An overview of the SSSD architecture
The SSSD consists of several processes, each of them has its own function. The SSSD processes can be one of the following:
1. the monitor - The purpose of the monitor process is to spawn the other processes, periodically ping them if to check if they are still running and respawn them if not. There...
Sometimes you'll need to setup a single point of authentification for e.g. to centralize stuff.
I've found a nice Document, about Integrating Linux systems with Active Directory using Open Source Tools from 2017.