NsSwitch.Conf

The Name Service Switch configuration file (or nsswitch.conf(5)), typically found at /etc/nsswitch.conf, declares how domain names should be translated into IP addresses.

Example

passwd:         compat
group:          compat
shadow:         compat
hosts:          dns [!UNAVAIL=return] files
networks:       nis [NOTFOUND=return] files
ethers:         nis [NOTFOUND=return] files
protocols:      nis [NOTFOUND=return] files
rpc:            nis [NOTFOUND=return] files
services:       nis [NOTFOUND=return] files

Syntax

Databases

The first column (delimited by spaces or tab characters) indicates a database, while every subsequent column is a service specification or optional action.

Service Specifications

Common service specifications are:

• files (i.e. /etc/hosts)

• dns (i.e. runtime lookups based on /etc/resolv.conf)

• myhostname (see nss-myhostname(8))

• mymachine which connects to systemd-machined (see nss-mymachines(8))

• resolve which connects to systemd-resolved (see nss-resolve(8))

Optional Actions

Option actions follow the pattern of [STATUS=ACTION] and [!STATUS=ACTION].

A status can be any of:

• success meaning 'no error'.

• notfound meaning 'error in lookup'.

• unavail indicates a connection couldn't be made.

• tryagain indicates 'temporarily unavailability', as with locked connections.

An action can be any of:

• return meaning 'return the result'

• continue meaning 'try the next item'

• merge causes the system to try both the preceding and the following items

By default, only a success status results in a return action. Anything else will result in a continue. The exception the group database, where a notfound status will lead to a continue action regardless of any action specified.

See also

nsswitch.conf(5)

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