how to get log files?

I have some problems with the installation of S870, which is, every time I start the PC, it will go black before I can log into the system(rhel 4.x), so I want to view the log file and figure out the problem. Then I disconnect S870 with my workstation so that my system start normally. But in the X log file, I cannot detect the error message in it. So I guess when I start the X window, the older log file which contains error messages are replaced with the latest and normal log informations.
So, how can I get the useful log file which can help me to solve the problem? And I have seen “nvidia_bug_report.log” many times in the forum. But I cannot find any such log files in /var/log, so, is it a log file which only will be generated after a cuda program failed?
Thanks a lot!!!

nvidia_bug_report.log is generated by running a nvidia script. What I would do is switch to a terminal after the screen has gone black (Ctrl+Alt+F1 e.g.), login as root and then your can watch the logfiles.

You can then also do telinit 3 to go to terminal mode and run startx to see the errors appear onscreen. (all this works on redhat/fedora, I don’t know about other distros)