config is in postgresql-common 173.
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 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 | #!/bin/bash
set -e
. /usr/share/debconf/confmodule
# If we have no versions, we do not need to worry about obsolete ones
if ! [ -d /usr/lib/postgresql ] || \
    [ ! -e /usr/share/postgresql-common/supported-versions ]; then
    db_stop
    exit 0
fi
# at some points we obsolete major versions within unstable; force the
# obsoletion notifications when upgrading over those
if dpkg --compare-versions "$2" lt-nl 71 2>/dev/null; then
    db_fset postgresql-common/obsolete-major seen false
fi
# determine versions
for v in `ls /usr/lib/postgresql/`; do
    # Ignore old libraries, etc.
    if [ -x /usr/lib/postgresql/$v/bin/psql ]; then
        AVAILABLE="$AVAILABLE $v"
    fi
done
SUPPORTED=`sh /usr/share/postgresql-common/supported-versions`
LATEST=`echo "$SUPPORTED" | sort -g | tail -1`
db_fget postgresql-common/obsolete-major seen || true
if [ "$RET" != "true" ]; then
    for v in $AVAILABLE; do
        unset sup
        for s in $SUPPORTED; do 
            if [ "$v" = "$s" ] || [[ "$v" > "$LATEST" ]]; then
                sup=1
                break
            fi
        done
        if [ "$sup" ]; then
            continue
        fi
        if dpkg -s "postgresql-client-$v" 2>/dev/null | grep -q ^Version: ; then
            db_fset postgresql-common/obsolete-major seen false
            db_subst postgresql-common/obsolete-major old $v
            db_subst postgresql-common/obsolete-major latest $LATEST
            db_input high postgresql-common/obsolete-major || true
            db_go || true
        fi
    done
fi
# createcluster.conf
db_input medium postgresql-common/ssl || true
db_go || true
db_stop
 |