Can't OSX boot from external usb?

majorp

macrumors 6502
Original poster
Nov 28, 2005
314
0
UK !!!
I have made a clone of my HD onto my external which has been formatted with GUID but icannot seem to make it boot. whenever i try it just shows the folder with the ? mark in it. i have searched and found nothing helpful. does anybody have any ideas? thanks
 

FredClausen

macrumors regular
Aug 7, 2006
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KALM
Probably a corrupt file, but out of curiosity what kind of drive are you trying to boot from? Firewire or USB?

Edit: I feel stupid. I could have read what kind of drive you had in your title. As gauchogolfer said below, you can't use USB to boot from.
 

gauchogolfer

macrumors 603
Jan 28, 2005
5,555
5
American Riviera
PPC Macs can boot from external firewire drives, but not usb ones.

This was one of the reasons people were upset they dropped fw support from new ipods.

Cheers

Edit: updated to reflect the discovery that Intel macs can boot from usb drives.
 

Mitthrawnuruodo

Moderator emeritus
Mar 10, 2004
13,798
167
Bergen, Norway
I've made a bootable backup of my internal using SuperDuper! onto my external USB2 drive. That shows up in the StartupDisk.prefPane on my MacBook (though I haven't actually tried booting from it).

I also used to be able to boot from a USB1 drive with my Pismo... :cool:
 

FredClausen

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Aug 7, 2006
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KALM
mad jew said:
I was under the impression that Intel Macs can boot from USB, but I might be wrong. I am wrong so very often these days. :(
No, you can't. I think it has to do with how USB isn't as stable bandwidth wise as FireWire. I'm sure the real explanation is much more technical :rolleyes:
 

plinden

macrumors 68040
Apr 8, 2004
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3
I've heard lots of reports that you can boot from USB drives on Intel Macs. I've only done it on Firewire drives, but I have a small USB external drive at home that I'm not using any more. I'll try it out tonight and give a definitive report later.

Edit: Actually, my external firewire drive here, which has OS X installed on it as a backup, is dual firewire/usb. Give me a few minutes and I'll swap over the cables and reboot.

Edit2: Boots no problem using USB. It's noticeably slower to boot, I didn't time it though, but it's usable. I'll try the other drive later or at the weekend, whenever I can get time, and try it. One thing to note is, it's not a clone of my drive, it's a separate install of OS X.
 

FredClausen

macrumors regular
Aug 7, 2006
170
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KALM
Mernak said:
PPC macs cant boot from USB2 but Intel macs work just fine. I have a 250GB external HD that I occasionally boot from.
Oh?

*runs off to try booting on my external disk on Macbook*
 

majorp

macrumors 6502
Original poster
Nov 28, 2005
314
0
UK !!!
sorry, its a macbook pro. just don't know why it won't boot. probably currupt. thanks anyway.
 

mad jew

Moderator emeritus
Apr 3, 2004
32,199
6
Adelaide, Australia
Yeah, most likely corrupt. Maybe try installing OSX freshly onto the external and then booting from it. That way you can work out whether it's a problem with the data or with the enclosure/drive/cable that's preventing you from booting at the moment. :)