/lib/udev/rules.d/95-dm-notify.rules is in dmsetup 2:1.02.145-4.1ubuntu3.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 | # Copyright (C) 2009 Red Hat, Inc. All rights reserved.
#
# This file is part of LVM2.
# Udev rules for device-mapper devices.
#
# These rules are responsible for sending a notification to a process
# waiting for completion of udev rules. The process is identified by
# a cookie value sent within "change" and "remove" events (the cookie
# value is set before by that process for every action requested).
ENV{DM_COOKIE}=="?*", RUN+="/sbin/dmsetup udevcomplete $env{DM_COOKIE}"
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