Red Hat Enterprise Linux 5 Administration Unleashed

528APPENDIX AInstalling Proprietary Kernel Modules12. Now, you can restart the X server and start using the nVidia display driver. Executethe init 5 command as root to start the graphical login screen.To verify that the driver is being used, execute the following command:lsmod | grep nvidiaYou should see a line similar to the following if the kernel module is loaded:nvidia 5698648 22Recognizing a Tainted KernelThe license of a particular kernel module can be determined with the following command:modinfo | grep licenseFor example, the following output shows that the module is written under the GPL:license:GPLThe following shows the output from the modinfo nvidia | grep license for the nVidiadisplay driver, which is distributed under the nVidia license:license:NVIDIAIf a proprietary kernel is loaded when a kernel crash occurs, it is very difficult to debugthe problem because the source code is not available. For this reason, a mechanism wasadded to the kernel to allow developers and users to determine whether proprietarymodules are loaded. When a kernel module is loaded, the kernel checks for a macro calledMODULE_LICENSE. If the license is not an approved open source license such as the GPL,the kernel is flagged as “tainted.”How can you determine whether the kernel is tainted? The /sbin/lsmod command liststhe currently loaded modules. If you pipe it through less, you can read the header:/sbin/lsmod | lessIf you see the phrase Tainted: P at the end of the header, proprietary kernel modules areloaded:Module Size Used by Tainted: PIf the kernel crashes while a proprietary module is loaded, try reproducing the crashwithout the kernel module loaded. If the problem goes away, chances are that the moduleitself is causing the crash. If the problem still occurs with an untainted kernel, theproblem is likely in either the kernel or another kernel module.