cut and paste) and what is
   really a false sense of security. See this mail for more on the
   subject.

   (Words adapted from an email by Yaakov Selkowitz)

   6.4. What does "Warning: no xauth data; using fake authentication data
   for X11 forwarding" mean?

   Unless you started the X server with the -auth option (typically by
   using startx) this warning is expected and can safely be ignored.

   6.5. Why can't new remote X clients connect to the X server after 20
   minutes?

   Starting with OpenSSH 5.6, ssh enforces the ForwardX11Timeout (which
   defaults to 1200 seconds) when an untrusted connections is requested,
   even if an untrusted connection could not be made (e.g. you used ssh -X
   which asks for an untrusted connection, and got the "untrusted X11
   forwarding setup failed" warning). This means that no new connections
   to the X server can be made 20 minutes after the ssh connection is
   established.

   Use ssh -Y. See also Q: 6.2..

   6.6. Remote clients can't connect

   The X server now uses -nolisten tcp by default, which increases the
   security of the X server by not opening a TCP/IP socket.

   Use the -listen tcp option to allow the X server to open a TCP/IP
   socket as well, e.g. startxwin -- -listen tcp. See Q: 4.2..

   A better solution is to stop explicitly setting DISPLAY and allowing
   access using xhost or by disabling access control. Use ssh -Y instead.
   (See the User's Guide section on X forwarding using ssh for more
   details).

   6.7. X sessions forwarded by PuTTY can't connect. Non-cygwin local X
   clients can't connect.

   The X server now uses -nolisten tcp by default, which increases the
   security of the X server by not opening a TCP/IP socket, only a local
   (UNIX domain) socket. Non-cygwin applications cannot connect to that
   socket.

   Use the -listen tcp option to allow the X server to open a TCP/IP
   socket as well, e.g. startxwin -- -listen tcp. See Q: 4.2..

7. XDMCP connections

   7.1. XDMCP fatal error: Session declined No valid address

   Cygwin/X is sometimes unable to determine which local network
   interface's address should be reported to the XDMCP server; in these
   cases you need to pass -from local_host_name_or_ip_address to X to
   specify which interface address to report.

   7.2. Why does Cygwin/X report AUDIT: client 1 rejected from IP
   remotehost?

   The problem is most likely a wrong DNS (Network name resolution). Make
   sure your windows host has a hostname which is valid from linux too and
   an IP address which linux can resolve to that hostname.

   If you add a line
192.168.26.1 myhost

   to /etc/hosts on the XDMCP server with the IP address and the hostname
   of your windows host the name resolution should work.

   7.3. I get no login screen when using -query

   A1: Disabled XDMCP on servers

   [Mika Laitio] For security reasons, XDMCP is not enabled by default on
   most Linux/UNIX/*NIX/*BSD distributions (Red Hat, Mandrake, SuSE,
   FreeBSD, NetBSD, etc.) by default. You have to manually enable remote
   logins to your X Display Manager (e.g. xdm, kdm, or gdm). The location
   of the proper config file is distribution/OS dependent, but a short
   list of known config file locations is given in Table 1. You must
   change the line:
[Xdmcp]
Enable=false

   to:
[Xdmcp]
Enable=true

   or for xdm style configuration:
DisplayManager.requestPort:     0

   to:
!DisplayManager.requestPort:     0

   Table 1. Known XDM Configuration File Locations
   Distribution/OS  Version  Display Manager          Location
   Linux Mandrake   8.1      kdm             /usr/share/config/kdm/kdmrc
   Debian GNU/Linux Unstable kdm             /etc/kde3/kdm/kdmrc
   Debian GNU/Linux Unstable gdm             /etc/X11/gdm/gdm.conf
   Debian GNU/Linux Unstable xdm             /etc/X11/xdm/xdm-config
   Debian GNU/Linux Unstable wdm             /etc/X11/wdm/wdm-config

   A2: XDMCP and firewalls

   XDMCP will not work correctly if you have a personal firewall installed
   or the built-in firewall of Windows is activated.

   The XDMCP protocol will send and receive data on port 177/UDP. But the
   actual connections will be made to the local port 6000/TCP. It is safe
   to allow connections since the xserver has an own security layer. An
   overview of used ports is given in Table 2.

   Table 2. Ports used with XDMCP connections
   Port Protocol Direction Comment
   177 UDP Incoming/Outgoing Actual XDMCP connection
   6000+display TCP Incoming Connection for X11 clients. display is
   usually 0 except if you specify it on the commandline.

   7.4. XDMCP does not work with Mandrake 8.1

   See Q: 7.3.

   7.5. Why does GDM not work with -clipboard

   Newer versions of GDM have a more complex startup mechanism than the
   other display manager have. This can interfere with the way the
   clipboard integration client is started.

   Workaround: add (or modify) this section in the gdm.conf (or
   /etc/gdm/custom.conf) file.
[daemon]
KillInitClients=false

   7.6. I get no login screen for Solaris

   See also Q: 7.7. and Q: 7.8.

