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I want to create a whole disk image and some incremental of them. First I created a disk backup with

dd if=/dev/disk1 of=/Volumes/USBDrive/diskimage.img bs=1024k

and there is my problem: how can I create an incremental disk image of diskimage.img?

And how is the way back from the incremental image to a complete disk?

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dd isn't really designed for doing something like that. And trying to find a way to make dd do incrementals is probably a lot of effort that will end in disaster.

What you're asking about is called snapshots.

On Linux there are two main ways to get snapshots:

  1. Use LVM
  2. Use BtrFS

I would highly recommend using LVM because of its maturity over BtrFS. You should check your distribution's documentation on how it is recommended to set up LVM, or the LVM HOWTO on the Linux Documentation Project website.

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There are also zfs (both fuse and ZoL) and ddsnap. Using LVM, if you want multiple snapshots, you'll have to use the new thin provisioning support or the performance will get very poor after a few snapshots, and it's not much more mature than btrfs. I'm not sure why there's a /linux tag on this question as the /dev/disk1 and /Volume suggests MacOS/X instead. – Stéphane Chazelas Oct 30 '12 at 20:15
I didn't mention ZFS because it's non-trivial to use ZFS as a root filesystem for Linux. I actually had paragraphs in there referring to ZFS, but decided to take them out. – bahamat Oct 30 '12 at 23:38

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