We're running a small Centos 5 server in a virtual machine for a class assignment. For reasons unknown, starting about a week ago a number of services started failing. When we tried to investigate we discovered that we could no longer login as root. We booted into single user mode and reset the root password, but even after doing so, still got an error message of "Login incorrect" when logging in. We can login in as other users. At first we were not able to run the command su root. We would recieve the error message "cannot set groups operation not permitted." However we resolved that error by running the command chmod u+s /bin/su in single user mode. We still cannot log directly into root.
Any thoughts on how to get root access back. It's problematic because we still can't get some services like ssh running with the setup we've got. The screen also locks up whenever we try to boot into the gui with run level 5, instead of the command line with level 3