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Connect machines via FireWire target disk mode System
This was news to me and has come in really handy in switching from my older iBook to a new TiBook. If you start up a PowerBook G4 (or a newer iBook) while holding down the "T" key, your computer will start up in "firewire target disk mode" ("t" standing for "target") It will then behave just like a firewire hard drive. Once you see the firewire logo on screen just connect that mac to any other computer with a standard firewire cable and its hard drive pops up on the other computers 'desktop.

I copied gigabytes of data (my entire Users folder) with ease this way. Also you could do this to run disk diagnostic software and such on the drive. Very handy.

[Editor's note: You should be aware that if you use target disk mode, the computer you connect the laptop to will have full access to everything on the laptop; permissions are not obeyed on the attached computer. Since you'll most likely be the one connecting the machines, this may not be a big concern to you ... but you should be aware of it. Thanks to an anonymous tipster for pointing this out to me.]
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Authored by: Jay on Apr 02, '02 12:24:29PM

It's very, very fast.

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handy for fixing machines
Authored by: eagle_eyes on Apr 02, '02 12:48:06PM

When you have a mac (with firewire of course) that will not boot it will most often still work in target disk mode making it possible to either fix the harddrive or at least back it up. The only down side is that at times the harddrive map is in such bad shape that you have to boot to OS 9 (on the working machine) to get it to recogize anything.

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handy for fixing machines
Authored by: serres on Apr 02, '02 06:36:15PM

as i bought defective ram and after three days i had some unresolvable errors on my filesystem i made a complete disk image with disk copy (make image from drive, use format DVD/CD master) before running any hard disk recovery tools. i think it might even be possible to mount the image and try the recovery on the image instead of the original drive.

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Security concerns
Authored by: randydarden on Apr 02, '02 01:06:54PM

Mention of Firewire Target Disk mode raises some serious security issues, especially for laptop users. If your machine was stolen, even if you had no OS 9 installed, someone could get to all your files by connecting it to another Mac via Firewire Target Disk mode.

Apple KBase doc #106482 discusses Open Firmware Password protection and how this can close this security hole (among others).

Still, someone could always remove the harddrive and place it in another laptop (or an external firewire case) and get to everything. Start looking at GPG.

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Security concerns
Authored by: rebug on Apr 02, '02 04:28:44PM

Physical access always equals root access. Firewire Target Disk Mode just makes it marginally easier.

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physical access
Authored by: Moo0 on Apr 03, '02 05:09:21AM

is indeed the word here. If the laptop is running X, it's quite easy to run it in single-user mode (root) and have access to just about anything.

The fact that one can copy 5 gb of data in 10 minutes makes it EASIER for sure; which just proofs the point to never leave your laptop out of sight - not even for 10 minutes...

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connect to windows machines
Authored by: serres on Apr 02, '02 06:29:47PM

there are several windows utils allowing access to mac hfs(+) file systems. there is an open source tool, but it doesn't support hard disks (too bad). but i found a commercial tool called macdrive (, which worked immediatly without any windows typical hazzles. it has a 2 weeks trial period, so for emergency or one-time actions this is a great way to get some GB of audio or DV data from a pc.

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Little behind the times...
Authored by: Anonymous on Apr 02, '02 07:55:23PM

This feature has been around since the PowerMac G3 B&W and the PowerBook Firewire. Isn't that about two years now?

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Yeah but.....
Authored by: eagle_eyes on Apr 02, '02 11:53:24PM

Isn't this the case most of the time. Apple throws in tons of extra features, many that they never tell many people about, and they are discovered in mass much latter. This is why when ever a PC person tells me that macs are behind I laugh and start showing all of these little tricks and features. They shut up really soon!

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Missing detail
Authored by: sjonke on Apr 03, '02 10:52:17AM

Something I forgot to mention was that when your done using your PowerBook or iBook this way, you press the power button to turn it off (shut down). Then start it back up like normal.

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damaged HD after use as a target disk
Authored by: ettorep on May 13, '02 03:30:10PM

I used my iBook (dual USB 2001) as a target disk with another iBook. <br>
I made a mistake when I was about to disconnect it and reboot: I did NOT unmount it, but just disconnected the
firewire cable. Even worse, I did a reboot on my ibook (probably because I was kinda stoned...) and got back
in T-mode, and then I tried to reconnect it via firewire. (I should have tried to reconnect it immediately, and .).
The mac using my iBook seemed to see it again, but when I tried to copy something from/to it, I had many
errors with code "-127" (which is a HFS error: "fsDSIntErr, Internal file system error" (from

Then, trying to reboot my ibook, I got a couple of kernel panic from OS-X, but it did complete the boot sequence
smoothly one time; instead, OS 9 completed the reboot without problems but then I got allot of errors
code -127 as well. <br>

Checking the partitions with Drive First Aid, there were errors saying "invalid sibling links".
Repair didn't work, both on 9 and X. <br>
I think one should be VERY careful with "target disk mode". A single error can cost you the file system integrity.
I know that I made a stupid thing: at least, I shouldn't have done that reboot after I improperly removed the
target disk.
Do you know if firewire HDs can have this kind of problem ? Since firewire is hot-swappable, I don't think that would be
very cool... neither is safe.... after all everyone does mistakes sometimes (especially when you're high). Maybe on firewire HDs
there's no problem because noone use the disk except for the computer: I mean, you HAVE TO use it with the
computer, so, even if it's "dirty", when you reconnect it to the computer it fix things up.

Do you know any solutions other than reinstalling everything?

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damaged HD after use as a target disk
Authored by: tombenson on May 13, '02 11:06:11PM

"-127" = HFS parent tree error.....

Diskwarrior shall be your savior here... but you may also want to try fsck'ing your way out of trouble... ;)

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damaged HD after use as a target disk
Authored by: ettorep on May 14, '02 08:30:15AM

well, when the damage occurred i didn't have diskwarrior so I couldn't do that.

Right now i already reformatted the whole thing down, since I had no important data on my disk (I clean-installed the systems a few days before.)

About fsck, I thought about that too late to do it. :)

Anyways, I was wondering about the target disk mode itself: is it safe ? did anyone experienced similar problems ? do you know anything more specific? I'd like to know different theories about the cause and possibly a technical explanation of how target disk mode works: i think it writes something on the HD (after all it screwed up mine) but i don't know anything else. I didn't find any in-depth explanation on the knowledge base (only a note on how to use it).
Thanks a lot!

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Connect machines via FireWire target disk mode
Authored by: sweyhrich on Oct 03, '03 07:10:23AM

I've also found that I can mount my PowerBook drives on my old Win98 computer via the firewire targe disk mode method. Both my OS X and OS 9 partitions showed up nicely in the Windows Explorer, and I was able to move files to and from the PowerBook. I do have a utility on the PC that allows it to read and write Mac files, so that likely would be necessary before any PC could do this.

Steven Weyhrich

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Connect machines via FireWire target disk mode ERROR
Authored by: lewray on Sep 27, '12 11:48:06AM

I am trying to do this with my crashed macbook and Copy files from the computer to my external hard drive trough another macbook. I can see and access my macs hard drive through the other computer but when i try to put in the files right on the external hard drive thats hooked up to the other computer it says "this file is read and write only" and wont copy anything...please help

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