I've just migrated to a new server (ubuntu 12.04.4) and a few things are a little different due to updated software. One problem I had was that SMTP wasn't working. It was trying to authorise using PAM and expected to find the modules (in this case pam_mysql.so) in /lib/security. The installation had actually placed these modules in /lib/x86_64-linux-gnu/security so to get things going, I just copied them to /lib/security and all started working as it should. I then thought a better solution would be to create /lib/security as a symlink to the actual folder so in /lib created (having removed the original security!) However that didn't work and I had to go back to my original method. So my questions... why didn't it work? would it have worked if I'd created the /lib/security directory and then added symlinks to each of the files individually (or even hard links)? what is the best way to achieve what I want, i.e. reference the actual files rather than duplicate them? I know I could alter the config files in /etc/pam.d and specify the path name but that seems like rather a lot of unnecessary work which could need changing again if the files get updated and installed elsewhere!