# Pluggable Authentication Modules

Authentication of users in ThinLinc is performed using the Pluggable Authentication Modules (PAM). This means ThinLinc can authenticate users using any system for which there is a PAM module. Examples of PAM modules include pam_ldap for accessing LDAP directories, and pam_sss for authenticating via SSSD. Of course, authentication using the standard plaintext password files of Linux is also possible using the PAM module pam_unix.

## Configuration files for PAM

PAM is configured by editing the files located in the directory `/etc/pam.d/`.

Different Linux distributions have slightly different ways of configuring PAM. The ThinLinc installation program will set up ThinLinc to authenticate using the same PAM setup as the Secure Shell Daemon, by creating a symbolic link from `/etc/pam.d/thinlinc` to either `/etc/pam.d/sshd` or `/etc/pam.d/remote`, depending on which of the latter files that exists at installation. This will work on most distributions. Be aware that the PAM settings for the Secure Shell Daemon might really be somewhere else. For example, on Red Hat distributions, the file `/etc/pam.d/system-auth` is included by all other PAM files, so in most cases, that is the file that should be modified instead of the file used by sshd.