Installing Snow Leopard onto an External Hard Drive

By Dan Hinckley

61 responses. »

When new versions of an operating system are released, its not uncommon to want to test out how the new software will work with your hardware, software, and data. The worst thing to experience is when your “upgrade” becomes a “downgrade” because none of your data is accessible or software available.

Apple recently released Snow Leopard and we walked readers through how to install snow leopard from a USB Drive. Now we’ll explain the steps on how to install snow leopard onto an External Hard Drive so users can test out the new OS X 10.6 without risking the potential negative impacts of an upgrade on their Leopard Installation.

Installing OS X Snow Leopard on an External Hard Drive

The steps to install Snow Leopard onto an external hard drive are very similar to the steps of booting OS X from a USB drive. In fact, if you have a large enough USB flash drive, you can use these same steps to install Snow Leopard on to it. This 128 GB USB Flash Drive can service just as well as a normal External Hard Drive, and may even run a bit faster than your typical HD.

  1. Insert the OS X 10.6 Snow Leopard DVD into your Mac, or boot into the USB Snow Leopard Installation we described in an earlier post.
  2. Open system preferences from the menu bar, select start up disks and then the OS X 10.6 Snow Leopard Install DVD. Click the restart button to start the installation process
  3. After your computer restarts continue through the introduction and agreement pages
  4. The External Hard Drive won’t currently be an option for installation so we’ll need to use Disk Utility to make some configuration changes. Select Utility from the Menu Bar to access Disk Utility.
  5. Once Disk Utility opens, select the External Hard Drive you’d like to install Snow Leopard onto and then Select Partition. From here select 1 Partition and then click Options. To allow the Mac to boot from the external hard drive, the drive must be setup with a GUID Partition Table. Select GUID.
  6. To make sure that you don’t mistake the External Drive for your normal Hard Drive, be sure to name the Volume something like “Snow Leopard”. Apply the changes and continue to the next step
  7. Exit DisK Utility and the installation window will return asking which volume you’d like to install snow leopard onto. Select the External Hard Drive that we partitioned with GUID (Named Snow Leopard) to continue the installation. Follow the instruction until the installation is complete.

The installation requires at least 8.1gb of space, so a normal 8gb flash drive won’t work. If you’re using an External Hard Drive you can install the complete installation (11gb). If this isn’t enough space be sure to customize the installation and remove printer settings and extra languages.

Snow Leopard Installation Time

Once the installation to my External Hard Drive started, it took 30 minutes to complete. The total install time including setting up the External Hard Drive as a GUID bootable device took close to 40 minutes.

This time depends completely on your computer settings and hard drive speeds.

Snow Leopard Installation Problems

I didn’t have any problems installing Snow Leopard to an External Hard Drive with the steps listed above, however after the installation completed it tried to reboot to the external hard drive on its own. It got stuck during the restart but powering off the Mac and starting again holding down alt (option) allowed me to select and boot from the hard drive.

Let us know what problems you’re having with your installation efforts and Maciverse will do our best to Help.

External Hard Drive Snow Leopard Speed

I’ll be the first to admit that I was amazed at the speed of the OS on the External Hard Drive. I expected Snow Leopard to run slower than the native hard drive but that wasn’t the case. Safari opened quickly, finder also was zippy, and the dock functioned without any speed issues. Moving files around and creating video with Quicktime X worked flawlessly.

It functioned so well that I’ve decided to do a fresh install on to my internal hard drive on my Mac. I’ll backup the data on the drive and follow the steps listed above but will select my internal hard drive as the volume.

About Dan Hinckley
Dan Hinckley is an experienced Mac user who converted to Apple products when they introduced them on Intel Processors. He loves helping others get more out of their devices! Subscribe to to get the latest from Dan and the Maciverse Team!! Find out more about Dan:

61 Responses so far.

  1. Matt

    September 22, 2009 at 9:48 pm

    Yep it works! However you don't really need to restart to the install DVD. I was able to choose a pre-GUID-partitioned USB volume and get it detected after starting the Sno Leo installer from the DVD. (I partitioned it using my MacBook Pro's Disk Utility prior to the install.)

    It did restart my Mac during the installation process about 25% through it…not sure why. But it took about 40 mins total.

    Thanks to Apple for finally giving us the ability to do this again! It helps to be able to create a backup volume with an OS to boot from in an emergency!

  2. A Snow Leopard Is Coming! « BeginnerPC : Tips , Tricks & Tutorials

    September 26, 2009 at 8:28 am

    [...] Installing Snow Leopard onto an External Hard Drive How to ins [...]