   [David Dawson] For whatever reason, certain versions of Solaris need
   fonts that are not provided by Cygwin/X; the result is that you may see
   the Solaris background tile and the hourglass cursor, but the XDM login
   prompt will never appear. The simplest solution is to point Cygwin/X at
   the font server that is usually running on the Solaris machine. You'll
   need a command line similar to the following to start your XDMCP
   session and to connect to the Solaris font server:

   X -query solaris_hostname_or_ip_address -fp
   tcp/solaris_hostname_or_ip_address:7100

     Note: The -fp parameter is a general X Server parameter, it is not
     specific to Cygwin/X; therefore, the -fp is documented in the X
     Server manual page. For additional information about fonts, see
     Fonts in X11R6.7.

   The standard port number for a font server is 7100, however, you may
   need to ask your system administrator what the font server port number
   is if you cannot connect to a font server on port 7100. It is also
   possible that your Solaris machine is not running a font server, in
   which case you will need to consult your Solaris documentation for
   instructions on how to run a font server.

   7.7. XDMCP freezes with remote Solaris machine!

   See also Q: 7.6. and Q: 7.8.

   Solaris appears to not support certain display bit depths, such as 24
   bits per pixel. Change your Windows display bit depth to 8, 16, or 32
   and try logging in again. File a complaint with Sun if this issue is
   important to you, or change your Solaris machines to use XFree86
   instead of the Solaris X Window System.

   7.8. Login to CDE on Solaris via XDMCP hangs Cygwin/X.

   See also Q: 7.6. and Q: 7.7.

   Install the recommended set of patches for your version of Solaris.

   7.9. Where can I find more information about XDMCP.

   See the Linux XDMCP HOWTO for more information about XDMCP.

8. Troubleshooting

   8.1. Cygwin/X failed with "Fatal Error". What does this mean?

   The Fatal Error is a general error message. More specific information
   what caused this is available in /var/log/xwin/XWin.0.log. Please check
   the common error messages in the Section called Error and Warning
   Messages. If your error is not mentioned proceed with Q: 8.4.

   8.2. Is there a log file that I can look at for diagnostic information
   and error messages?

   Yes. The Cygwin/X log file is located at /var/log/xwin/XWin.0.log. You
   will find solutions to the most common error messages in the Section
   called Error and Warning Messages.

   8.3. I have a specific error message, what does it mean?

   See the Error and Warning Messages section for help with specific error
   messages. Return to this section if you do not find a specific answer
   for the error message that you have.

   8.4. I have a specific error message that is not addressed in the Error
   and Warning Messages section.

   Search the Cygwin/X mailing list archives to see if the error message
   has already been reported and/or addressed. Report the error message to
   the cygwin@cygwin.com mailing list, how the error message was caused,
   and the behavior of the X Server after the error message was generated
   (exit, freeze, etc.), only if the error message has not been reported,
   if the circumstances that produced the error message are significantly
   different from other reports, or if you have additional information
   regarding the error message to contribute. Please include
   /var/log/xwin/XWin.0.log in your mail. This may help us identify the
   cause of your problem quicker.

   8.5. My bug report the Cygwin/X mailing list was ignored. What do I do
   now?

   Some bug reports are deliberately ignored by project members if the bug
   in question was recently dealt with; did you search the mailing list
   archives for a solution to your problem before submitting your bug
   report? Some bug reports are ignored if they do not contain sufficient
   information to understand the situation that produces the bug; did your
   bug report have enough information? Some bug reports are missed or
   forgotten, thus some valid bug reports do not receive a reply; simply
   resubmit such bug reports that have not received a response within 7
   days of submission.

   8.6. Why does Cygwin/X freeze right after startup?

   Zone Alarm 5 is known to break Cygwin/X. As a result you'll see this
   line (or a similar) as last output in /var/log/xwin/XWin.0.log
Rules = "xorg" Model = "pc101" Layout = "us" Variant = "(null)" Options = "(null
)"

   Disabling Zone Alarm will not solve this problem. You can only
   uninstall Zone Alarm 5 and switch to an earlier version (4.5 is known
   to work) or use a different personal firewall.

   Another reason is /tmp mounted in textmode. This does only happen with
   the -multiwindow and -clipboard switches because of the extra threads
   within Cygwin/X.

   You can remount /tmp to binmode with these commands:
mount -b "$(cygpath -m /tmp)" /tmp

   If this fails with an error message stating insufficient rights, try
mount -b -u "$(cygpath -m /tmp)" /tmp

   8.7. Cygwin/X has very poor performance. What's the reason?

   Most likely you have installed some kind of personal firewall, VPN
   software or any other software that modifies the TCP/IP stack of
   Windows. Especially Webwasher and some other filtering software are
   known to slow down the network traffic.

   Some online virus scanners like Symantec Antivirus do slowdown Cygwin/X
   a lot. They scan every file access and network traffic which causes
   serious processing overhead beyond that from the X11 protocol and the
   unix emulation layer.

   So far there is no known solution but to disable the virus scanner
   completely.

   [Dr. Edward Wornar] Certain programs that are installed by various
   drivers and software packages can consume an incredible amount of
   system resources and processing time. One known example of such a
   program is ATI2evxx.exe, a utility installed with some ATI Technologies
   graphics card drivers. Answers That Work has information on
   ATI2evxx.exe on their Task List Programs - A page. You may want to try
   disabling, one-by-one, ATI2evxx.exe and other such programs until you
   find the program that is causing the slowdown.

