postinst is in libnss-gw-name 0.3-2.
This file is a maintainer script. It is executed when installing (*inst) or removing (*rm) the package.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63  | #!/bin/sh
set -e
# Automatically added by dh_makeshlibs
if [ "$1" = "configure" ]; then
	ldconfig
fi
# End automatically added section
if [ "$1" = "configure" ]; then 
	ldconfig
fi
# This code was taken from nss-mdns:
log() {
    echo "$*"
}
# try to insert gw_name entries to the "hosts" line in /etc/nsswitch.conf to
# automatically enable libnss-gw-name support; do not change the configuration if the
# "hosts" line already references some gw_name lookups
insert_nss_entry() {
    log "Checking NSS setup..."
    # abort if /etc/nsswitch.conf does not exist
    if ! [ -e /etc/nsswitch.conf ]; then
        log "Could not find /etc/nsswitch.conf."
        return
    fi
    perl -i -pe '
        sub insert {
            # this also splits on tab
            my @bits=split(" ", shift);
            # do not break configuration if the "hosts" line already references
            # gw_name
            if (grep { $_ eq "gw_name"} @bits) {
                return join " ", @bits;
            }
            # change "files" into "files gw_name"
            return join " ", map {
                $_ eq "files" ? ("$_","gw_name") : $_
            } @bits;
        }
        s/^(hosts:\s+)(.*)/$1.insert($2)/e;
    ' /etc/nsswitch.conf
}
action="$1"
if [ configure = "$action" ]; then
    if [ -z "$2" ]; then
        log "First installation detected..."
        # first install: setup the recommended configuration (unless
        # nsswitch.conf already contains gw_name entries)
        insert_nss_entry
    else
        # upgrade
        version="$2"
	
	# Nothing to do here yet
    fi
fi
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