Linux系统中Xwindow系统启动脚本分析.doc

Linux100中文网 Linux系统中Xwindow系统启动脚本分析 安装了Linux后当然希望能进入XWindow，象在Windows一样方便地工作，于是大家都可能用过startx命令，也可能是直接在XWindow登录界面进入XWindow。这两种方式的XWindow启动过程有没有区别呢？如果你没有做过个性化设置可能体会不到，但如果你设置过中文输入法，不管是用SCIM还是fcitx，可能都有过设置输入法为随XWindow启动的经验。朋友们开始修改各种启动脚本，经常可能会修改到的方法有：1、修改/etc/X11/xinit/xinitrc2、修改/etc/X11/Xsession3、在/etc/X11/Xsession.d目录下增加一个自定义的脚本4、修改$HOME/.xsession5、修改$HOME/.xinitrc6、修改/etc/X11/xdm/Xsession 总之，看起来是八仙过海各有各的神通了。这些方法有没有不同？为什么有时候明明设置好了，startx起来可以用了，但重启在XWindow管理界面登录后却不能用了？为什么有时从XWindow管理界面登录后可用，但startx后却用不了？下面我们一起来分析一下吧。 #!/bin/sh# /etc/X11/Xsession# global Xsession file - used by display managers and xinit (startx)# $Id: Xsession 2186 2005-02-11 07:11:05Z branden $set -ePROGNAME=Xsessionmessage () # pretty-print messages of arbitrary length; use xmessage if it# is available and $DISPLAY is setMESSAGE=“$PROGNAME: $*”echo”$MESSAGE” | fold -s -w $COLUMNS:-80 2if -n”$DISPLAY” which xmessage /dev/null 21; thenecho”$MESSAGE” | fold -s -w $COLUMNS:-80 | xmessage -center -file -fimessage_nonl () # pretty-print messages of arbitrary length (no trailing newline); use# xmessage if it is available and $DISPLAY is setMESSAGE=“$PROGNAME: $*”echo -n”$MESSAGE” | fold -s -w $COLUMNS:-80 2;if -n”$DISPLAY” which xmessage /dev/null 21; thenecho -n”$MESSAGE” | fold -s -w $COLUMNS:-80 | xmessage -center -file -fierrormsg () # exit script with errormessage”$*”exit 1internal_errormsg () # exit script with error; essentially a”THIS SHOULD NEVER HAPPEN” message# One big call to message() for the sake of xmessage; if we had two then# the user would have dismissed the error we want reported before seeing the# request to report it.errormsg”$*” “Please report the installed version of the ”xfree86-common”“ “package and the complete text of this error message to” “.”# initialize variables for use by all session scriptsOPTIONFILE=/etc/X11/Xsession.optionsSYSRESOURCES=/etc/X11/XresourcesUSRRESOURCES=$HOME/.XresourcesSYSSESSIONDIR=/etc/X11/Xsession.dUSERXSESSION=$HOME/.xsessionALTUSERXSESSION=$HOME/.XsessionERRFILE=$HOME/.xsession-errors# attempt to create an error file; abort if we cannotif touch”$ERRFILE” 2 /dev/null -w”$ERRFILE” ! -L”$ERRFILE” ; thenchmod 600”$ERRFILE”elif ERRFILE=$(tempfile 2 /dev/null); thenif ! ln -sf”$ERRFILE”$TMPDIR:=/tmp/xsession-$USER”; thenmessage”warning: unable to symlink ”$TMPDIR/xsession-$USER” to” “”$ERRFILE”; look for session log/errors in” “”$TMPDIR/xsession-$USER”.”fielseerrormsg”unable to create X session log/error file; aborting.”fiexec ”$ERRFILE” 21echo”$PROGNAME: X session started for $LOGNAME at $(date)”# sanity check; is our session script directory present?if ! -d”$SYSSESSIONDIR” ; thenerrormsg”no ”$SYSSESSIONDIR” directory found; aborting.”fi# Attempt to create a file of non-zero length in /tmp; a full filesystem can# cause mysterious X session failures. We do not use touch, :, or test -w# because they wont actually create a file with contents. We also let standard# error from tempfile and echo go to the error file to aid the user in# determining what went wrong.WRITE_TEST=$(tempfile)if ! echo”*” ”$WRITE_TEST”; thenmessage”warning: unable to write to $WRITE_TEST%/*; X session may exit” “with an error”firm -f”$WRITE_TEST”# Use