Image Format

Version 5 (Nikos Skalkotos, 11/23/2011 04:13 pm)

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h1. Image Format
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Right now we support 4 different types of images:
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* extdump
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* ntfsdump
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* diskdump
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* custom
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h2. extdump & ntfsdump
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Those two formats are raw copies (using dd) of partitions hosting Linux systems on ext{2,3,4} and Windows systems on ntfs filesystems respectively.
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Partitions hosting a Windows or Linux system that are suitable for dumping should have the following properties:
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* Be the first partition in the filesystem
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* The OS they host should not depend on any other partitions
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* Start at sector 2048
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* Have a bootloader installed in the partition
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* Have the root device in /etc/fstab specified in a persistent way, using UUID or LABEL (for extdump only)
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h3. Known Issues
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* For linux systems, having grub installed in the partition is fragile and things can go wrong when resizing the partitions, especially when shrinking.
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* Swap space is not supported.
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* More complicated partition schemes are not supported.
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h2. diskdump
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Diskdump is a newer format that overcomes most of the aforementioned issues. This format is a raw copy (dd) of a whole disk, instead of a partition.
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This design has the following benefits:
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* Swap partitions are supported
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* The system may use multiple partitions:
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** dedicated partitions for /boot, /home etc in linux
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** system and boot partition in Windows
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* There are no restrictions on partitions starting sectors
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Although diskdump is a lot more flexible that the older formats, there are still some rules to follow:
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* All devices in fstab should be specified by persistent names (UUID or LABEL)
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* LVMs and extended partitions should be avoided