What does /etc/pam.d/* configuration from Linux

PAM expanses plugged authentication module

It's an powerful shared libraries used for dynamic authentication, and it was evolved from traditional PAM-Unix.

 here you can view your shared objects

#ldd /usr/sbin/sshd
or
#ldd /usr/sbin/sshd | grep libpam.so

here you can find the pam authentication libraries

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