linux debian - logging as another user throws "Module is unknown"

>Environment
Debian 7 - amd64.



>Problem:
Attempt to login as another user throws the following error message:
  Module is unknown


 >Solution
 


Three possibilities:
- pam configuration
- pam module not installed
- pam module corrupted

Try to fix the most simple first: pam configuration, then follow the order suggested.





1. PAM CONFIGURATION:

- As root, edit the file:
su
scite /etc/pam.d/login &

- Comment the following line
session    required   pam_limits.so
- becomes:
#session    required   pam_limits.so

If you have a local oracle instance, for testing purpose and security is not a issue, comment also the lines below if you have oracle's concerned issues:


#oracle 11g install from rin201
session required /lib/security/pam_limits.so       
session required pam_limits.so

- becoming:
#oracle 11g install from rin201
#session required /lib/security/pam_limits.so       
#session required pam_limits.so

- Try again to log as another user, for instance:

  sudo login postgres

- If it fails, check pam installation.



2. INSTALLING PAM MODULES

NOTE: if you're not sure if pam is installed, you can install it.
There is no problem since if it is already installed, the apt-get will return a message telling you so.


- check the package name
dpkg --search pam

- install the following:
apt-get install libpam-modules
apt-get install libpam-runtime


3. TO REINSTALL PAM




aptitude reinstall libpam-modules



SEE ALSO:
http://www.linuxquestions.org/questions/linux-general-1/failing-at-chroot-101-a-758547/#post3705048