Learning the KDE Display Manager
If you install only the KDE desktop or define the DISPLAYMANAGER variable in the /etc/sysconfig/desktop file as KDE, the kdm program starts the X server for the local display and displays the graphical login window through which you log in to the system. Figure 9-3 shows the graphical login screen that you see when you run the kdm display manager. (To change to the KDE display manager, just add the line DISPLAY-MANAGER="KDE" to the /etc/sysconfig/desktop file.)
- Figure 9-3: Graphical Login Screen Managed by kdm.
When kdm runs, it reads various configuration parameters from the configuration file /usr/share/config/kdm/kdmrc, which has a structure similar to a Windows INI file. For example, here is a typical kdmrc file (shown without most of the comment lines that begin with #):
[Desktop0]
# Background of the greeter - - the login window
BackgroundMode=VerticalGradient
BlendBalance=100
BlendMode=NoBlending
ChangeInterval=60
Color1=138,148,198
Color2=104,112,150
CurrentWallpaper=0
LastChange=0
MinOptimizationDepth=1
MultiWallpaperMode=NoMulti
Pattern=
Program=
UseSHM=false
ReverseBlending=false
Wallpaper=/usr/share/backgrounds/images/default.png
WallpaperList=
WallpaperMode=Centred
[General]
Xservers=/usr/share/config/kdm/Xservers PidFile=/var/run/kdm.pid
[Xdmcp] Enable=false
Xaccess=/usr/share/config/kdm/Xaccess Willing=/usr/share/config/kdm/Xwilling
[Shutdown]
HaltCmd=/sbin/poweroff [X-*-Core]
# Core config for all displays Resources=/etc/X11/Xresources Setup=/usr/share/config/kdm/Xsetup Startup=/usr/share/config/kdm/Xstartup Reset=/usr/share/config/kdm/Xreset Session=/usr/share/config/kdm/Xsession SessionsDirs=/usr/share/xsessions AutoReLogin=false AllowRootLogin=true AllowNullPasswd=true AllowShutdown=Root
# Greeter config for all displays SessionTypes=default,kde,failsafe,gnome GUIStyle=Bluecurve
LogoArea=Clock
AntiAliasing=true
UserList=false
HiddenUsers=adm,alias,amanda,apache,bin,bind,daemon,exim, falken,ftp,games,gdm,gopher,halt,httpd,ident,ingres,kmem,lp,mail,mailnull,m an,mta,mysql,named,news,nfsnobody,nobody,nscd,ntp,operator, pcap,pop,postfix,postgres,qmaild,qmaill,qmailp,qmailq, qmailr,qmails,radvd,reboot,rpc,rpcuser,rpm,sendmail,shutdown, squid,sympa,sync,tty,uucp,xfs,xten
MinShowUID=500
SortUsers=true
PreselectUser=None
FocusPasswd=false
EchoMode=OneStar
# Core configurations for local displays
# place local display core configurations here AllowShutdown=All
AllowRootLogin=false AllowNullPasswd=true
# Greeter configurations for local displays
LoginMode=DefaultLocal
AllowClose=false
As you can see, the file is organized into sections, with each section identified by labels within square brackets. Each section specifies a related set of options that affects some aspect of the GUI login process.
You can configure the look and feel of the kdm greeter—the login dialog box—on each X display individually. The configuration of each display is specified by a section name that has the following format:
[X-host:number_class-subsection]
where host refers to the host name of the system to which the display is attached (can be empty for a local display), number is the display number (0, if you have only one display), class is a display class (it's optional and ignored in most cases), and subsection identifies the element of the display manager to which the options apply. For example, if the options apply to the desktop, subsection is Desktop. If the options are for the greeter, the subsection is Greeter. You can use an asterisk (*) for any of these elements —host, number, and class —as a wildcard.
Thus, to specify the options for the greeter for all displays, place the options in a section named [X-*-Greeter]. To change some of these greeter options for the local displays, place the changed options in the [X-:*-Greeter] section. On the other hand, if you want to customize some aspect of the greeter for the first local display (which is display number 0), place those options in the section labeled [X-:0-Greeter].
