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Background: I want to keep my virtual machine synced across different computers using Dropbox. It currently uses an 8 GB, dynamically allocated virtual disk image.

I haven't tested this extensively, but in theory, the slightest modification I make to my disk image would cause the corresponding 2 GB file to be re-uploaded to Dropbox in its entirety. If that is so, then splitting the disk image into chunks of, say, 64 MB, would save me a lot of bandwidth.

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I wonder if in this situation, having seperate drive images for seperate partitions would be a good idea. At the very least keeping /home seperate would reduce changes to the other drive significantly – Journeyman Geek Oct 20 '12 at 2:29
That's a very good idea! I had toyed with the idea of somehow linking /home to a VirtualBox share synced through Dropbox, but I discarded it because Dropbox usually messes up the permissions. Yours is better. – jSepia Oct 20 '12 at 2:35
Even better idea posted as an answer. Differencing disk images. – Journeyman Geek Oct 20 '12 at 2:40
C:\Program Files\Sun\xVM VirtualBox>VBoxManage createhd 
VirtualBox Command Line Management Interface Version 3.0.0
(C) 2005-2009 Sun Microsystems, Inc.
All rights reserved.


VBoxManage createhd         --filename <filename>
                            --size <megabytes>
                            [--format VDI|VMDK|VHD] (default: VDI)
                            [--variant Standard,Fixed,Split2G,Stream,ESX]
                            [--type normal|writethrough] (default: normal)
                            [--comment <comment>]

The command for creating images in virtualbox dosen't support that, tho its vmware varient seems to. Creating a vmware vmdk would be one option, but who wants to install another installer? There's better approaches

There's a few approaches you might want to try. For one, split up commonly used partitions from less commonly used ones, for example /home will be altered more often, as might /var. so having them as seperate disk images would help a littlr.

Switch to differencing disk images - this would create files with just the changes. Even more efficient bandwidthwise, and you'd only move the changes.

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I'm not sure if using differencing disk images would work as well, because my virtual machine is intended as a software testbed and I feel that making regular snapshots would only slow me down. But you did give me the answer - creating the disk using VMWare would solve my problem, along with having a separate /home disk image. – jSepia Oct 20 '12 at 2:53
@jSepia the differencing image would grow over time when you make changes, until it reaches a size which seems not acceptable to you. Then you can make a new snapshot (and optionally destroy the old one, if you do that, a full upload of the disk image to Dropbox will be triggered once). Then the process repeats. – vadipp May 16 '13 at 7:38

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