postinst is in fwupdate-signed 1.18+10-3.
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 | #!/bin/sh
set -e
case $1 in
    configure)
        /usr/lib/fwupdate/install
        ;;
esac
exit 0
 |