Table 9-2 summarizes some common kdm configuration options, organized by sections. I show the X display options for all displays. To customize these for a specific display, you can add a section with a name that reflects the X display to which the options apply.
Table 9-2: Common kdm Configuration Options
Configuration Option Description
[General] section
LockPidFile=true or false If set to true, kdm locks the PidFile to prevent multiple instances of kdm from running simultaneously.
PidFile = /var/run/kdm.pid File where kdm should store its process ID (ID).
Xservers= /usr/share/ File containing list of X servers to start (one per display).
config/kdm/Xservers
Table 9-2 (continued)
Configuration Option
Description
[Xdmcp] section
ChoiceTimeout=seconds
Enable=true or false
Port=177
RemoveDomainname= true or false
SourceAddress=true or false
Willing= /usr/share/ config/kdm/Xwilling
[Shutdown] section
Number of seconds to wait for display to respond after the user has selected a host from the chooser (default is 15 seconds).
If set to true, kdm listens on port 177 and supports the X Display Manager Control Protocol (XDMCP) that enables users to log in to other hosts on the network (the default is true).
The UDP port number where kdm listens for XDMCP requests (default is 177).
If set to true, strips domain name from remote display names if it is equal to the local domain (default is true).
Use the numeric IP address of the incoming connection instead of the host name (useful on multihomed hosts, the default is false).
Program to run to generate replies to XDMCP BroadcastQuery requests (the Xwilling program is a shell script that displays the number of users and current load average).
HaltCmd=/sbin/poweroff RebootCmd=/sbin/reboot
Full pathname of command to run to halt the system.
Full pathname of command to run to reboot the system (default is /sbin/reboot).
[X-*-Core] section (core configuration for all displays)
AllowNullPasswd= true or false
If set to true, kdm allows users with empty passwords to log in (default is true).
AllowRootLogin=true or false If set to true, kdm allows logins by root (default is true).
AllowSdForceNow=Root or Al
AllowShutdown = Root or Al
AutoReLogin = true or false
DefaultSdMode=ForceNow or TryNow or Schedule
Specifies who can abort all currently running programs when shutting down system; choices are All for anyone or Root for root user (default is All).
Specifies who can shut down the system; possible values are All to enable anyone to shut down the system, None to prevent shutdown from the login screen, and Root to require root password for shutdown (default is All).
If set to true, kdm automatically restarts a session after the X server crashes or if it is killed by pressing Ctrl-Alt-Backspace (default is false)
The default mode for shutdown; choices are ForceNow to shut down immediately, Schedule to shut down after the session exits, or TryNow to shut down if no session is open and do nothing otherwise (default is Schedule).
Configuration Option
Description
[X-*-Core] section (core configuration for all displays)
OpenDelay=seconds OpenRepeat=seconds OpenTimeout=seconds PingInterval=seconds
Reset=/usr/share/config/ kdm/Xreset
ResetSignal=1
Session= /usr/share/ config/kdm/Xsession
SessSaveFile=.wmrc
Setup= usr/share/ config/kdm/Xsetup
StartAttempts=number
StartInterval=seconds
Startup= usr/share/ config/kdm/Xstartup
TerminateServer= true or false
Number of seconds to wait before retrying to open the display after any error (default is 15 seconds).
Number of seconds to wait before trying to open display again (default is 5 seconds).
Number of seconds to wait before timing out on the attempt to open the display (default is 120 seconds).
Number of minutes between successive pinging of remote displays (ping checks if network connection is up and running; default interval is 5 minutes).
Program to run after a user session ends.
The signal to send to reset the local X server (default is 1, which stands for SIGHUP).
Program that accepts the SessionTypes argument and starts an appropriate session.
Filename (in user's home directory) where the last session type is stored (default is .wmrc).
Program to run before showing the greeter window.
