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Recently I was experimenting with FreeBSD 7.4 i386 Install DVD on a Mac mini Intel 2006 on whose harddisk Mac OS X 10.5.8 was installed. My aim was to just see contents of the harddisk from the FreeBSD's Live CD section to remember several concepts about Unix and OSes in general.

But after I finished and ejected the FreeBSD DVD, I found that Mac mini no longer booted Mac OS X. After some inspection, I found that the first entry on the harddisk seems to have changed from "pmbr" to "mbr" and I think that might be causing the Mac mini not to boot Mac OS X. Here is the output of gpt command on this problematic harddisk: (#gpt -r show disk0)

start      size  index  contents
     0         1         MBR
     1         1         Pri GPT header
     2        32         Pri GPT table
    34         6
    40    409600      1  GPT part - C12A7328-F81F-11D2-BA4B-00A0C93EC93B
409640 233769824      2  GPT part - 48465300-0000-11AA-AA11-00306543ECAC

234179464 262151 234441615 32 Sec GPT table 234441647 1 Sec GPT header

You see, apart from the "mbr" not being "pmbr" every other entries are identical to the one which boots Mac OS X.

The question is: Can I repair this harddisk so that it becomes bootable by Mac mini again? Please note that I ask this mainly for learning and experimental purposes; I'd like to learn the internals of OS booting and harddisk partitioning. There's no crucial data on this harddisk. I have posted this same problem on 2 other sites but they either got no response or have been replied by people with insufficient knowledge on the topic. That's why I post this problem for the 3rd time.

Just one more note that may help you more precisely identify the problem: This problematic harddisk shows up in /dev (in Mac OS X's Terminal) only as /disk0 and not as /disk0s1 , /disk0s2.

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