### 28.2 The NSS Configuration File

Somehow the NSS code must be told about the wishes of the user. For this reason there is the file `/etc/nsswitch.conf`. For each database this file contain a specification how the lookup process should work. The file could look like this:

         # /etc/nsswitch.conf
         #
         # Name Service Switch configuration file.
         #

         passwd:     db files nis
         shadow:     files
         group:      db files nis

         hosts:      files nisplus nis dns
         networks:   nisplus [NOTFOUND=return] files

         ethers:     nisplus [NOTFOUND=return] db files
         protocols:  nisplus [NOTFOUND=return] db files
         rpc:        nisplus [NOTFOUND=return] db files
         services:   nisplus [NOTFOUND=return] db files

The first column is the database as you can guess from the table above. The rest of the line specifies how the lookup process works. Please note that you specify the way it works for each database individually. This cannot be done with the old way of a monolithic implementation.

The configuration specification for each database can contain two different items:

- the service specification like `files`, `db`, or `nis`.
- the reaction on lookup result like `[NOTFOUND=return]`.