dh_installnss(1)

Usage

dh_installnss [debhelper options]

Overview

dh_installnss is a debhelper program that is responsible for injecting NSS (Name Service Switch) services into /etc/nsswitch.conf.

Files

debian/package.nss

Lists the services to inject into /etc/nsswitch.conf when a package is configured and to remove when a package is removed or purged.

Each line in that file (a directive) should be of the form

db position service action condition

where the fields contain the following pieces of information:

db: The NSS database in which the service will be added. Usually "hosts".

position

Where to add the NSS service.

Possible values are "first", "last", "before=service", "after=service", plus the pseudo-positions "remove-only", "database-add" and "database-require".

The pseudo-position "remove-only" is used to mark services that are not going to be added during the installation of the package, but that will be removed during its deinstallation (e.g., legacy services).

The pseudo-position "database-add" is used to request the addition of a non-standard NSS database to /etc/nsswitch.conf during the installation of the package and its removal during the deinstallation of the package. When "database-add" is used, all other fields in the directive should be left empty.

The pseudo-position "database-require" is used to announce that one or more services in the nss file will be installed under a non-standard NSS database added by another package. When "database-require" is used, all other fields in the directive should be left empty.

service: The name of the NSS service to add.

action: Optional action specification "[STATE=ACTION]".

condition

Optional set of conditions to better define when a service should (or should not) be installed.

Only one kind of condition is currently defined: "skip-if-present=service,service,...".

Additionally, text between a "#" character and the end of line is ignored.

Examples

An example debian/nss file could look like this:

    hosts before=dns mdns4
    hosts before=mdns4 mdns4_minimal [NOTFOUND=return]
    hosts remove-only mdns    # In case the user manually added it

After the installation of this package, the original configuration of the hosts database in /etc/nsswitch.conf will change from:

    hosts:    files dns

to:

    hosts:    files mdns4_minimal [NOTFOUND=return] mdns4 dns

Caveats

Non-standard NSS databases

Directives in a package.nss file can reference a non-standard NSS database only if that database has been first declared with a "database-add" or "database-require" directive in the same file.

Non-standard NSS databases are all databases that are not defined in /etc/nsswitch.conf as shipped by the package base-files.

If a directive references an undeclared non-standard NSS database (e.g., "somedb"), dh_installnss will exit with the error message "Unknown NSS database 'somedb'".

A non-standard NSS database can be declared by at most one installed package. In other words, if the directives in the nss files of two packages A and B reference the same non-standard NSS database "somedb" and both packages can be installed at the same time, one of the following two solutions must be implemented:

1.: Package A supplies the "somedb database-add" directive, package B Pre-Depends on A and uses a "somedb database-require" directive.

2.: The shared package C supplies the "somedb database-add" directive, both package A and B Pre-Depend on C and use a "somedb database-require" directive.

Releases

Unchanged in 2 releases since Debian 12 (Bookworm).

12–13