How to merge shapefiles?

Rsync to Merge Disk Images?

• Should I use rsync (instead of rsnapshot) to pare down Mac disk image backups? I've used SuperDuper to make several disk image backups of a boot drive. Let's say they're called backup-090107.dmg, backup-090114.dmg, backup-090121.dmg, and so on. I want to merge all these into a single backup directory, RETAINING incremental backups. So if file-a.txt changed on Jan 16 2009 (between backup-090114 and backup-0090121), I'd end up with a copy of how it was on 090114 and also a copy of how it was on 090121. I tried rdiff-backup but gave up on it due to insane slowness. (It takes SuperDuper 5-6 hours to back up 60-70 GB over USB2; rdiff-backup was taking about 16 hours to back up just the 7GB applications directory. Yikes.) I've started looking at rsnapshot, but I don't think that's what I want for this initial merge ... although it might be what I want for any subsequent backups, once I've got the disk images merged. So: * am I correct in thinking that rsync is best for merging these dmgs? * would the following commands do what I want to do - so I end up with a single copy of any file that hasn't changed, plus incremental backups of each file that HAS changed? rsync -a --delete --numeric-ids --relative --delete-excluded --xattrs --exclude=/this/ --exclude=/that/ \ /Volumes/backup-090107 /Volumes/BackupDrive/big-old-merge-directory/backup-090107/ rsync -a --delete --numeric-ids --relative --delete-excluded --xattrs --exclude=/this/ --exclude=/that/ \ /Volumes/backup-090114 /Volumes/BackupDrive/big-old-merge-directory/backup-090114/ * should I switch to rsnapshot after merging, or continue using rsync? If I continue with rsync, would I use something like rsync -a --delete --numeric-ids --relative --delete-excluded --xattrs --exclude=/this/ --exclude=/that/ \ /MyHardDrive /Volumes/BackupDrive/big-old-merge-directory/backup-todaysdate/ Extra bonus points for lists of directories you like to exclude, or pointers to pages that list appropriate OS X (10.4) directories to exclude. (I DO want to back up even big directories; I don't need to back up the unnecessary or dangerous - for example, I know most folks exclude .Spotlight-V100.) Once I've merged the backups (and verified them, of course), I'll be deleting the disk images to free up space for future backups. (And I'm doing full, bootable backups to a different drive; this is just my attempt to get good incremental backups.) Many, many thanks!

• Answer:

  The canonical article for this (and the one that rsnapshot references) is http://www.mikerubel.org/computers/rsync_snapshots/. I think you're going to want to create one directory per .dmg file -- the first copy is a straight rsync, and each subsequent one will use --link-dest to link to the previous. You'll end up with a set of dated directories, each with a complete image, and every file will be hard linked so that only one copy of the file will exist, maximum.