  3. Dylan

    September 29, 2009 at 10:27 am

    Does this work for a g5 imac. my imac has the GUID partition option but i still don't know if it will work.

  4. Dan

    September 29, 2009 at 10:44 am

    Dylan – Snow Leopard will not work with a G5 iMac.

  5. Dorian

    November 23, 2009 at 7:23 am

    Thanks for this tutorial! Can I just put the the external drive into my MBP and use it as the internal HD if everything works fine with Snow Leopard?

  6. Dan

    November 23, 2009 at 10:14 am

    Dorian, yes. If you install onto an external HD, you can boot into it and run OS X from it, accessing your internal HD should still be available.

  7. Rainer

    December 1, 2009 at 4:37 am

    Hi Dan, I think that's not what Dorian meant and what I am interested in. Is it possible to install Snow Leopard to an external 2,5" drive connected to the Mac by USB and then take that external drive out of its box and use it as internal in the Macbook?

    From a hardware point of view it is possible, but from software? Will it boot or will the boot process look at the wrong location? Are there maybe paths hardcoded to the external location (USB).

  8. Dan

    December 2, 2009 at 1:47 am

    That should work. I believe I've done so successfully in the past but can't recall specifically. There shouldn't be a problem. Let us know if you try it out.

    • Joshua

      December 4, 2011 at 10:29 pm

      hey the speed of snow leopard on the External hard drive was pretty quick because the hard drive uses the processor on the computer you are running the external HD from because a hard drive doesn't contain a processor

  9. Michael

    December 3, 2009 at 1:27 am

    Two quick questions.

    1. If I install SL onto an external HD and then go to boot up my computer, will I get the option to select which OS I want to load? I'm interested in this option for several reasons such as using the external OS for software testing, etc.

    2. If I have the setup mentioned above (internal OS and External OS). Say I don't have the external OS connected, when I boot up my computer will it default to the internal OS and boot up automatically?

  10. Dan

    December 3, 2009 at 8:33 am

    Michael – Hold down the option key (alt) during boot up and Macs will allow to select which device you want to boot into. For stability purposes, you probably want to leave your internal HD as the default boot drive, and just hold down option when you want to boot into the external drive.

  11. graham

    December 27, 2009 at 3:14 pm

    have had major issues installing SL on to two diff tiger machines – black macbook just crashes, mac mini seems to work but after installing onto external usb drive reboot just hangs (grey screen spinning wheel) on macmini and crashes macbook. Any thoughts??

    • dana

      November 8, 2012 at 11:47 am

      update before rebooting

  12. Toby

    January 3, 2010 at 10:12 pm

    I have a Macbook Pro 5,5 and I am about to wipe the whole disk and install Ubuntu 9.10 instead and I am not interested in OSX.

    Would the above still work as a viable option to having Snow Leopard installed in a ext hard drive so that I could boot the Macbook Pro into SL for any critical updates to the EFI? But be totally seperate to Ubuntu?

    • Dan

      January 5, 2010 at 12:12 pm

      I think theoretically it should work. IF you try it out and it does, let us know!

  13. Carlos

    January 9, 2010 at 8:49 am

    Can you still boot from the external HD into a non-mac pc like a regular windows pc that has an Intel processor and all the other requirements? Has anyone tried it yet??

  14. DC

    January 20, 2010 at 4:45 pm

    @Dan, i already have files stored on my ExHD named “DCHD”. When I go to partition(1 partition) is tells me that the DCHD will be erased with all files and replaced with Snow Leopard. I tried it with 2 partitions and same thing?? I cant delete my the files HD. Is there a way around this? thanx

  15. dan

    January 21, 2010 at 1:25 am

    DC – You'll need to copy the files off to another drive, make the partition, and then copy them back on to one of the drives… Unless someone else knows of a partition magic like software for the Mac?

  16. How to Increase Blog Traffic by Over 100% In 3 Days - Remarkablogger

    February 18, 2010 at 7:19 pm

    [...] articles are: Install OS X Snow Leopard From a USB Flash Drive, Snow Leopard Parental Controls, and Install Snow Leopard On an External USB Hard Drive. While not as sexy or glamorous as the more general articles, these longer-tail articles quickly [...]

  17. Anthony

    May 4, 2010 at 3:55 pm

    i have tried all the steps and my install hangs for hours. it says 30 minutes but after an hour the progress bar moves very little. any ideas as to why this is happening?

