postinst is in kpartx-boot 0.4.9-3ubuntu7.
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 | #!/bin/sh
# postinst script for kpartx-boot
#
# see: dh_installdeb(1)
set -e
# Source debconf library.
. /usr/share/debconf/confmodule
case "$1" in
    configure)
	if [ -x /usr/sbin/update-initramfs -a -e /etc/initramfs-tools/initramfs.conf ]; then
		update-initramfs -u
	fi
    ;;
    abort-upgrade|abort-remove|abort-deconfigure)
    ;;
    *)
        echo "postinst called with unknown argument \`$1'" >&2
        exit 1
    ;;
esac
# dh_installdeb will replace this with shell code automatically
# generated by other debhelper scripts.
exit 0
 |