preinst is in resolvconf 1.63ubuntu11.
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 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84  | #!/bin/sh
set -e
MYNAME=resolvconf.preinst
report() { echo "${MYNAME}: $*" ; }
report_err() { report "Error: $*" >&2 ; }
report_info() { report "$*" >&2 ; }
is_installed() {
	# Same function in preinst, postinst, postrm
	[ "$1" ] || return 1
	dpkg-query -W -f='${Status}\n' "$1" 2>/dev/null | grep -siq '^[[:alpha:]]\+ [[:alpha:]]\+ installed$' >/dev/null 2>&1
}
### Create run-time directories ###
#
# We create the run-time directories here, in the preinst, so that even if
# resolvconf is run before the postinst runs then there is nevertheless a
# place for resolvconf to store data.  (The latter can occur if resolvconf
# is installed simultaneously with a caching nameserver package whose
# postinst runs resolvconf to add its IP address.)
#
# The new standard location is /run;
# the old standard location was /lib/init/rw on Debian, /var/run/ on Ubuntu.
#
case "$1" in
  install|upgrade)
	# Ensure that /run/resolvconf/interface exists.
	mkdir -p /run/resolvconf/interface
	;;
  # abort-upgrade)
	# Don't do anything because we don't anything in the postrm on upgrade or on failed-upgrade
	# ;;
esac
### Prepare to notify already configured packages of our installation ###
case "$1" in
  install)
	# Create list of packages that might need to be notified of the installation of resolvconf
	if [ -d /usr/lib/resolvconf/dpkg-event.d ] ; then
		NOTIFICATION_HOOK_SCRIPTS="$(cd /usr/lib/resolvconf/dpkg-event.d >/dev/null ; run-parts --test .)"
		PACKAGES_TO_NOTIFY=""
		for SCRPT in $NOTIFICATION_HOOK_SCRIPTS ; do
			PKG="${SCRPT#./}"
			if is_installed "$PKG" ; then
				PACKAGES_TO_NOTIFY="${PACKAGES_TO_NOTIFY:+$PACKAGES_TO_NOTIFY }$PKG"
			fi
		done
		rm -f /run/resolvconf/packages-to-notify
		if [ "$PACKAGES_TO_NOTIFY" ] ; then
			echo "$PACKAGES_TO_NOTIFY" > /run/resolvconf/packages-to-notify
		fi
	fi
	;;
  # upgrade)
	# Don't do anything
	# ;;
  # abort-upgrade)
	# Don't do anything because we don't anything in the postrm on upgrade or on failed-upgrade
	# ;;
esac
# Automatically added by dh_installinit
if [ "$1" = install ] || [ "$1" = upgrade ]; then
	if [ -e "/etc/init.d/resolvconf" ] && [ ! -L "/etc/init.d/resolvconf" ]; then
		if [ "`md5sum \"/etc/init.d/resolvconf\" | sed -e \"s/ .*//\"`" != \
		     "`dpkg-query -W -f='${Conffiles}' resolvconf | sed -n -e \"\\\\' /etc/init.d/resolvconf '{s/ obsolete$//;s/.* //p}\"`" ]
		then
			echo "Obsolete conffile /etc/init.d/resolvconf has been modified by you, renaming to .dpkg-bak"
			mv -f "/etc/init.d/resolvconf" "/etc/init.d/resolvconf.dpkg-bak"
		else
			rm -f "/etc/init.d/resolvconf"
		fi
	fi
fi
# End automatically added section
exit 0
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