   8.8. I have Microsoft Services for Unix installed and can't type
   anything. Help me!!!

   Microsoft Services for Unix set some environment variables which points
   Cygwin/X to outdated or not existing files. These variables are
XAPPLRESDIR
XCMSDB
XKEYSYMDB
XNLSPATH

   To have Cygwin/X work correctly you have to unset at least XKEYSYMDB.

   Reported by Juan Medina, Pavel Rozenboim

   8.9. Cygwin/X is extremely slow, especially when using XDMCP to connect
   to remote machines.

   see Q: 8.7..

   8.10. Simulated mouse wheel scrolling doesn't work with a TrackPoint
   mouse (found on IBM laptops) or Synaptics Touchpads

   [Gerald S. Williams] The TrackPoint driver tries to send scroll up/down
   messages to the default scrollbar in a window. Cygwin/X does not use
   Windows scrollbars for X Client windows, so we must configure the
   TrackPoint driver to send standard WM_MOUSEWHEEL messages to the
   Cygwin/X window. This can be done by editing the TrackPoint
   configuration that can be found in the tp4table.dat and/or tp4scrol.dat
   files, which are usually located in %SYSTEM_ROOT%\System32\,
   %PROGRAMFILES%\Synaptics\SynTP\ or %PROGRAMFILES%\Lenovo\Trackpoint\.

   Add the following to the "Pass 0 rules"section and then restart your
   computer to ensure the driver reloads it's settings.
; X Windows
*,*,XWin.exe,*,*,*,WheelStd,0,9

   8.11. Why is the root window not shown in normal mode?

   This question should be obsolete.

   8.12. Why is the cross the default cursor in multiwindow mode?

   This question should be obsolete

   To workaround this add the command
   run xsetroot -cursor_name left_ptr -fg white -bg black

   to startxwin.bat

   8.13. How can I adjust the linewidth in bash after resizing XTerm?

   We think this question is probably obsolete

   Try starting resize.

   8.14. Why do some menus not work if Num-Lock is on?

   The problem are programs which treat Num-Lock as modifier similar to
   Control. The programs expect a plain click but received some strange
   Num-Lock-Click combination and can't associate this with the action
   "open menu".

9. Error and Warning Messages

   9.1. _XSERVTransmkdir: Owner of /tmp/.X11-unix should be set to root

_XSERVTransmkdir: Owner of /tmp/.X11-unix should be set to root
_XSERVTransmkdir: ERROR: euid != 0,directory /tmp/.X11-unix will not be created

   This question should be obsolete as this error is no longer generated.

   This warning message can be ignored; it does not cause any known
   problems.

   9.2. error opening security policy file
   /usr/X11R6/lib/X11/xserver/SecurityPolicy

   This question should be obsolete as this error is no longer generated.

   This error is harmless.

   9.3. Duplicate invocation on display number: 0. Exiting.

   Most likely you have started X twice.

   if you start multiple instances of X you have to give then unique
   display numbers

X -query foo
X :1 -query bar
X :2 -query blubb

   Specifying no display number is the same as using :0

   If you want another terminal window (which in fact is just a convenient
   side effect of running startxwin) you should do this by starting xterm
   & from an existing terminal window, from the notification area icon
   menu, from a cygwin shell or from the start menu.

   9.4. Fatal server error: could not open default font 'fixed'

   This question should be obsolete as the default font is now built into
   the server.

   This error occurs for one of three reasons:
    1. You do not have a font package which provides the default font
       ('fixed') installed. This is rarely the problem; but in the event
       that it is the problem, just rerun Cygwin' setup program, select
       the font-misc-misc package and install it.
    2. The mount point for /usr/share/fonts/ was either invalid (does not
       point to a valid folder on your system) or is a text-mode mount.
       You can confirm that this is the problem by running mount from a
       Cygwin shell and checking the disk path returned for the
       /usr/share/fonts/ mount point.

     Note: You cannot reliably fix this problem by deleting your Cygwin
     installation and reinstalling it. The mount points that Cygwin was
     using will be left in your system settings and the invalid mount
     point for /usr/share/fonts/ will be used again when you perform the
     reinstallation. You SHOULD follow the instructions below to fix the
     problem.
       To fix the problem, perform the following steps:
         a. Open a Cygwin shell and run umount /usr/share/fonts/.
         b. Close the Cygwin shell.
         c. Run Cygwin's setup program.
         d. For each of the font packages, if they are marked Keep, then
            select Reinstall, otherwise leave them as they are:
         e. Allow Cygwin's setup program to download and reinstall the
            fonts packages. The key to fixing this problem is that the
            files were previously untarred into an invalid location;
            removing the mount point for the fonts directory should result
            in the files being untarred to a valid location.
    3. You chose "DOS/text" as the "Default Text File type" during Cygwin
       setup, ignoring the advice that the Default Text File Type should
       be left on Unix/binary unless you have a very good reason to switch
       it to DOS/text.
       Open a Cygwin shell and run.

umount /usr/share/fonts/
mount -f -s -b "C:/cygwin/usr/share/fonts" "/usr/share/fonts"

       Reinstall your fonts

   9.5. Could not init font path element /usr/share/fonts/*/, removing
   from list!

   These warnings are generally harmless since they indicate that default
   search paths for fonts do not actually contain fonts; this is only a
   problem if the misc path does not contain fonts and/or all of the paths
   do not contain fonts.

