Thursday, September 18, 2008

Follow up on why we make backups

After I got home I was able to retrieve a backup of the TrueCrypt volume from my Time Machine disk.  Unfortunately, the backup was from 9/11.  Time Machine does its differential backups based on the time a file was last modified.  Strangely, when decrypting a TrueCrypt volume (and this one is accessed at least five days per week), the "Date Modified" for the file is not changed.

So, to ensure that the volume is backed up every time I connect my Time Machine disk, I wrote an AppleScript to run the UNIX "touch" command, then placed that script in my login items.  Thus, everytime I login the volume's Date Modified attribute will be updated.  The AppleScript is one line:

do shell script "touch /Users/davemarkowitz/Documents/"

In my previous post I mentioned that I may implement an online backup system.  Instead of doing that, I think I'll setup a backup routine to copy the volume to a Linux box at my office, saving me a few bucks but still allowing me to have an easily accessed backup at work.

That may be an interim solution, though.  Yesterday I received two Apple XServes, each of which will be connected to an XServe RAID with over a terabyte of disk space.  One of the intended uses for them is to create workgroups storage space and backing up Rohan fits into that perfectly.


Cappy said...

This is CaptainSQL with a piece of free DBA advice. Make those backups! It's important!

This has been a CaptainSQL Public Service Announcement.

Doug said...

The timestamp not changing is a feature of TrueCrypt -- it allows you to plausibly state that the contents of that volume haven't changed recently.

There is an option in TrueCrypt which changes this behavior.

Honestly, I can't say that I've tried it but it was discussed on the "Security Now" podcast. The original question was in episode 134 with some follow up in episode 135. Transcripts are at and . Search for "Jungle Disk" on the page.

Also, I found your page while researching options for full disk encryption on a mac with support for Time Machine. You seem not to be doing that however.