README

Ever wanted to convert a raw partition to .dmg, fast? This repo is what you need!

See also the original README for libdmg-hfsplus.

Why?

Sometimes you have really big files to convert to .dmg, and want it to go fast. Other builds of libdmg-hfsplus will be quite slow and use just one core.

An example use case is backing up Mac partitions on a multi-boot system. You can make a quick backup with dd or clonezilla, and it's easy to restore. But should you ever need to restore to a partition of a different size, you'll need to convert to .dmg and use Disk Utility.

With other tools, that conversion can be slow. On a 12-core system, my 200 GB partition (pre-compression) took over two hours to convert. But this build of libdmg took just 10 minutes!

Installation

• Install cmake, and headers for zlib and lzfse.
  • Eg: brew install cmake lzfse
  • Eg: apt install cmake zlib-dev liblzfse-dev
• Configure with cmake: cmake . -DCMAKE_BUILD_TYPE=Release
• Build: make -j6
• Copy dmg/dmg somewhere in your path

Usage

• Convert an image to dmg: dmg dmg input.img output.dmg
• Or use - as a file argument to use standard input/output

Example, with a disk image compressed with pixz:

cat giant.img.pxz | pixz -d | dmg dmg - output.dmg

How

• Changed dmg compression to use a parallel algorithm
• Made CRC32 calculation parallel, too
• Allowed streaming input in most cases