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fundamentals/pam.md

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+The Pluggabble Authentication Module controls minimum security requirements, such as password lengths.
+
+Configuration rests in `/etc/pam.d/common-password`, or sometimes `system-auth`.
+
+The file might be edited to contain:
+
+``` 
+
+password required pam_cracklib.so minlen=12 lcredit=1 
+ 
+ucredit=1 dcredit=2 ocredit=1 
+
+```
+ 
+This would enforce a minimum length of 12 characters for a password, one lowercase character, one upper case character, two digits, and one other (special) character.
+