Linux – nsswitch.conf: is there a daemon I need to restart

I think the answer to your problem is in this this line:

open("/etc/nss-pgsql-root.conf", O_RDONLY) = -1 EACCES (Permission denied)

Try relaxing permissions on this file to be readable by "group" and "other" and see if that solves the problem.

You are wrong that the file corresponds to /etc/shadow. It corresponds to /etc/password, which is readable by "group" and "other". Your PostgreSQL database and tables used for authentication correspond to /etc/shadow.

It can't connect to the database because it can't read the database access credentials from this file.

The nss-pam-ldapd package allows LDAP directory servers to be used as a primary source of name service information. When I would run 'getent passwd', I would only see the users from the /etc/passwd file. When I started the /etc/init.d/nslcd service and then issued the 'getent passwd' command, I then saw all LDAP users and system users and the shells were synced.

The service did not start when I installed the nss-pam-ldapd package, I manually started it, and now everything works like a charm.

Also the order of the /etc/nsswitch.conf was very important:

 passwd:     files ldap sss   
 shadow:     files ldap sss   
 group:      files sss