lvm2/udev/10-dm.rules.in

# Udev rules for device-mapper devices.
#
# These rules create a DM control node in /dev/(DM_DIR) directory.
# The rules also create nodes named dm-x (x is a number) in /dev
# directory and symlinks to these nodes with names given by
# the actual DM names. Some udev environment variables are set
# for use in later rules:
#   DM_NAME - actual DM device's name
#   DM_UUID - UUID set for DM device (blank if not specified)
#   DM_SUSPENDED - suspended state of DM device (0 or 1)
#   DM_UDEV_RULES_VSN - DM udev rules version

KERNEL=="device-mapper", NAME="(DM_DIR)/control"

SUBSYSTEM!="block", GOTO="dm_end"
KERNEL!="dm-[0-9]*", GOTO="dm_end"

# Set proper sbin path, /sbin has higher priority than /usr/sbin.
ENV{DM_SBIN_PATH}="/sbin"
TEST!="$env{DM_SBIN_PATH}/dmsetup", ENV{DM_SBIN_PATH}="/usr/sbin"
TEST!="$env{DM_SBIN_PATH}/dmsetup", GOTO="dm_end"

ACTION!="add|change", GOTO="dm_end"

# Normally, we operate on "change" events only. But when
# coldplugging, there's an "add" event present. We have to
# recognize this and do our actions in this particular
# situation, too. Also, we don't want the nodes to be
# created prematurely on "add" events while not coldplugging.
ACTION=="add", ENV{STARTUP}!="1", NAME="", GOTO="dm_end"

# "dm" sysfs subdirectory is available in newer versions of DM
# only (kernels >= 2.6.29). We have to check for its existence
# and use dmsetup tool instead to get the DM name, uuid and 
# suspended state if the "dm" subdirectory is not present.
# The "suspended" item was added even later (kernels >= 2.6.31),
# so we also have to call dmsetup if the kernel version used
# is in between these releases.
TEST=="dm", ENV{DM_NAME}="$attr{dm/name}", ENV{DM_UUID}="$attr{dm/uuid}", ENV{DM_SUSPENDED}="$attr{dm/suspended}"
TEST!="dm", IMPORT{program}="$env{DM_SBIN_PATH}/dmsetup info -j %M -m %m -c --nameprefixes --noheadings --rows -o name,uuid,suspended"
ENV{DM_SUSPENDED}!="?*", IMPORT{program}="$env{DM_SBIN_PATH}/dmsetup info -j %M -m %m -c --nameprefixes --noheadings --rows -o suspended"

# dmsetup tool provides suspended state information in textual
# form with values "Suspended"/"Active". We translate it to
# 0/1 respectively to be consistent with sysfs values.
ENV{DM_SUSPENDED}=="Active", ENV{DM_SUSPENDED}="0"
ENV{DM_SUSPENDED}=="Suspended", ENV{DM_SUSPENDED}="1"

# This variable provides a reliable way to check that device-mapper
# rules were installed. It means that all needed variables are set
# by these rules directly so there's no need to acquire them again
# later. Other rules can alternate the functionality based on this
# fact (e.g. fallback to rules that behave correctly even without
# these rules installed). It also provides versioning for any
# possible future changes.
ENV{DM_UDEV_RULES_VSN}="1"

ENV{DM_NAME}=="?*", NAME="$kernel", SYMLINK+="(DM_DIR)/$env{DM_NAME}"

# We have to ignore further rule application for temporary
# cryptsetup devices. But don't forget to send the notification!
ENV{DM_UUID}=="CRYPT-TEMP-?*", GOTO="dm_last_rule"
ENV{DM_UUID}!="?*", ENV{DM_NAME}=="temporary-cryptsetup-?*", GOTO="dm_last_rule"

GOTO="dm_end"

LABEL="dm_last_rule"
ENV{DM_COOKIE}=="?*", RUN+="$env{DM_SBIN_PATH}/dmsetup udevcomplete $env{DM_COOKIE}"
OPTIONS+="last_rule"

LABEL="dm_end"