   If you are getting these message and the X Server is also failing to
   start, then see Q: 9.4. for information on how to fix your fonts.

   9.6. The procedure entry point _check_for_executable could not be
   located

   This question should be obsolete.

   Programs that you are attempting to use were compiled against a newer
   version of Cygwin than is currently on your system. Run Cygwin's setup
   program to update your installation to the latest version.

   9.7. cygX11-6.dll not found after installation or upgrade

   This question should be obsolete.

   9.8. Exception: STATUS_ACCESS_VIOLATION

     * It is believed that this may have the same underlying causes as Q:
       9.16.
     * cygwin1.dll uses a shared memory section amongst all loaded copies
       of cygwin1.dll; unfortunately, the layout and usage of the shared
       memory section changes between versions of cygwin1.dll. Loading two
       different versions of cygwin1.dll will cause the shared memory
       section to become corrupted, which almost always results in an
       Exception: STATUS_ACCESS_VIOLATION. You must search your
       filesystem(s) and remove all copies of cygwin1.dll except the copy
       in /bin. You must remove the different versions of cygwin1.dll even
       if they are not in your path, as programs that depend on
       cygwin1.dll attempt to load the file from the local directory
       before searching other paths; thus, it is rather easy, and common,
       for multiple versions of cygwin1.dll to become loaded at the same
       time if they exist on a particular system.
     * See also this main Cygwin FAQ question for an issue which may cause
       this problem with older binaries on Terminal Server.

   9.9. Xlib: connection to "local_host_name_or_ip_address:0.0" refused by
   server Xlib: Maximum number of clients reached

   Cygwin/X queries getdtablesize() for the maximum number of client
   connections allowed; by default Cygwin returns 32 from getdtablesize().
   Cygwin/X Server Test Series release Test44, released on 2001-08-15,
   changed the maximum number of clients from 32 to 1024 by passing the
   square of getdtablesize() to setdtablesize().

   9.10. XIO: fatal IO error 104 (Connection reset by peer) on X server
   "127.0.0.1:0.0"

   See Q: 9.9.

   9.11. Cannot Open Display: 127.0.0.1:0.0

   Certain classes of software, such as that used for Virtual Private
   Networking and fire-walling may cause the IP address 127.0.0.1, or
   other local adapter addresses, to be redirected, to become inoperable
   in some way, or to be operated in a manner that violates the defined
   operation of IP address.

   As a potential remedy, try removing all instances of such software;
   this may not always fix the problem though, as some software may leave
   artifacts even after uninstallation is completed. The only way to be
   sure that you have not found a Cygwin/X bug is to install Windows on a
   freshly formatted hard drive, followed by Cygwin and Cygwin/X, and
   finally add your other software one application at a time until
   Cygwin/X stops working.

   Some products that have been reported to cause problems:
     * Aventail Connect
     * Zonealarm PC Firewall from Zonelab

     Note: These products may not cause problems in all configurations.
     However, the Cygwin/X project has neither the time, ability, nor
     resources to help you correctly configure your third-party software.

   See the main Cygwin FAQ question for an up-to-date list of software
   which has been known to interfere with the correct operation of Cygwin.

   9.12. Out of environment space

   Increase your Windows environment space by following the instructions
   provided by Microsoft.

   9.13. Too many parameters

   See Q: 9.12.

   9.14. "xcb_xlib_lock: Assertion '!c->xlib.lock' failed." or
   "xcb_xlib_unlock: Assertion 'c->xlib.lock' failed."

   This question should be obsolete.

   Both of these represent bugs in a caller of libX11, and not in libX11
   or libxcb. The first assertion means that a caller attempted to lock
   the display while already locked. The second assertion means that a
   caller attempted to unlock the display without having it locked.

   If you encounter such bugs, please report a bug against the offending
   software (which is not libX11 or libxcb)

   This error can be worked around by using export
   LIBXCB_ALLOW_SLOPPY_LOCK=1

   9.15. Fatal server error: Failed to activate core devices.

(EE) XKB: Could not invoke xkbcomp
(EE) XKB: Couldn't compile keymap
XKB: Failed to compile keymap
Keyboard initialization failed. This could be a missing or incorrect setup of xk
eyboard-config.
Fatal server error: Failed to activate core devices.

     * Verify that xkeyboard-config is correctly installed using cygcheck
       -c xkeyboard-config,
     * Check that /usr/bin/xkbcomp can be run from a bash shell. If that
       fails, see if cygcheck /usr/bin/xkbcomp reports any missing DLLs.
     * Something is interferring with the ability of the X server to
       invoke xkbcomp to compile the keymap.
       See Q: 9.16. for possible causes.

   9.16. "fatal error - unable to remap (some dll) to same address as
   parent: (some hex number) != (some other hex number)" or "(some dll):
   Loaded to different address: parent(some hex number) != child(some
   other hex number)"

   This is commonly caused by one of three things:
     * You have run Cygwin's setup program to do an update while some
       cygwin processes were running, and then clicked on the continue
       option in the "In-use files detected" dialog, and then tried to
       carry on using Cygwin without rebooting as advised by setup.
       Reboot.
     * This is one of the symptoms of an application interfering with
       Cygwin's fork() emulation. See the main Cygwin FAQ question for a
       list of software which has been known to interfere with the correct
       operation of Cygwin.
     * This also caused by DLLs with conflicting base addresses preventing
       Cygwin's fork() emulation from functioning correctly. See the main
       Cygwin FAQ question for advice.

