On Fri, Jun 19, 2009 at 3:06 PM, Zachary Kotlarek <span dir="ltr"><<a href="mailto:zach@kotlarek.com">zach@kotlarek.com</a>></span> wrote:<br><div class="gmail_quote"><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
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On Jun 19, 2009, at 1:50 PM, David W. Body wrote:<br>
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Maybe "sparse, compressed, read-write" isn't the correct description because I only want to write it once, but hdiutil will create a sparse, compressed disk image from a directory as follows:<br>
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hdiutil create -srcfolder my_directory -format UDZO my-diskimage.dmg<br>
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That's just a gzip-compressed read-only disk image. UDZO is "sparse" in that the unallocated blocks aren't included in the image, but it can't grow as you add data because you can't add data.<br>
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hdiutil can create what it calls "sparse" images -- files (or bundles) that grow as you allocate blocks -- with the UDSP and UDSB formats. But in those formats the allocated blocks aren't compressed, the images simply excludes the unallocated blocks so that you don't need to consume the entire image size until it's actually used.<br>
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Are you trying to create a read-only image with compressed data or create a read-write image that excludes unallocated blocks? Or is there some third option I'm missing?<br>
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Zach</blockquote><div><br>Zach,<br><br>Thanks for the clarification. I realize now that I didn't really ask the question I intended to.<br><br>I want to be able to create backups of directories in a reasonably efficient compressed format. I don't need to be able to add data after the backup is created. Under OS X, I've found that hdiutil does a decent job of this with the added bonus that the disk images it creates are convenient to work with because they can easily be mounted and unmounted, transferred to other media, etc. I'm looking for something similar on Linux. My fallback will be gzipped tar files, but that feels like a step backward.<br>
</div></div><br>--David<br><br>