After the installation program probes for hardware and maps the IDs to the appropriate kernel module (if available), the kernel module information is written to the /etc/ modprobe.conf file so it can be used on subsequent boots.
But, what should you do if a device is not configured by the installation program? You can use tools to probe the hardware and discover information that can be used to manually configure the device. This section discusses two tools for this purpose: Kudzu and ddcprobe.
Detecting Hardware with Kudzu
What happens when you add a new device after installation? The Kudzu program runs each time the system boots and performs a hardware probe. If new hardware is found, Kudzu attempts to map it to a kernel module. If successful, the information is saved, and the device is configured.
The Kudzu program includes an initialization script, /etc/rc.d/init.d/kudzu, which is run at boot time (unless disabled). A list of configured hardware for the system is stored in /etc/sysconfig/hwconf, a file maintained by Kudzu. If Kudzu finds new hardware not in this file, it prompts the administrator to configure it. If Kudzu detects removed hardware, it prompts the administrator to remove the configuration. If the administrator confirms the removal, it is removed from the hwconf file as well.
Instead of reading /etc/sysconfig/hwconf, issue the kudzu --probe command to view the list of hardware detected by Kudzu. To narrow down the results, you can also specify the bus or class:
kudzu --probe --bus=<BUS>
kudzu --probe --class=<CLASS>
For example, kudzu --probe --bus=PCI only displays the device on the PCI bus. Or, the command kudzu --probe --class=VIDEO only displays the video devices as demon strated.
Kudzu Probe for a Video Device
desc: “nVidia Corporation G70 [GeForce 7600 GT]”
If new hardware is detected, Kudzu references the hardware lookup tables in the /usr/share/hwdata/ directory installed by the hwdata software package and tries to map the hardware ID to a kernel module. If a driver is found, a configuration line for the hardware is added to the /etc/modprobe.conf so the same driver can be used on subsequent boots.
Kudzu does have a small configuration file /etc/sysconfig/kudzu with one option: SAFE. By default, SAFE is set to no. Set it to yes to enable the safe probe mode. The safe probe mode disables serial port, DDC monitor, and PS/2 probing.
If a kernel module is not available for an added piece of hardware, try updating the kernel and the hwdata RPM package. Support may have been recently added for the hardware.
Detecting Hardware with ddcprobe
Kudzu runs at boot time to detect and configure new hardware, including video cards. But, what if you suspect that Kudzu was unable to properly detect the video card or monitor in your system?
To view the video card and monitor information found by Kudzu, use the ddcprobe command. You must be root to run this command. Provided by the rhpxl package, ddcprobe is a script written to call the Kudzu’s probing function and display the results in a user-friendly output. If the rhpxl package is not installed, install it via Red Hat Network.
Along with the manufacturer and product name of the video card and monitor, ddcprobe displays information such as the amount of memory the video card has and the monitor refresh rates.
Video Card Probe Results
Videocard DDC probe results
Description: Intel Corporation Intel(r)865G Graphics Controller
Memory (MB): 15
Monitor DDC probe results
Name: Dell 1702FP (Analog)
Horizontal Sync (kHZ): 30-80
Vertical Sync (HZ) : 56-76
Width (mm): 340
If the ddcprobe output is not correct for the monitor or video card, run the system-config-display utility by selecting the System menu from the top panel of the desktop and then selecting Administration, Display or by executing the system-config-display command. You must enter the root password to proceed if you are not already root when you run the program. Manually select the correct monitor or video card so that the correct settings are written to the configuration file.