   9.17. fork: child -1 - died waiting for longjmp before initialization,
   retry (some number), exit code (some hex number), errno (some other
   number)

   This is believed to have the same underlying causes as Q: 9.16.

10. Porting Software

   10.1. Is there a list of software that has been ported to Cygwin/X?

   Look in Cygwin's setup program for packages in the X11 category.

   10.2. How do I start porting software to Cygwin/X?

   Cygwin/X provides a software interface that is very similar to the
   software interface provided by GNU/Linux and other UNIX systems. Most
   software packages will compile on Cygwin/X without any changes at all.
   To begin with, try to compile a given software package following that
   package's compilation instructions for GNU/Linux.

   10.3. Are there common problems encountered when porting software to
   Cygwin/X?

   One common problem encountered when porting software to Cygwin/X is due
   to Cygwin's inability to distinguish between files with the same name
   but different capitalization (e.g. XvMC.h and xvmc.h), which is due to
   a Windows' limitation.

   Example 1. Include Problems

   This example is based off an error that actually occurred in the source
   code tree in xc/programs/Xserver/Xext/xvmc.c. xvmc.c included XvMC.h,
   as shown below:
#include "XvMC.h"

   The intention was to include the file xc/include/extensions/XvMC.h.
   Unfortunately, there was a file named xc/programs/Xserver/Xext/xvmc.h
   that ended up getting included instead of the desired file, because the
   precompiler searched the local directory, xc/programs/Xserver/Xext/,
   before searching the rest of the include path. Cygwin can't distinguish
   between XvMC.h and xvmc.h, so xvmc.h ended up being included in xvmc.c.
   The build process on Cygwin broke because the contents of XvMC.h were
   entirely different than the contents of xvmc.h.

   The solution was to change the include to specifically reference the
   desired header:
#include "../../../include/extensions/XvMC.h"

   10.4. Problems building or linking OpenGL applications? Undefined
   reference to _glsomething?

   Cygwin has two OpenGL implementations:
    1. headers in /usr/include/w32api/GL, libraries (-lglut32 -lglu32
       -lopengl32) from the opengl and w32api packages which are for
       displaying OpenGL graphics directly through the native Windows
       interface (Win32) without any X server
    2. headers in /usr/include/GL, libraries (-lglut -lglu -lgl) from the
       Mesa libGL packages (libGL-devel, libGL1, libGLU-devel, libGLU1,
       libglut-devel, libglut3) which are for displaying OpenGL graphics
       through an X server.

   These are incompatible, even the headers (e.g. the native OpenGL API
   has the stdcall calling convention on x86), so you must exercise care
   if you have both sets of devel packages installed. An application must
   be built using only one of these.
     * X applications using GLX must be built using option 2.
     * Applications using GLUT have a choice.
     * Applications using the WGL API must be built using option 1.

   (Words adapted from an email by André Bleau)

11. Contributing

   11.1. Are there step-by-step instructions for contributing to Cygwin/X?

   Yes. The Cygwin/X Contributor's Guide has step-by-step instructions for
   obtaining the source, building the source, building debug versions of
   the source, and even cross-compiling under Linux.

   11.2. Are there editors for Windows that understand and preserve UNIX
   end of line characters?

   Yes. Emacs and XEmacs are available for Windows; they both understand
   and preserve UNIX end of line characters.

   11.3. How should I generate patches for Cygwin/X?

   Only submit patches that have UNIX end of line characters. See Q: 11.2.
   for information on editors for Windows that are aware of UNIX end of
   line characters.

   11.4. Where do I submit patches for Cygwin/X?

   Submit patches for Cygwin/X to the cygwin@cygwin.com mailing list.

   See Q: 11.3. for more information on generating patches.

   11.5. Why doesn't the X Window System use GNU's autoconf?

   It does! Thanks to the excellent efforts of the X.Org community, the X
   Window System has been autotoolized since X.Org R7.0.

   Anyone who despaired of touching the monolithic tree will find things
   much easier now with modular packages.

   11.6. What compiler does Cygwin/X use, and which compilers are
   supported?

   Cygwin/X uses the gcc compiler from the Free Software Foundation.
   Cygwin/X source code is mostly ANSI C compliant, but we cannot
   guarantee that Cygwin/X will compile with any other compiler, nor can
   we afford the time to support compilers other than gcc.

   See the GCC Home Page for more information on gcc.

   11.7. Is cross-compiling from a non-Cygwin platform supported?

   Cross-compiling from a non-Cygwin platform is described in the Cygwin/X
   Contributor's Guide

   11.8. Where can I get help for installing DocBook on Cygwin?

   The required packages are listed in the Cygwin/X Contributor's Guide.

12. Licenses, Patents, Trademarks, and Copyrights

   12.1. What licenses apply to Cygwin/X source code?

   Cygwin/X proper isn't covered by a single license, as Cygwin/X is made
   up of two parts that are covered by distinct licenses: Cygwin and the X
   Window System.

   See Q: 12.2. and Q: 12.3. for more information regarding the licenses
   that apply to Cygwin/X.