run-parts to source every file in the session directory; we source# instead of executing so that the variables and functions defined above# are available to the scripts, and so that they can pass variables to each# other.SESSIONFILES=$(run-parts -list $SYSSESSIONDIR)if -n”$SESSIONFILES” ; thenfor SESSIONFILE in $SESSIONFILES; do. $SESSIONFILEdonefiexit 0 此文件的第五行“# global Xsession file - used bydisplay managers and xinit(startx)”已经说明/etc/X11/Xsession脚本是大家公用的，无论你是用XWindow管理器（比如kdm、gdm、xdm）进入还是通过命令行输入startx（即xinit方式）进入XWindow，都会调用此脚本程序。再看看这个脚本程序做了些什么吧。这一行“SYSSESSIONDIR=/etc/X11/Xsession.d”定义了一个变量指向了目录/etc/X11/Xsession.d，后面又出现一段代码： SESSIONFILES=$(run-parts -list $SYSSESSIONDIR)if -n”$SESSIONFILES” ; thenfor SESSIONFILE in $SESSIONFILES; do. $SESSIONFILEdonefi 显然这里是搜索了目录/etc/X11/Xsession.d里面所有的脚本并一一执行完毕。同时请注意有这么两行： USERXSESSION=$HOME/.xsessionALTUSERXSESSION=$HOME/.Xsession 在这里并没有看到使用这两个变量，那么在这个脚本里定义来做什么？下面再看一下脚本/etc/X11/Xsession.d/50xfree86-common_determine-startup里的内容，原文如下： # $Id: 50xfree86-common_determine-startup 1437 2004-05-23 03:18:32Z branden $# This file is sourced by Xsession(5), not executed.# If no X session startup program was passed to the Xsession script as an# argument (e.g., by the display manager), or if that program was not# executable, fall back to looking for a userot; doif -e”$STARTUPFILE” ; thenif -x”$STARTUPFILE” ; thenSTARTUP=“$STARTUPFILE”elseSTARTUP=“sh $STARTUPFILE”fibreakfidonefifi# If there is still nothing to use for a startup program, try the system# default session manager, window manager, and terminal emulator.if -z”$STARTUP” ; thenif -x /usr/bin/x-session-manager ; thenSTARTUP=x-session-managerelif -x /usr/bin/x-window-manager ; thenSTARTUP=x-window-managerelif -x /usr/bin/x-terminal-emulator ; thenSTARTUP=x-terminal-emulatorfifi# If we still have not found a startup program, give up.if -z”$STAfierrormsg”$ERRMSG no session managers, no window managers, and no terminal” “emulators found; aborting.”fi# vim:set ai et sts=2 sw=2 tw=80: 这一行“# This file is sourced by Xsession(5), not executed.”证明脚本是被之前的/etc/X11/Xsession调用的，而后面这一段： for STARTUPFILE in”$USERXSESSION”$ALTUSERXSESSION”; doif -e”$STARTUPFILE” ; thenif -x”$STARTUPFILE” ; thenSTARTUP=“$STARTUPFILE”elseSTARTUP=“sh $STARTUPFILE”fibreakfidone 更证明了这一点。在这里脚本搜索用户目录$HOME下的.xsession或.Xsession脚本来执行。（在/etc/X11/Xsession.d目录下还有一些脚本，这里就不再分析了，各位有兴趣可以自己看看）另外来看看/etc/X11/xinit/xinitrc这个脚本，其原文内容如下： #!/bin/sh# $Xorg: xinitrc.cpp,v 1.3 2000/08/17 19:54:30 cpqbld Exp $# /etc/X11/xinit/xinitrc# global xinitrc file, used by all X sessions started by xinit (startx)# invoke global X session script. /etc/X11/Xsession 注意这一句“# global xinitrc file, used by allX sessions started by xinit(startx)”，这说明这个脚本只被xinit调用（即用户输入startx时）。而其执行的最后还是执行了/etc/X11/Xsession脚本。而用户如果用其它XWindow管理界面登录系统时这个脚本里的内容是不会被执行的。最后再来看看/etc/X11/xdm/Xsession这个脚本吧，其原文内容如下： #!/bin/sh# $Xorg: Xsession,v 1.4 2000/08/17 19:54:17 cpqbld Exp $# $XFree86: xc/programs/xdm/config/Xsession,v 1.3 2001/01/17 23:45:24 dawes Exp $# invoke global X session script. /etc/X11/Xsession 从内容来看，也是最终执行了/etc/X11/Xsession。再看看/etc/X11里面的目录结构： X Xsession.d cursors gdm rstart xinitXF86Config-4 Xsession.options default-display-manager lbxproxy sysconfig xkbXresources Xwrap