PAM uses arguments to pass information to a pluggable module during authentication for some modules.
For example, the pam_userdb.so module uses information stored in a Berkeley DB file to authenticate the user. Berkeley DB is an open source database system embedded in many applications. The module takes a db argument so that Berkeley DB knows which database to use for the requested service.
The following is a typical pam_userdb.so line in a PAM configuration. The <path-to-file> is the full path to the Berkeley DB database file:
auth required pam_userdb.so db=<path-to-file>
Invalid arguments are generally ignored and do not otherwise affect the success or failure of the PAM module. Some modules, however, may fail on invalid arguments. Most modules report errors to the /var/log/secure file.