etcnsswitchconf

etcnsswitchconf refers to the configuration used by the Name Service Switch (NSS) on Unix-like systems, most commonly the file /etc/nsswitch.conf. This file instructs the system how to resolve various databases, such as user accounts, hostnames, and other networked resources, by defining the order and sources to consult.

The file consists of lines that pair a database name with an ordered list of sources. Each line follows the format: database: source1 source2 ... The sources indicate where to look for information, and common options include files (for local files like /etc/passwd and /etc/group), dns (domain name system), ldap (Lightweight Directory Access Protocol), nis (Network Information Service), sss (System Security Services Daemon), and mdns (multicast DNS), among others. The syntax also supports compatibility and conditional behavior, such as the use of compat for legacy /etc/passwd and /etc/group formats or [NOTFOUND=return] to alter lookup flow when a source cannot resolve an entry.

Common databases configured in nsswitch.conf include passwd, group, and shadow for user information; hosts for hostname resolution; and services, protocols, networks, and ethers for related network data. A typical line might read: passwd: files ldap, group: files ldap, hosts: files dns mdns4_minimal [NOTFOUND=return] dns. On some systems you may also see lines using sss or nis, reflecting local deployment choices or centralized authentication.

Utilities such as getent query the NSS databases defined in this file. NSS caching daemons like nscd or sssd may cache results and improve performance without altering the configuration. Editing etcnsswitchconf requires appropriate privileges and should be done with care, as misconfigurations can affect system authentication and name resolution.