Article:		Automated Backups with Existing Tools
Subject:		incremental backup without archive bit?
Date:		2005-08-07 07:07:38
From:		gebseng
how is it possibel to make correct incremtal backups under the os x file system, which has no archive bit? the obvious problem is, that the backup software can determine whether or not to add a file only by it's creation or modification date. BUT a file that has been added to the source folder since the last backup that has NOT been modified AND has an older creation date (e.g: an older photo imported from a digital camera) will be left out of a new backup and will not be backuped at all.

Showing messages 1 through 2 of 2.

• incremental backup without archive bit?
  2005-12-07 09:43:12  mp459 [Reply | View]
  
  
  I, too, use rsync. I do not have an external HD, but I _do_ have an exteranl dvd burner, and internal CD burner. I do a full backup to my DVD and then incrementals (differentials, actually) using rsync to a disk image which I then burn to CD. Using the --compare-dest=the_DVD arg in rsync, I can keep a full backup on a DVD and differentials on CDs.
  

• incremental backup without archive bit?
  2005-08-07 13:38:52  peterhickman [Reply | View]
  
  
  Well for each backup archive you could create a catalog of the files that are in the archive along with their size, creation and modification dates and a sha1 checksum. Then when creating an incremental archive you only have to compare the files you are processing to the catalog to decide which files to include.
  
  You do not necessarily need to keep the old archives available but you would need to keep the last full catalog to hand.
  
  Infact there is a tool in OS X called mtree that does just that. It builds a catalog of the filesystem and can be used to compare the catalog against the current filesystem and report any differences such as files added or removed, file sizes or checksums changing. From this report you could then decide which files to add to your incremental archive.