postrm is in solr-tomcat 3.6.2+dfsg-11.
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 | #!/bin/sh
set -e
case "$1" in
    remove)
        rm -f /etc/tomcat8/policy.d/05solr.policy
    	if [ -x invoke-rc.d ]; then
    	    invoke-rc.d tomcat8 restart || true
    	fi
    ;;
    upgrade|purge|failed-upgrade|abort-install|abort-upgrade|disappear)
	    # do nothing
    ;;
    *)
        echo "postrm called with unknown argument \`$1'" >&2
        exit 1
    ;;
esac
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