while hardening a red hat enterprise 5 installation I have done something that causes the sessions of all user accounts except root to close immediately after authentication. in the /var/log/secure log file it will show three log entries per attempt:

<date/time><hostname> login: pam_unix(login:session): session opened for user fred by LOGIN(uid=0)

<date/time><hostname> login: LOGIN ON tty1 BY fred

<date/time><hostname> login: pam_unix(login:session): session closed for user fred

Since I did a number of things and have not been able to identify what caused this I am hoping that someone might have an idea of where I can look for possible culprits.

Login as root and check to see if you have adequate disk space remaining on all your partitions. I had this problem on a hardened gentoo box, the home partition filled up denying logins for everyone else but root.

Unfortunately, or fortunately I do have plenty of room on all of my partitions. Thanks for the suggestion though.