postinst is in postgresql-10 10.6-0ubuntu0.18.04.1.
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 | #!/bin/sh
set -e
VERSION=${DPKG_MAINTSCRIPT_PACKAGE##*-}
if [ "$1" = configure ]; then
. /usr/share/postgresql-common/maintscripts-functions
configure_version $VERSION "$2"
fi
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