#
# Linux PAM  (Linux is not the same Linux)
#

Not all modules are available in all distributions!

Configuration directories:  ( rpm -q --filesbypkg pam,
                                            dpkg-query -S libpam0g,
                                           dpkg-query -S libpam-modules )
/etc/pam.d/
/etc/security/

Modul Directories:    ( find / -type d -name security,
                                    find / -type f -name libpam.so*
                                    will find the directory and subdirectory
                                    'security' of pam-modules )

Oracle Linux6:
/lib64/
/lib64/security/
Oracle Linux7:
/usr/lib64/
/usr/lib64/security/
Centos7:
/usr/lib64/
/usr/lib64/security/
Debian9:
/lib/x86_64-linux-gnu/
/lib/x86_64-linux-gnu/security/
Debian11:
/usr/lib/x86_64-linux-gnu/
/usr/lib/x86_64-linux-gnu/security/
ubuntu 20.4:
/usr/lib/x86_64-linux-gnu/
/usr/lib/x86_64-linux-gnu/security/
openSUSE 12.2:
/lib64/
/lib64/security/
openSUSE 15.3:
/lib64/
/lib64/security/

Compatiblety in /etc/pam.d :
# 'common-account' in debian is not the same as 'common-account' in openSUSE or in Ubuntu !!!

Only Centos 7 has preconfigured settings for 'pam_pwquality'
password-auth-ac:
   password    requisite     pam_pwquality.so try_first_pass local_users_only retry=3 authtok_type=
system-auth-ac:
   password    requisite     pam_pwquality.so try_first_pass local_users_only retry=3 authtok_type=

# Further settings must set manually.

# CentOS has a tool 'authconfig' to configure PAM.

# Debian and Ubuntu has a tool  'pam-auth-update' that writes PAM configuration files for you.

# openSUSE has a command 'pam-config' for configuring pam (examples):
   add debugging:            pam-config -a pam-debug
   delete debugging:         pam-config -d pam-debug
   add password length:   pam-config -a cracklib-minlen=12
# use  'pam-config --list modules'  to see all supported modules,
# not all installable modules are supported !!!

# 'PAM Mastery by Michael W Lucas' is the remarkable book / tutorial.
# ISBN-13: 978-1537657707
# ISBN-10: 1537657704