12-30-2009 12:36 AM
i have recently install rhel 4 found can not get display,
would like to know which demon is use for display, what logs we can check for display, how to troubleshoot.
thanks in advance.
12-30-2009 02:13 AM
The text console mode is managed by the kernel directly. If you can connect to the system remotely, run the "dmesg" command to view the recent kernel messages (sometimes all kernel messages since the system was rebooted).
The graphical user interface uses the X Window System version 11, or X11 for short.
In X11, all GUI-type programs will use a common set of X11 libraries (located in /usr/X11R6/lib or ...lib64 directory on RHEL4).
These libraries will establish a connection to the "X server" process that manages a display, keyboard and mouse. The X server may be either local or remote: the environment variable DISPLAY will indicate where to connect to find the X server.
If DISPLAY does not contain a hostname or IP address, but instead just something that begins with a colon (usually ":0.0"), it means the display is local and the application should use a filesystem socket in /tmp/.X11-unix to access it.
If DISPLAY contains a hostname or an IP address (e.g. "192.168.1.23:0.0"), then the X server is considered to be remote and the application will use a network connection to access it. This will be a completely insecure connection, with no encryption at all. The protocol used is TCP, and the port number is (the first number after the colon + 6000).
A Windows workstation cannot receive an X11 protocol connection on its own, because the X11 protocol is not the same as the Windows remote desktop protocol. This is why you must run a special X server application on a Windows workstation if you want to use it to remote access GUI programs on Linux/Unix systems. This X server application may be a commercial like ReflectionX, or a free one like Xming.
The X server is not really a daemon, because its very purpose is to interact with the user. The X server is always located where the physical display is, and many server machines run just fine with no local X server at all: the only X server required is in the sysadmin's workstation.
If you're running a local GUI display on Linux, the local X server is /usr/X11R6/bin/X or /usr/bin/X (depends on distribution). The X server log is typically written to /var/log/Xorg.0.log.
The X server configuration file is /etc/X11/xorg.conf. In RedHat, there is a tool named "system-config-display" that tries to autoconfigure the display for you and/or present a friendly text-based UI for manual configuration.
Most Linux distributions will completely disable the network connectivity on their local X server by starting it with the "-nolisten tcp" option by default. You can then use SSH with its "secure X11 forwarding" feature to get remote X11 access: it is actually much easier than the traditional way to set up remote X11 connections, because SSH handles all the necessary details for you.
(The DISPLAY variable will be set automatically for any SSH session that has secure X11 forwarding enabled, and you don't need "xhost +" command because SSH will set up the proper xauth keys for you.)
In a Linux system, the X server is often started by a "X display manager" process. This process may be xdm, kdm, gdm or something else, depending on the chosen desktop environment (kdm is the default for KDE, gdm for Gnome, xdm or others for anything else). The log for such a display manager process is named like /var/log/?dm.log.
So... I hope this helps?
Please describe your problem in more detail?
12-31-2009 01:39 AM
Some displays take a while to initialise and if your system boots very quickly you may not have the time to see the boot messages. Another thing is to try booting from a Linux CD/DVD and see if you get a display.