Re: [rdiff-backup-users] backup misses files with older date

[Chris Wilson]

Hi,

On Wed, 7 Jan 2009, bt101 wrote:

> I installed rdiff-backup and used it for a few days.  I was eager to see 
> how it would handle a small change to a large (2G) truecrypt file.  I 
> added a small file into the truecrypt file and then performed a backup. 
> To my surprise, the truecrypt file was completely missed from the 
> backup.  I then looked at the modify date of the truecrypt file and it 
> was old.  It seems truecrypt will preserve the modify date (there's a 
> setting to change it if you wish).

This is an annoying and pointless misfeature of truecrypt. It causes 
problems for other backup software as well. Turn it off if you want to 
back up truecrypt volumes, and complain to the developers of truecrypt. 
Timestamps exist for a reason and subverting them by default is dangerous 
and pointless. I'm fairly sure that the ctime will change whenever the 
volume is accessed as the timestamp is reset, and therefore changing the 
mtime provides only the tiniest shred of obscurity.

> Be that as it may, am I to understand that backup programs will 
> completely miss files that NEED to be backed-up, simply because their 
> dates are old?  Do they not do a checksum or something?

Almost all backup software will honour timestamps. They exist for a 
reason. Software that changes the data without changing the timestamp is 
broken.

> Incidentally, I am also performing a dar backup of the filesystem as 
> well, and it also missed the backup of this modified file.
>
> Seems like a pretty big hole to me!

It is a big hole - in truecrypt.

Cheers, Chris.
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