How to enable auth details in FreeRADIUS log?

Here to describe how to enable detail auth information and authentication requests to the log file in FreeRADIUS.

FreeRADIUS 1.x:

Open and edit /etc/raddb/radiusd.conf to set:
log_auth = yes
auth_log
detail auth_log {
                detailfile = ${radacctdir}/%{Client-IP-Address}/auth-detail-%Y%m%d
                #
                #  This MUST be 0600, otherwise anyone can read
                #  the users passwords!
                detailperm = 0600
         }

FreeRADIUS 2.x:

Open and edit /etc/raddb/radiusd.conf to set:
auth = yes
Open and edit /etc/raddb/sites-available/default to set:
auth_log