Looking for logging into the Linux Authentication site and are not getting the correct working link for it? In such a case, you can use the links given here by searching your desired login page in the search box. If the page is present on our website then you will get all the links related to the Linux Authentication site. After that you can login as usual with your login credentials.
http://en.tldp.org/HOWTO/pdf/User-Authentication-HOWTO.pdf
https://unix.stackexchange.com/questions/15455/login-and-su-internals
https://community.hortonworks.com/articles/175098/authentication-and-authorization-on-linux-os.html
http://www.linuxgeek.net/documentation/authentication.phtml
https://www.oreilly.com/library/view/linux-server-hacks/0596100825/ch01.html
https://www.howtoforge.com/linux_ldap_authentication
https://www.linux.com/learn/how-set-2-factor-authentication-login-and-sudo
https://linuxconfig.org/linux-authentication-login-with-usb-device
https://www.computerhope.com/unix/ulogin.htm
https://www.digitalocean.com/community/tutorials/how-to-set-up-centralized-linux-authentication-with-freeipa-on-centos-7
https://www.techrepublic.com/article/how-to-setup-two-factor-authentication-in-linux/