The Name Service Switch (NSS) provides a mechanism for identifying sources of network information a computer should use, such as local password and group files, NIS maps, NIS+ tables, LDAP, and DNS, and the order in which these sources should be consulted when looking up users, groups, host names, and other information.
When you join a domain, the NSS configuration file, nsswitch.conf, is automatically updated to use the Centrify agent’s NSS module first. Using the adclient process and the service library, the Centrify NSS module accesses network information that’s stored in Active Directory through LDAP.
When a UNIX program or application needs to look up information, it checks the nsswitch.conf file and is directed to use the nss_centrifydc module. The nss_centrifydc module directs the request to Active Directory through the adclient process. The adclient process provides the information retrieved from Active Directory, then caches the information locally to ensure faster performance, reduce network traffic, and allow for disconnected operation.
Note: The order in which identity stores are listed in the nsswitch.conf file does not influence authentication. Authentication and authorization services are provided by Active Directory through the Centrify agent and its PAM service, so Active Directory is always tried before any other sources, regardless of what you have specified in the nsswitch.conf file. Instead, the nsswitch.conf file determines the sources to use in responding to NSS queries such as getpwnam. In general, you should not modify this file because modifying the file can compromise security and complicate auditing activity. In addition, you should not specify ldap as a source in any nsswitch.conf file where you have installed the Centrify agent. Specifying ldap in the nsswitch.conf file can cause the system to crash.