Mkextunpack is a utility used in Mac OS X and Darwin. This utility is used to expand (unpack) .mkext file into its component .kext files. A .kext is a kernel extension, basically a driver, whereas a .mkext is a multiple kernel extension, basically a group of .kexts compressed in one file. This utility is located in the directory /usr/sbin. Another utility, kextcache, is the opposite of Mkextunpack, in that it allows .kext files to be compressed into a single .mkext file.
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Mkextunpack Wikipedia(Text) CC BY-SA