rc: backup DUID for /var MFS et al

Make sure to delete the backup prior to backing up to mimick
the current system state.  Same goes for restore, no backup
means remove the DUID to sync the system state to what it was.

plist

@@ -74,6 +74,7 @@
 /usr/local/etc/rc
 /usr/local/etc/rc.backup_captiveportal
 /usr/local/etc/rc.backup_dhcpleases
+/usr/local/etc/rc.backup_duid
 /usr/local/etc/rc.backup_netflow
 /usr/local/etc/rc.backup_rrd
 /usr/local/etc/rc.bootup

src/etc/rc.backup_duid

@@ -0,0 +1,16 @@
+#!/bin/sh
+
+BACKUPFILE="/conf/dhcp6c_duid"
+BACKUPTARGET="/var/db/dhcp6c_duid"
+
+if [ "${1}" = "restore" ]; then
+	rm -f "${BACKUPTARGET}"
+	if [ -f "${BACKUPFILE}" ]; then
+		cp "${BACKUPFILE}" "${BACKUPTARGET}"
+	fi
+else
+	rm -f "${BACKUPFILE}"
+	if [ -f "${BACKUPTARGET}" ]; then
+		cp "${BACKUPTARGET}" "${BACKUPFILE}"
+	fi
+fi

src/etc/rc.syshook.d/20-backup.early

@@ -1,6 +1,6 @@
 #!/bin/sh
 
 # Restore backups from previous shutdown
-for BACKUP in captiveportal dhcpleases netflow rrd; do
+for BACKUP in captiveportal dhcpleases duid netflow rrd; do
 	/usr/local/etc/rc.backup_${BACKUP} restore
 done

src/etc/rc.syshook.d/90-backup.stop

@@ -1,6 +1,6 @@
 #!/bin/sh
 
 # Backup volatile internals
-for BACKUP in captiveportal dhcpleases netflow rrd; do
-	/usr/local/etc/rc.backup_${BACKUP} stop
+for BACKUP in captiveportal dhcpleases duid netflow rrd; do
+	/usr/local/etc/rc.backup_${BACKUP}
 done