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Restore a full-disk .dmg file to a raw block device
Authored by: newbie44 on Sep 06, '13 07:19:23PM

Many thanks to you and daveosborne for your hints !

1) I'm currently dumping the content of a .dmg file to an external disk.


2) "with an appropriate buffer size to copy over the whole block image, including partition table and boot sector"
-> what do you mean by that and how can I determine which buffer size is appropriate ?
-> how did you determine the 131072 size ?

For my use I trusted blindly the example and used the bs=131072 option. Untill now it seems to be working... (it's still copying).

I'm currenlty getting tons of lines on my terminal screen that look like :

...
CZlibDecompressor::decompressData: src 0x02E4AA97 srcLen 116073
CZlibDecompressor::decompressData: dest 0x02E26000 destLen 262144
CZlibDecompressor::decompressData: src 0x02E61F0D srcLen 20723
CZlibDecompressor::decompressData: dest 0x02E26000 destLen 262144
...

with sometimes long series of
...
CZlibDecompressor::decompressData: src 0x02E66B71 srcLen 1167
CZlibDecompressor::decompressData: dest 0x02E26000 destLen 262144
CZlibDecompressor::decompressData: src 0x02E66B71 srcLen 1167
CZlibDecompressor::decompressData: dest 0x02E26000 destLen 262144
...

I notice the destLen (I suppose it means block destination length) 262144 is exactly the double of the bs=131072 that was used before. I'm curious if anyone can help me understand this. Does this mean the source data is sparsed over the destination disk by blocks of 131072 or 262144 bytes, thereby fragmenting the disk ?

In your replies, please kindly take into account that I'm a French newbie with a fair level of ignorance of OSX command line technical slang, however not completely ignorant with computers either (one piece of paper even says I'm an engineer :), it's just that I don't understand what the buffer size technically means here.

Many thanks in advance for your insights !



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