install libpam-radius-auth
apt-get install libpam-radius-auth
open /etc/pam_radius_auth.conf
nano /etc/pam_radius_auth.conf
and add the following lines into it. Your_IP and PORT are the IP address and Port of Radius sever. SecretKey is the Secret of radius server. 3 is the timeout in seconds.
# server[:port] shared_secret timeout (s) YOUR_IP:PORT SecretKey 3
Change the permissions :
chown root /etc/pam_radius_auth.conf chmod go-rwx /etc/pam_radius_auth.conf
open /etc/pam.d/common-auth :
nano /etc/pam.d/common-auth
and add the following lines :
auth sufficient pam_radius_auth.so