Mac 101: Yes, Intel Macs can be booted from an external USB drive

More Mac 101, our ongoing series of tips and tidbits for new Mac users.

Update: As the comments point out and Low-End Mac confirms, support for USB booting was present in the Mac OS 9 era with the introduction of dual-channel USB in 1999, available first on the slot-loading iMac and one model of the AGP PowerMac G4; however, your mileage and performance may vary when trying to get these machines to boot Mac OS X from USB devices (as has been previously reported on TUAW). Our apologies for the error!

When I wrote my post Tuesday about booting a Mac off an external USB hard drive, I was surprised how many people followed up to tell me that it wouldn't work, and that I needed a Firewire drive to externally boot a Mac.

While [much] older machines did indeed need Firewire for bootable external media, that is no longer true. Since the release of the Intel Mac computers [and well beforehand -- see update above], and with Mac OS X 10.4.5 or later, you can start up from an installed system on a USB hard disk. Here's the Apple support document that tells you how to do it.

I didn't think it was possible either, and when I bought my MacBook Pro last year, I was wishing I could boot from a USB drive because of the easy availability of inexpensive storage. A little online research revealed the obscure truth. USB booting generally works fine from a bus-powered portable drive as well as a powered USB desktop drive. In my case, I booted up just fine from a portable with no external power supply. Check the support document linked above for more details.

So have at it -- either install a clean version of Leopard or Tiger on the drive, or use your favorite bootable-backup utility to clone your existing install to the USB volume. It's a good thing to know as Apple seems to be determined to bury Firewire on the lower priced laptops it sells.

It is also possible to boot an Intel Mac from a USB flash drive. That is a bit more involved, and there are several methods. One is Das Boot, a free utility from Sub Rosa that allows you to convert original disks from DiskWarrior, Drive Genius, TechTool Pro and others to a flash drive. Let Google be your friend on this. Many people have put their favorite rescue utility on a bootable flash drive to save them from any problems in the field.

Before you ask; no, USB does not support target disk mode -- a sore point for MacBook Air and unibody MacBook owners.

Thanks to Dave and others who wrote in asking about this, and thanks to many readers who wondered about the ability of older PPC Macs to do this as well.

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Source: http://support.apple.com/kb/HT1948

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More Mac 101, our ongoing series of tips and tidbits for new Mac users. Update: As the comments point out and Low-End Mac confirms,...

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CJH

Since people have cited Windows XP limitations as the reason for not being able to run from an external drive, would you be able to do that with Ubuntu or your Linux distro of choice?

December 25 2008 at 11:07 PM Report abuse Permalink rate up rate down Reply

alefrag

Sorry about my ignorance, but could I use my original Mac OS X installation disk that came with my MacBook, to create this USB Boot?

December 20 2008 at 10:14 AM Report abuse Permalink rate up rate down Reply

Rob Bazinet

I have used an external usb hd to backup my MacBook Pro using SuperDuper. After upgrading my internal HD I booted easily off of the USB and restored the backup.

It all worked like a champ.

December 19 2008 at 1:14 PM Report abuse Permalink rate up rate down Reply

Ron

Now try it with linux, since we all new that you can boot Leopard from you USB, hell even your iPod.

December 19 2008 at 11:13 AM Report abuse Permalink rate up rate down Reply

Dman

hi, im new to macs had my imac now for a few months and love it.. my question is could i install xp on a external hard drive? i know about boot camp and vmware but having it completely separate on a external sounds good. thanks in advance.......

December 19 2008 at 5:20 AM Report abuse Permalink rate up rate down Reply

1 reply to Dman's comment

Dman- No, unfortunately Windows does not like to run from an external drive on a Mac.

The best way to get a decent-sized Windows XP partition on your Mac is to upgrade the internal hard drive by whatever amount of space you wish to dedicate to Windows. Drop a big drive in there, and just make a big NTFS partition for Boot Camp.

The good news is that Windows XP works quite well on the iMac. I loved mine, and would have kept it if I didn't need to focus on portability. With SP3 (Service Pack 3) from Microsoft, Windows XP runs FAR better than Vista and is finally a finished product! ;)

December 19 2008 at 11:48 AM Report abuse Permalink rate up rate down Reply

Jeff

owell, I've done it and done it multiple times, earlier last year, this is no news to me.

December 19 2008 at 12:58 AM Report abuse Permalink rate up rate down Reply

Jason

I've had no problems booting my MBP off a cloned drive on USB, but it runs considerably slower than booting off a cloned drive on Firewire 400. Point is, it works, and it's cheap, but I'm likely to only buy Firewire external drives because of this. I tried just this once to buy a cheap WD MyBook USB, and I now regret not paying extra for Firewire.

December 18 2008 at 6:23 PM Report abuse Permalink rate up rate down Reply

mr kitty

You can boot Intel Macs from USB flash drives without using third party utilities. Tho, not ALL flash drives work. I had a Lexar Firefly (4GB) that booted Tiger (and all my tools), and two Sandisk Cruzer Contours (8GB, 16GB) that boot Leopard (and my tools).

The secret was GUID partitioning. I Carbon Copy Cloned a system set up on another drive to do it, but I have since installed Leopard straight onto the 16GB Cruzer.

I also have a Kensington Data Traveler 16GB that WON'T boot, no matter what I try. So YMMV.

December 18 2008 at 5:55 PM Report abuse Permalink rate up rate down Reply

max

Anyone successful at creating a bootable USB flash drive with Disk Warrior on it. TechTool is easy using ProToGo to create a bootable USB flash drive for both non-Intel and Intel. I need to build a bootable USB flash drive for Disk Warrior for non-Intel and Intel.

Das Boots doesn't work well on Leopard. On Tiger it works and I could create a Disk Warrior partition but I it would not boot Intel. On non-Intel it would boot but I could not run Disk Warrior.

Anyone have advise or tutorials on how to archive this?

Thanks.

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www.mailbysnail.com

December 18 2008 at 4:35 PM Report abuse Permalink rate up rate down Reply

Alex

"Before you ask; no, USB drives do not support target disk mode -- a sore point for MacBook Air and unibody MacBook owners."

Okay, I'm a tad confused as to what this means... Well, I mean I get you're saying it isn't supported, but isn't Target Disk Mode a computer-to-computer connection? What would a usb drive have to do with it?

December 18 2008 at 4:07 PM Report abuse Permalink rate up rate down Reply