postinst is in dpkg 1.16.1.2ubuntu7.
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 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 | #!/bin/sh -e
# This script can be called in the following ways:
#
# After the package was installed:
#	<postinst> configure <old-version>
#
#
# If prerm fails during upgrade or fails on failed upgrade:
#	<old-postinst> abort-upgrade <new-version>
#
# If prerm fails during removal:
#	<old-postinst> abort-remove
#
# If prerm fails during deconfiguration of a package:
#	<postinst> abort-deconfigure in-favour <new-package> <version>
#		   removing <old-package> <version>
#
# If prerm fails during replacement due to conflict:
#	<postinst> abort-remove in-favour <new-package> <version>
# Create the database files if they don't already exist
create_database() {
    admindir=${DPKG_ADMINDIR:-/var/lib/dpkg}
    for file in diversions statoverride status; do
	if [ ! -f "$admindir/$file" ]; then
	    touch "$admindir/$file"
	fi
    done
}
# Move the info directory from /usr/info to /usr/share/info
move_info_directory() {
    if [ -d /usr/info ] && [ ! -L /usr/info ] \
	&& [ -f /usr/info/dir ] && [ ! -L /usr/info/dir ]
    then
	echo "Moving /usr/info/dir to /usr/share/info/dir ..."
	mv /usr/info/dir /usr/share/info/dir
	if [ -f /usr/info/dir.old ]; then
	    mv /usr/info/dir.old /usr/share/info/dir.old
	fi
    fi
}
# Remove the /usr/info symlinks we used to generate
remove_info_symlink() {
    if [ -L /usr/info ]; then
	echo "Removing /usr/info symlink ..."
	rm /usr/info
    elif [ -L /usr/info/dir ]; then
	echo "Removing /usr/info/dir symlink ..."
	rm /usr/info/dir
    fi
}
# Create log file and set default permissions if possible
create_logfile() {
    logfile=/var/log/dpkg.log
    touch $logfile
    chmod 644 $logfile
    chown root:root $logfile 2>/dev/null || chown 0:0 $logfile
}
delete_multiarch_transitional_symlink() {
    if dpkg --compare-versions "$2" lt 1.16.0~ubuntu4 \
       && dpkg --compare-versions "$2" ge 1.16.0~ubuntu1; then
	# Remove the multiarch per-architecture symlink, which is
	# no longer used.
	infodir="/var/lib/dpkg/info/$(dpkg --print-architecture)"
	if [ -L "$infodir" ]; then
	    rm "$infodir"
	fi
    fi
}
case "$1" in
    configure)
	create_database
	create_logfile
	move_info_directory
	remove_info_symlink
	delete_multiarch_transitional_symlink "$@"
	;;
    abort-upgrade)
	delete_multiarch_transitional_symlink "$@"
	;;
    abort-deconfigure|abort-remove)
	;;
    *)
	echo "$0 called with unknown argument \`$1'" 1>&2
	exit 1
	;;
esac
exit 0
 |