Reinstalling Mac OS X without a DVD Drive – Target Disk Mode

Jun 14, 2009 by Dan Taylor    23 Comments    Posted under: Productivity, Technology

One of the primary reasons that I switched to mac just over a year ago was the stability of the Operating System. While my mac’s been fine, and would most probably have kept on working just fine, I guess there’s still a bit of my windows mentality lurking around, as when I started noticing some, ‘huh? what’s that all about?’ errors over the past few weeks, I guess I naturally reverted to the be all, end all solution – reinstall the OS. Fine and dandy, I’m quite familiar with the process via windows, so how hard could redoing the Mac OS X really be?

It’s quite easy – provided your DVD optical drive still works.

I had the lucky happenstance to find out that mine is dead. I’m probably not going to have it fixed, as I’ve read estimates anywhere from $380 – $466, and to be honest, I rarely every use it. However, this does bring up an interesting quandary; how to reinstall the mac os x with a dead optical drive? Apple provides you with a copy of the OS on two DVDs. Ok, first thought – see if I can’t copy these DVD’s using my old PC, and then just use the .dmg’s directly from an external USB drive. Great. But hold up there bucko, as it turns out, Apple Macintosh computers, both laptops and desktops can only boot from firewire drives. Hmmm. Personally, I don’t own any firewire external harddrives, they’re all USB based. So there goes that solution out the window. So here I am thinking that I’m really screwed, and either going to have to pull the main harddrive and plunk it into a friends mac, and do the reinstall that way (a major pain in the ass as far as I see it), until I did a bit of further digging.

Target Disk Mode

Now while I don’t have a firewire drive handy, I did have a 6-pin firewire cable lying around that I use with an external soundcard. As it turns out, you can use a firewire cable to connect two macs, and it’s quite simple at that. Here’s how.

For the purpose of this example, and for simplicity, I’m going to call the MacBook (to be used as the target disk) Black, and the MacBook Pro (where we’ll be installing the new OS) Silver.

1. Make sure that Black is turned off, attached to the power supply, and all external devices are unplugged.
2. Connect the 6-pin Firewire cable to black. Silver does not need to be turned off.
3. Boot Black, and immediately hold down the T key. After a few seconds, you should see a large Firewire icon floating around the screen.
4. Black should now appear as an additional disk on Silver. If you’re like me and do NOT have harddrives displayed on the desktop, press cmd+shft+c to bring up you list of available disks.

Et voila! Black, just became the words most expensive external harddrive/cd/dvd burner/reader combo drive known to man. So far so good, however, we’ve not yet installed the OS. From here, things should be pretty straight forward, however I did have one minor, ‘will that work?’ moment which I’ll describe below.

Upon popping the OS X installation disk in, you’ll get an auto prompt asking what you want to do with it. Select install OSX. The computer (Silver) will then ask you to reboot to begin.

Leave the firewire cables connected, and upon reboot, Black should remain in target disk mode, while Silver will now pick up the install straight from Black. If all goes well, everything should proceed as if you’ve inserted the disk directly into Silver (and the drive works).

So we’re all set, right? Yes and No. If you take a look at that DVD package that came with your computer from Apple, you’ll notice that there are 2 disks. Everything is cooking along, the OS is pretty much installed, but now you’ve reached that crucial moment of ‘Please insert disk two’. Ok, no problem, I’ll just eject the disk from Black and carry on. Hold on there partner, as Black is now in target mode – how ya gonna eject that disk? Can’t do it from the OS, and the hardware button no longer functions. Remember, when in target disk mode, Black ceases to be a fully functional machine, but again, a rather expensive external HDD/DVD drive.

To solve this problem, I took a round about way of solving this, and since I couldn’t find this info anywhere else, I took my own guess at it. Throughout this entire process, DO NOT remove the 6 pin firewire cable.

1. Press and hold down the power button on Black until it shuts down
2. Press the power button again, and immediately press the eject button. This should pop the DVD out before target disk mode launches.
3. Press and hold the power button down again, until Black shuts down again.
4. Press the power button down again, and now quickly slip disk two into the dvd drive.

This will handle the problem of inserting disk two.

As much as I’d like to have a functioning DVD drive, from what I’ve read this isn’t an uncommon problem for MacBook’s, both standard and pro. I tend to leave my machine on 24/7, and reboot it generally once a week. It has occurred to me that the additional heat generated by this prolonged usage may have not been the best thing for an optical drive (some parts are made of plastic).

If you’ve fried, or in my case, melted your DVD optical drive, if you’ve got another mac handy, hopefully this guide has walked you through the steps of using it in target disk mode to regain the features/functions lost. Any questions? Leave ‘em in the comments below and I’ll respond ASAP.