Mac Geeks

In a previous article I described how to setup an encrypted TimeMachine Backup. That used to work fine until a few month ago. I noticed back then that the automatic scheduled backup can’t seem to mount the encrypted volume anymore. However when I click on the TimeMachine icon in the menu bar and select “Backup Now” it will work just fine.

I couldn’t figure out what was the root cause of this behavior. But at least I found a workaround now. There is a free tool to change the schedule of the TimeMachine backups called TimeMachineEditor. This uses an alternate scheduling mechanism to trigger regular backups. I set the schedule to be 1h and it works just fine now.

Imagine you have to switch the mainboard of your Apple computer. More specific: the network card or even more specific the MAC address of your network card. Then your exisiting TimeMachine backup will no longer be recognized as valid. This is because of the fact that the Backup folder on the TimeMachine Volume is tagged with the MAC address of your computer. That should prevent you from accidently using TimeMachine backups from different computers. But will also bring you trouble if your MAC address changes for some reason (as in case of mainboard switch during maintenance).

Unfortunately there is no obvious way to tell TimeMachine to use an pre exisiting Backup. TimeMachine would simply start a new backup if you try to continously use the old Volume. The old Backup folder may be even moved to the Trash on that Volume. Obviously this is not what you want.

But when you try to move the original Backup out of Trash, you’ll notice that even the super user “root” doesn’t have the privileges to do that.

But don’t worry. You’re not all lost. What is causing you the trouble is the fact that the MAC address is somewhere tagged on the Backup folder and that Apple additionally uses ACLs (Access Control Lists) on the backup volume. These are basically some additional security settings which should prevent unauthorized or unwanted changes.

So the easiest way to get the Backup working again is to disable the ACLs on the volume, change the MAC address tag of the Backup folder and the re-enable the ACLs on the volume.

This can be done in the Terminal.app as superuser:

cd /Volumes/TimeMachineBackup
fsaclctl -p /Volumes/TimeMachineBackup -d
xattr -w com.apple.backupd.BackupMachineAddress 00:16:cb:90:62:0d `hostname`
fsaclctl -p /Volumes/TimeMachineBackup -e  

After that your original Backup should be recognized by TimeMachine.

This tutorial was found here: CyberHQ NL

If you don’t have MacOS X 10.5 (Leopard) but as well starving for a nice and easy backup then try this shell script. MacOS X provides some simple command line tools for doing a convinient backup out of the box. I wrote a little shell script which sports RSYNC to do regular backups and even archive deleted files for a certain time.

Simply modify your source and destination folder in this script and call it regularly. This can be done with cron. Your contrab entry should look something like this:


0 */2 * * * /Users/youraccount/pmt.sh > /dev/null 2>&1


This will start the script every full 2 hours. Should be sufficient.

#!/bin/bash
# poor man's timemachine backup script
# Author:
# $Date: 2009-01-07 13:46:08 +0100 (Wed, 07 Jan 2009) $
# $Author: fzurell $
# $Revision: 93 $
# $HeadURL: http://fzurell@svn.explain-it.org/trunk/tools/pmt.sh $

# this is where your backup will go
# hence the special character " " ... must be quoted with \
BACKUPDIR=/Volumes/Time\ Machine/pmt

# This is the folder where the Backup should start from
# it will be backed up recursivly
SOURCE=/Users/fzurell/Music

####################################################################
LANG=de_DE.UTF-8
WDAY=`date +%A`
MDAY=`date +%d`



# if you call this script without any parameter
# then deleted files will be archived for one week
# you can optionally choose to keep them one month

case $1 in
	"woche")
		BDAY=$WDAY
		;;
	"monat")
		BDAY=$MDAY
		;;
	"--help")
		echo "Usage: $0 [woche | monat]"
		exit 10
		;;
	*)
		BDAY=$WDAY
		;;
esac


if [ ! -d "$BACKUPDIR" ]; then
		exit 1
fi

/usr/bin/rsync -a -q --delete -b --backup-dir="$BACKUPDIR/$BDAY" "$SOURCE" "$BACKUPDIR/BACKUP"

if [ $? -eq 0 ]; then
	say "Your Backup finished successfully."
else
	say "Sorry, there went something wrong with your Backup."
fi