   12.2. What licenses apply to the X Window System source code?

   X Window System source code is generally licensed under an X11 style
   license, which is certified by the Free Software Foundation as
   compatible with the GNU GPL.

   12.3. What license applies to Cygwin source code?

   Cygwin source code is licensed under a modified version of the GNU GPL
   . Cygwin's license modification specifically allows third-party
   software under an open source license to be linked with Cygwin without
   requiring that the source code for the third-party software be
   distributed under the terms of the GNU GPL. Cygwin's developers went to
   great trouble to obtain this modification and should be thanked for
   doing so, as without it the modification, Cygwin/X linking to Cygwin
   would be the subject of endless discussion.

   12.4. Who holds the copyright on the Cygwin/X source code?

   Cygwin/X proper doesn't have a single copyright holder, as Cygwin/X is
   made up of two parts, namely Cygwin and the X Window System; each part
   follows a different scheme in regards to who will hold the copyright on
   source code.

   See Q: 12.5. and Q: 12.6. for more information regarding who holds the
   copyright on Cygwin/X source code.

   12.5. Who holds the copyright on the X Window System source code?

   Each source code file in the X Window System typically has its own
   license and copyright statement. Therefore, there is not a general rule
   for determining who holds the copyright on a particular X Window System
   source file, as each author is free to assign the copyright to someone
   else, to some group, or to keep the copyright themselves. You must
   inspect the source code file in question to determine who holds the
   copyright for that file.

   12.6. Who holds the copyright on the Cygwin source code?

   Red Hat owns the copyright on the Cygwin source code. Red Hat requires
   that copyright be assigned to Red Hat for non-trivial changes to
   Cygwin. You must fill out a copyright transfer form if you are going to
   contribute substantial changes to Cygwin.

   12.7. What license applies to Motif?

   Motif is a product of The Open Group. After many years under the The
   Open Group Public License (which does not satisfy the Open Source
   Definition and is thus not compatible with Cygwin's license), Motif was
   released as free software under the LGPL v2.1 in October 2012.

   12.8. Isn't "XWin" trademarked by StarNet Communications?

   Not in the USA, at least. A quick search at the United States Patent
   and Trademark Office for "XWin" turns up one dead record and one live
   record. The live record is for a logo belonging to a rock crusher
   manufacturer based out of Belgium. Neither trademark affects Cygwin/X,
   as the dead record is no longer enforceable, while the live record is
   in an unrelated and distinct industry; there cannot be confusion
   between rock crushers and computer programs.
     __________________________________________________________________

Bibliography

Books

   [ScheiflerGettys92] Robert W. Scheifler, James Gettys, Jim Flowers, and
   David Rosenthal, 1992, 1-55558-088-2, Butterworth-Heinemann, X Window
   System: The Complete Reference to Xlib, X Protocol, ICCCM, and XLFD.

   [Richter99] Jeffrey Richter, 1999, 1-57231-996-8, Microsoft Press,
   Programming Applications for Microsoft Windows: Mastering the critical
   building blocks of 32-bit and 64-bit Windows-based applications.

   [Petzold99] Charles Petzold, 1999, 1-57231-995-X, Microsoft Press,
   Programming Windows: The definitive guide to the Win32 API.

   [McKay99] Everett N. McKay, 1999, 0-7356-0586-6, Microsoft Press,
   Developing User Interfaces for Microsoft Windows: Practical and
   effective methods for improving the user experience.

   [JonesOhlund99] Anthony Jones and Jim Ohlund, 1999, 0-7356-0560-2,
   Microsoft Press, Network Programming for Microsoft Windows: Clear,
   practical guide to Microsoft's networking APIs.

   [Yuan01] Feng Yuan, 2001, 0-13-086985-6, Prentice Hall PTR, Windows
   Graphics Programming: Win32 GDI and DirectDraw.

   [CohenWoodring98] Aaron Cohen and Mike Woodring, 1998, 1-56592-296-4,
   O'Reilly & Associates, Inc., Win32 Multithreaded Programming: Building
   Thread-Safe Applications.

   [CameronRosenblattRaymond96] Debra Cameron, Bill Rosenblatt, and Eric
   Raymond, 1996, 1991, 1-56592-152-6, O'Reilly & Associates, Inc.,
   Learning GNU Emacs: UNIX Text Processing.

   [Lewine91] Edited by Dale Dougherty, Donald A. Lewine, 1991,
   0-937175-73-0, O'Reilly & Associates, Inc., POSIX Programmer's Guide:
   Writing Portable UNIX Programs.

   [KernighanRitchie88] Brian W. Kernighan and Dennis M. Ritchie, 1988,
   1978, 0-13-110370-9, Prentice Hall PTR, The C Programming Language:
   ANSI C.

Glossary

F

   firewall
          Firewall software attempts to protect an internal network from
          intrusions originating from an external network.

V

   Virtual Private Network (VPN)
          Virtual Private Networks are encrypted tunnels through which
          private data can be safely transmitted over a private network
          (e.g. the Internet).

X

   X Display Manager (XDM)
          An X Display Manager presents a graphical login screen to X
          users. Often an XDM will allow the user to select a desktop
          environment or window manager to be for their login session.
          Some X Display Managers are xdm, gdm (Gnome Display Manager),
          and kdm (KDE Display Manager).