The maximum number of times to try opening a display before the display is disabled (default is 4).
Number of seconds to wait before resetting the StartAttempts counter (default is 30 seconds).
Program to run before starting a user session.
If set to true, restarts the local X server instead of resetting after session ends (default is false).
TermSignal=signum [X-*-Greeter] section (greeter configuration for all displays)
The signal to send to terminate the local X server (default is 15, which stands for SIGTERM).
AntiAliasing=true or false
DefaultUser=username
EchoMode=OneStar or ThreeStar or NoEcho
If set to true, fonts shown in the greeter should be antialiased (default is false).
User preselected for login if PreselectUser=Default.
What to show as user types the password; choices are NoEcho to show nothing at all, OneStar to show a * for each letter typed, or ThreeStars to show *** for each letter typed (default is OneStar).
Font used for the "Login Failed" message.
Table 9-2 (continued)
Configuration Option
Description
[X-*-Greeter] section (greeter configuration for all displays)
FocusPasswd=true or false
GreeterPosFixed= true or false
GreeterPosX=pixels
GreeterPosY=pixels
GreetString= welcometext
GUIStyle=Bluecurve
HiddenUsers=user1,user2,
Language=en_US LogoArea=Clock
LogoPixmap= /usr/share/ apps/kdm/pics/kdelogo.png
MinShowUID=500
>JumLock=Off
If set to true, the password input line is automatically selected to receive the keyboard input (default is false)
If set to true, the position of the greeter window is fixed and specified by GreeterPosX and GreeterPosY (default is false).
Horizontal position, in pixels, of greeter window. Vertical position, in pixels, of greeter window. The font to use for the welcome text.
Welcome text in greeter window (default is "Welcome to %s at %n"); use following special character strings: %d = current display
%h = host name, possibly with domain name
%n = node name, most probably the host name without domain name
%s = operating system (Linux) %r = operating system's version %m = machine (hardware) type %% = a single %
The look and feel of the greeter (other choices are
Default, Windows, Motif, CDE, and any other styles installed on the system).
List of user names not to be listed in the greeter when
ShowUsers is NotHidden.
Language to use in the greeter (default is en_US).
What to show in the area to the right of the text input line (other options are Logo to display an image specified by LogoPixmap, Clock to display an analog clock, and None to display nothing).
The image to show when LogoArea is set to Logo.
Users with UID less than the specified number are not shown.
What to do with the Num Lock key during the time when the greeter is running; choices are On to turn it on, Off to turn it off, and Keep to leave it at its previous state.
Configuration Option Description
[X-*-Greeter] section (greeter configuration for all displays)
PreselectUser=None or User name to be preselected for login; choices are
Previous or Default Previous to preselect the previous user, Default to select user listed in DefaultUser field, or None to not preselect at all (default is None).
SelectedUsers = user1, List of users to show when ShowUsers=Selected.
SessionTypes= default.kde, Names of session types that the user can select from the failsafe.gnome GUI login window.
ShowUsers = None Which user names, along with pictures, to show in the greeter; choices are NotHidden to show all users except those listed in HiddenUsers, Selected to show only those users listed in SelectedUsers, and None to show no users at all (default is NotHidden).
SortUsers=true or false If set to true, sort user names alphabetically (default is true).
StdFont= Sans,10,-1,5,50, Normal font used in the greeter.
Using GNOME
GNOME stands for GNU Network Object Model Environment; and GNU, as you probably know, stands for GNU's Not Unix. GNOME is a GUI and a programming environment. From the user's perspective, GNOME is like the Motif-based Common Desktop Environment (CDE) or Microsoft Windows. Behind the scenes, GNOME has many features that enable programmers to write graphical applications that work together well. The next few sections provide a quick overview of GNOME, highlighting the key features of the GNOME GUI. You can explore the details on your own.
You can always find out the latest information about GNOME by visiting the GNOME home page at www.gnome.org.
Continue reading here: Taking Stock of GNOME
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