saving uncommitted changes in /etc prior to emerge run

init.d/device-mapper

@@ -0,0 +1,111 @@
+#!/sbin/runscript
+# Copyright 1999-2013 Gentoo Foundation
+# Distributed under the terms of the GNU General Public License v2
+# $Header: /var/cvsroot/gentoo-x86/sys-fs/lvm2/files/device-mapper.rc-2.02.95-r2,v 1.2 2013/04/09 11:00:26 ssuominen Exp $
+
+depend() {
+	# As of .67-r1, we call ALL lvm start/stop scripts with --sysinit, that
+	# means dmeventd is NOT notified, as it cannot be safely running
+	before dmeventd checkfs fsck
+	after modules
+}
+
+dm_in_proc() {
+	local retval=0
+	for x in devices misc ; do
+		grep -qs 'device-mapper' /proc/${x}
+		retval=$((${retval} + $?))
+	done
+	return ${retval}
+}
+
+# char **get_new_dm_volumes(void)
+#
+#   Return dmsetup commands to setup volumes
+get_new_dm_volumes() {
+	local volume params
+
+	# Filter comments and blank lines
+	grep -v -e '^[[:space:]]*\(#\|$\)' /etc/dmtab | \
+	while read volume params ; do
+		# If it exists, skip it
+		dmvolume_exists "${volume%:}" && continue
+		# Assemble the command to run to create volume
+		echo "echo ${params} | /sbin/dmsetup create ${volume%:}"
+	done
+
+	return 0
+}
+
+# int dmvolume_exists(volume)
+#
+#   Return true if volume exists in DM table
+dmvolume_exists() {
+	local x line volume=$1
+
+	[ -z "${volume}" ] && return 1
+
+	/sbin/dmsetup ls 2>/dev/null | \
+	while read line ; do
+		for x in ${line} ; do
+			# the following conditonal return only breaks out
+			# of the while loop, as it is running in a pipe.
+			[ "${x}" = "${volume}" ] && return 1
+			# We only want to check the volume name
+			break
+		done
+	done
+
+	# if 1 was returned from the above loop, then indicate that
+	# volume exists
+	[ $? = 1 ] && return 0
+
+	# otherwise the loop exited normally and the volume does not
+	# exist
+	return 1
+}
+
+# int is_empty_dm_volume(volume)
+#
+#   Return true if the volume exists in DM table, but is empty/non-valid
+is_empty_dm_volume() {
+	local table volume=$1
+
+	set -- $(/sbin/dmsetup table 2>/dev/null | grep -e "^${volume}:")
+	[ "${volume}" = "$1" -a -z "$2" ]
+}
+
+
+start() {
+	if [ -e /proc/modules ] && ! dm_in_proc ; then
+		modprobe dm-mod 2>/dev/null
+	fi
+	# Ensure the dirs exist for locking and running
+	checkpath -q -d -m 0700 -o root:root /run/lvm /run/lock/lvm
+
+	local x volume
+	
+	if [ -x /sbin/dmsetup -a -c /dev/mapper/control -a -f /etc/dmtab ] ; then
+		[ -n "$(get_new_dm_volumes)" ] && \
+			einfo " Setting up device-mapper volumes:"
+	
+		get_new_dm_volumes | \
+		while read x ; do
+			[ -n "${x}" ] || continue
+	
+			volume="${x##* }"
+	
+			ebegin "  Creating volume: ${volume}"
+			if ! eval "${x}" >/dev/null 2>/dev/null ; then
+				eend 1 "  Error creating volume: ${volume}"
+				# dmsetup still adds an empty volume in some cases,
+				#  so lets remove it
+				is_empty_dm_volume "${volume}" && \
+					/sbin/dmsetup remove "${volume}" 2>/dev/null
+			else
+				eend 0
+			fi
+		done
+	fi
+}
+