   X Display Manager Control Protocol (XDMCP)
          XDMCP allows XDM to process logins for users remote to the
          machine that XDM is running on; login sessions will be run on
          the machine running XDM. For example, at a university you may
          use XDMCP to login to an X session running on an engineering
          department computer from your dorm room.

          See Also: X Display Manager.

   X11 Forwarding
          Some SSH programs like OpenSSH provide a feature where in
          addition to the normal text channel opened between the local and
          the remote host another encrypted channel is opened for the
          communication between the X11 client and the X11 server. The SSH
          server will act as proxy-server for the X11 clients and will
          forward all communication to the X11 server.
     __________________________________________________________________

A. GNU Free Documentation License

   Version 1.3, 3 November 2008

   Copyright � 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc.

   Everyone is permitted to copy and distribute verbatim copies of this
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       giving the public permission to use the Modified Version under the
       terms of this License, in the form shown in the Addendum below.
    G. Preserve in that license notice the full lists of Invariant
       Sections and required Cover Texts given in the Document’s license
       notice.
    H. Include an unaltered copy of this License.
    I. Preserve the section Entitled “History”, Preserve its Title, and
       add to it an item stating at least the title, year, new authors,
       and publisher of the Modified Version as given on the Title Page.
       If there is no section Entitled “History” in the Document, create
       one stating the title, year, authors, and publisher of the Document
       as given on its Title Page, then add an item describing the
       Modified Version as stated in the previous sentence.
    J. Preserve the network location, if any, given in the Document for
       public access to a Transparent copy of the Document, and likewise
       the network locations given in the Document for previous versions
       it was based on. These may be placed in the “History” section. You
       may omit a network location for a work that was published at least
       four years before the Document itself, or if the original publisher
       of the version it refers to gives permission.
    K. For any section Entitled “Acknowledgements” or “Dedications”,
       Preserve the Title of the section, and preserve in the section all
       the substance and tone of each of the contributor acknowledgements
       and/or dedications given therein.
    L. Preserve all the Invariant Sections of the Document, unaltered in
       their text and in their titles. Section numbers or the equivalent
       are not considered part of the section titles.
    M. Delete any section Entitled “Endorsements”. Such a section may not
       be included in the Modified Version.
    N. Do not retitle any existing section to be Entitled “Endorsements”
       or to conflict in title with any Invariant Section.
    O. Preserve any Warranty Disclaimers.

   If the Modified Version includes new front-matter sections or
   appendices that qualify as Secondary Sections and contain no material
   copied from the Document, you may at your option designate some or all
   of these sections as invariant. To do this, add their titles to the
   list of Invariant Sections in the Modified Version’s license notice.
   These titles must be distinct from any other section titles.

   You may add a section Entitled “Endorsements”, provided it contains
   nothing but endorsements of your Modified Version by various parties —
   for example, statements of peer review or that the text has been
   approved by an organization as the authoritative definition of a
   standard.

   You may add a passage of up to five words as a Front-Cover Text, and a
   passage of up to 25 words as a Back-Cover Text, to the end of the list
   of Cover Texts in the Modified Version. Only one passage of Front-Cover
   Text and one of Back-Cover Text may be added by (or through
   arrangements made by) any one entity. If the Document already includes
   a cover text for the same cover, previously added by you or by
   arrangement made by the same entity you are acting on behalf of, you
   may not add another; but you may replace the old one, on explicit
   permission from the previous publisher that added the old one.

   The author(s) and publisher(s) of the Document do not by this License
   give permission to use their names for publicity for or to assert or
   imply endorsement of any Modified Version.

5. COMBINING DOCUMENTS

   You may combine the Document with other documents released under this
   License, under the terms defined in section 4 above for modified
   versions, provided that you include in the combination all of the
   Invariant Sections of all of the original documents, unmodified, and
   list them all as Invariant Sections of your combined work in its
   license notice, and that you preserve all their Warranty Disclaimers.

   The combined work need only contain one copy of this License, and
   multiple identical Invariant Sections may be replaced with a single
   copy. If there are multiple Invariant Sections with the same name but
   different contents, make the title of each such section unique by
   adding at the end of it, in parentheses, the name of the original
   author or publisher of that section if known, or else a unique number.
   Make the same adjustment to the section titles in the list of Invariant
   Sections in the license notice of the combined work.

   In the combination, you must combine any sections Entitled “History” in
   the various original documents, forming one section Entitled “History”;
   likewise combine any sections Entitled “Acknowledgements”, and any
   sections Entitled “Dedications”. You must delete all sections Entitled
   “Endorsements”.

6. COLLECTIONS OF DOCUMENTS

   You may make a collection consisting of the Document and other
   documents released under this License, and replace the individual
   copies of this License in the various documents with a single copy that
   is included in the collection, provided that you follow the rules of
   this License for verbatim copying of each of the documents in all other
   respects.

   You may extract a single document from such a collection, and
   distribute it individually under this License, provided you insert a
   copy of this License into the extracted document, and follow this
   License in all other respects regarding verbatim copying of that
   document.

7. AGGREGATION WITH INDEPENDENT WORKS

   A compilation of the Document or its derivatives with other separate
   and independent documents or works, in or on a volume of a storage or
   distribution medium, is called an “aggregate” if the copyright
   resulting from the compilation is not used to limit the legal rights of
   the compilation’s users beyond what the individual works permit. When
   the Document is included in an aggregate, this License does not apply
   to the other works in the aggregate which are not themselves derivative
   works of the Document.

