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


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

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.

15 Responses


  • farmergeddon // // Reply

    Im trying this now from an imac installing to a macbook. At the change over point, the imac booted as normal, and a device removal arrear appeared om the macbook. I switched to disk two an relaunched into target disk mode and it seems to be carrying on ok.:) thankyou

  • Philip // // Reply

    Look, you’re the best. How I wish the world is like this where people like you will fill it.

    Thanks so much. It worked for me.

  • Adrian O'Connor // // Reply

    I’m pretty sure that the only-boot-from-FW disk is a very old, legacy limitation that hasn’t applied for a long time now. You can definitely boot from USB disks on semi-modern hardware (for example, I’ve booted my 2007 iMac and 2008 MacBook Pro from USB many times, with my super-duper backup disks). There is a trick though — when you partition the USB disk, you MUST make set it to have a ‘GUID’ partition table, not MBR. Most disks you buy will be MBR, so you have to re-partition them before you can boot them. The Firewire thing is clever, but it’d probably save you a lot of time to just write the DMG to a big USB memory stick and boot from that instead.

  • Paulo // // Reply

    do i really have to use firewire? isn’t some “dd if=/dev/sda of=/dev/sdb bs=32M” enough? (replacing ‘sda’ and ‘sdb’ with the disk device names)

  • user // // Reply

    It’s easy to install PPC versions of OS X without a CD/DVD drive if you have an OS X disk image , like .iso or .dmg:
    1. Make second partition on your hard drive (4.7 size) with Disk Utility, just be sure you have 10+GB of free space. You will NOT lose any data.
    2. Mount .iso (.dmg) by double clicking
    4. Open Disk Utility go to Restore, then drag the MAC OS X to ‘destination’ and your second partition to the ‘Source’. enter passw
    5. Restart and hold alt (option) button
    you can do the same with the another mac by connecting the destination mac in the ‘target disk mode’

    • daniel // // Reply

      I tried doing what you suggested but when I plug it into my mac and open it from the restart screen using alt it opens to a message that says to restart the computer every time.

  • Diana // // Reply

    Thanks so much. I am overseas, my apple care is expired, my optical drive (which has never been used) was dead & my macbook pro needed repair. Thank goodness I have some iMacs around and this worked like a charm – except my sick laptop was the target computer & I accessed disk utility from “silver iMac” which allowed me to repair my disk! It was a terrifying but very rewarding experience when I saw “The volume Macintosh HD was repaired successfully!”

  • Raj // // Reply

    Hi, this did not work for me after the bit where you restart having inserted the osx install disc. It would halt at the grey apple screen. However, I booted from the osx cd by holding down ‘C’ and it worked

  • andi novianto // // Reply

    Thanks a lot. This is a very usefull information and it works like a charm. One thing to notice that in my experiment that it didn’t work using external dvd drive. For instance, I’m installing a macbookpro using dvd from my imac (imac as target disc). When using external dvd in my imac the install disc can’t be detected. but it works fine when using builtin dvd drive. So the dvd drive shouldn’t be external otherwise it won’t show up when i press option in my macbook while booting. Maybe … actually i can connect directly the external to my macbookpro, but i did it on purpose just to do some experiment to see myself how this target disk mode really work. Also if i don’t have the dvd drive, i can still install using .dmg file. So i need to create a 10Gb partition in my macbookpro (in target disk mode) using diskutility and then using ‘restore’ to do a raw copy the image of installaltion disc (.dmg or .iso) into that partition. Later on when boot , press option key and that partition will show up as a installation disc ready to use.

  • aim // // Reply

    Thank you for posting such a well written explanation for booting my laptop from my computer. One question before I start, would I have any issue using disk utilises when in installation mode to format my computer first? Really need to start the computer fresh! Thanks again! Amy.

  • Fintan // // Reply

    Great article Dan. I have two Imac”s and the newer one (about 2 years old) will not reboot, goes to the ? screen. Can I use your method to retrieve files from the newer Mac onto the older Mac and then install OSX ?
    Thanks,
    Fintan.

  • Steve // // Reply

    Thanks for the tips, worked great

  • MacGus // // Reply

    Great… this worked great.. and bring back a smile to my face. :) after corrupting original OSX I used your method above.. to bad we are not close (San Fco) other way the drinks will be on me. Blessings..

  • lilac2014 // // Reply

    Would you please indicate exactly what kind of firewire cable should I get? I have a macbook pro 15″ which superdrive no longer works and a macbook (white).

  • Dan // // Reply

    Hi Lilac. It really depends on what type of firewire port you have on your machine. You’ll have either a firewire 400 or 800. This image shows the difference: http://bit.ly/1cyiiMq, with an 800 on the left, and a 400 on the right.

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