SSSD couldn’t load the configuration database : No such file or directory
You may encounter this issue when you upgrade from Ubuntu 16.04 to Ubuntu 18.04, or upgrading through any Ubuntu versions. The SSSD service might not start. Most probably you might be missing the configuration file
You can check if that configuration file exists.Try this if the file is missing:
$ sudo cp /usr/lib/x86_64-linux-gnu/sssd/conf/sssd.conf /etc/sssd/
$ sudo chmod 600 /etc/sssd/sssd.conf
$ sudo systemctl restart sssd.service
Kindly comment below if it works for you.