   If the Cover Text requirement of section 3 is applicable to these
   copies of the Document, then if the Document is less than one half of
   the entire aggregate, the Document’s Cover Texts may be placed on
   covers that bracket the Document within the aggregate, or the
   electronic equivalent of covers if the Document is in electronic form.
   Otherwise they must appear on printed covers that bracket the whole
   aggregate.

8. TRANSLATION

   Translation is considered a kind of modification, so you may distribute
   translations of the Document under the terms of section 4. Replacing
   Invariant Sections with translations requires special permission from
   their copyright holders, but you may include translations of some or
   all Invariant Sections in addition to the original versions of these
   Invariant Sections. You may include a translation of this License, and
   all the license notices in the Document, and any Warranty Disclaimers,
   provided that you also include the original English version of this
   License and the original versions of those notices and disclaimers. In
   case of a disagreement between the translation and the original version
   of this License or a notice or disclaimer, the original version will
   prevail.

   If a section in the Document is Entitled “Acknowledgements”,
   “Dedications”, or “History”, the requirement (section 4) to Preserve
   its Title (section 1) will typically require changing the actual title.

9. TERMINATION

   You may not copy, modify, sublicense, or distribute the Document except
   as expressly provided under this License. Any attempt otherwise to
   copy, modify, sublicense, or distribute it is void, and will
   automatically terminate your rights under this License.

   However, if you cease all violation of this License, then your license
   from a particular copyright holder is reinstated (a) provisionally,
   unless and until the copyright holder explicitly and finally terminates
   your license, and (b) permanently, if the copyright holder fails to
   notify you of the violation by some reasonable means prior to 60 days
   after the cessation.

   Moreover, your license from a particular copyright holder is reinstated
   permanently if the copyright holder notifies you of the violation by
   some reasonable means, this is the first time you have received notice
   of violation of this License (for any work) from that copyright holder,
   and you cure the violation prior to 30 days after your receipt of the
   notice.

   Termination of your rights under this section does not terminate the
   licenses of parties who have received copies or rights from you under
   this License. If your rights have been terminated and not permanently
   reinstated, receipt of a copy of some or all of the same material does
   not give you any rights to use it.

10. FUTURE REVISIONS OF THIS LICENSE

   The Free Software Foundation may publish new, revised versions of the
   GNU Free Documentation License from time to time. Such new versions
   will be similar in spirit to the present version, but may differ in
   detail to address new problems or concerns. See Copyleft.

   Each version of the License is given a distinguishing version number.
   If the Document specifies that a particular numbered version of this
   License “or any later version” applies to it, you have the option of
   following the terms and conditions either of that specified version or
   of any later version that has been published (not as a draft) by the
   Free Software Foundation. If the Document does not specify a version
   number of this License, you may choose any version ever published (not
   as a draft) by the Free Software Foundation. If the Document specifies
   that a proxy can decide which future versions of this License can be
   used, that proxy’s public statement of acceptance of a version
   permanently authorizes you to choose that version for the Document.

11. RELICENSING

   “Massive Multiauthor Collaboration Site” (or “MMC Site”) means any
   World Wide Web server that publishes copyrightable works and also
   provides prominent facilities for anybody to edit those works. A public
   wiki that anybody can edit is an example of such a server. A “Massive
   Multiauthor Collaboration” (or “MMC”) contained in the site means any
   set of copyrightable works thus published on the MMC site.

   “CC-BY-SA” means the Creative Commons Attribution-Share Alike 3.0
   license published by Creative Commons Corporation, a not-for-profit
   corporation with a principal place of business in San Francisco,
   California, as well as future copyleft versions of that license
   published by that same organization.

   “Incorporate” means to publish or republish a Document, in whole or in
   part, as part of another Document.

   An MMC is “eligible for relicensing” if it is licensed under this
   License, and if all works that were first published under this License
   somewhere other than this MMC, and subsequently incorporated in whole
   or in part into the MMC, (1) had no cover texts or invariant sections,
   and (2) were thus incorporated prior to November 1, 2008.

   The operator of an MMC Site may republish an MMC contained in the site
   under CC-BY-SA on the same site at any time before August 1, 2009,
   provided the MMC is eligible for relicensing.

ADDENDUM: How to use this License for your documents

   To use this License in a document you have written, include a copy of
   the License in the document and put the following copyright and license
   notices just after the title page:
Copyright � YEAR YOUR NAME

Permission is granted to copy, distribute and/or modify this document under the
terms of the GNU Free Documentation License, Version 1.3 or any later version
published by the Free Software Foundation; with no Invariant Sections, no
Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in
the section entitled “GNU Free Documentation License”.

   If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts,
   replace the “with… Texts.” line with this:
with the Invariant Sections being LIST THEIR TITLES, with the Front-Cover Texts
being LIST, and with the Back-Cover Texts being LIST.

   If you have Invariant Sections without Cover Texts, or some other
   combination of the three, merge those two alternatives to suit the
   situation.

   If your document contains nontrivial examples of program code, we
   recommend releasing these examples in parallel under your choice of
   free software license, such as the GNU General Public License, to
   permit their use in free software.
