postrm is in iptables-optimizer 0.9.13-2.
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  | #!/bin/sh -e
# Remove cached config files on purge only
case "$1" in
    purge)
	rm -rf /var/cache/iptables-optimizer
	rm -f  /var/run/iptables-optimizer-*
    ;;
    remove|upgrade|failed-upgrade|abort-install|abort-upgrade|disappear)
        # Nothing to do here
    ;;
    *)
        echo "$0 called with unknown argument \`$1'" >&2
        exit 1
    ;;
esac
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