  18. Jake Brown

    June 10, 2010 at 8:16 pm

    I actually used this to install SL on a blank internal hard drive as my sisters MacBook hard drive was completely corrupt, it was clicking, beeping etc. Worked like a charm :) Thank you!

  19. Taking the Guesswork Out of Restoring Your Mac |

    July 1, 2010 at 1:10 pm

    [...] Installing Snow Leopard onto an External Hard Drive How to install snow leopard onto an External Hard Drive… [...]

  20. Danish

    July 29, 2010 at 11:59 pm

    Hi, i used the above step to install fresh snow leopard on my assembled PC (not mac hardware). After restoration of .dmg file to my newly created GUID 1 pertition on my USB HDD(Seagate 160GB) not booting from it. Even i tried with on of my friend 8GB pen drive but it took approx 2Hr to restore to pen drive and at the time of verifying it giving the error " Some read/write error on destination" ie. verification is failed. Please send me the solution for this to my mail id mention above as well as post on this site so other can take the benefit of the solution. Mac is amazing. I love it but want to use it….

    • Dan

      July 30, 2010 at 12:16 am

      The steps provided are only outlined to work with Mac hardware. Since PCs utilize BIOS you can't leverage the GUID partition and boot function in the same way.

  21. aaron

    October 19, 2010 at 9:24 pm

    my hdd got crashed and bought new hdd formatted it but wont format so i but it into a sata controller and format with another mac and install the os x externally. when i placed the hdd in iternally it couldn't boot.please what should i do?

  22. jak

    October 27, 2010 at 1:58 pm

    does this work for mac mini g4 1.25 Ghz

  23. Dan

    October 27, 2010 at 2:00 pm

    Jak – This is for intel macs only. It will not work with a G4.

  24. Mike

    November 1, 2010 at 6:31 am

    Using this method, would I also be able to install Parallels and Win7 on top of this? Seems like it would be possible in theory.

    My internal SSD is low on space and Win7 requires ~15GB. An external drive with SL+Parallels+Win7 would be sweet.

  25. Dan

    November 1, 2010 at 6:51 am

    @Mike – It should work just fine this way with Parallels and Win7.

  26. Increase Blog Traffic « Behind The Stage Blog

    December 6, 2010 at 11:29 pm

    [...] articles are: Install OS X Snow Leopard From a USB Flash Drive, Snow Leopard Parental Controls, and Install Snow Leopard On an External USB Hard Drive. While not as sexy or glamorous as the more general articles, these longer-tail articles quickly [...]

  27. Moh

    February 2, 2011 at 5:44 am

    i followed all the steps countless times..but when its time to install it takes a long time and then just before its about to gives me an error saying mac os x could not copy the necessary files
    plz help :(

    • Dan

      February 2, 2011 at 10:28 am

      We need more information. Size of the external HD, type, how you partitioned it, what model mac are you using, etc.

      • Moh

        February 2, 2011 at 8:38 pm

        i have a mac book 13" which was running mac os x 10.5.4. I have 200 GB WD hard disk and i partitioned it exactly the way you said to do it in the tutorial. My mac cd drive is broken and some problems happened with the software so i had to resort to this method but its not working when i install it.

        • Dan

          February 2, 2011 at 10:59 pm

          Are you using a retail snow leopard DVD or the disks that came with your Macbook? If its the disc from your macbook it may have problems with the external HD. I've not had any trouble with retail snow leopard DVDs for this process.

          • Moh

            February 2, 2011 at 11:19 pm

            ya its a retail copy of snow leopard…im gonna try something else ima install snow leopard from another mac on to the hard disk and then find a way to install it on to my mac book.

            thnx for your help

  28. kbb

    February 14, 2011 at 12:56 pm

    Can you install also install programs onto the external drive once you boot from it?

    • kbb

      February 14, 2011 at 12:57 pm

      sigh – Can you also install*

  29. Mike see

    March 20, 2011 at 7:51 pm

    Iv'e been trying to install SL 10.6.3 onto a new clean internal HDD but the install stalls and says installation failure, unable to install support files. The SL I have is the $29 'upgrade' DVD, is that my problem? Or can I use your external USB method with my SL dvd?


    April 2, 2011 at 10:37 am

    After I install Snow Leopard onto an external HD, is there a way to configure things so I can plug it in to a PC and boot it up?

  31. Josh D

    June 7, 2011 at 2:32 pm

    During step 5, where is the "Select Partition"…I can't seem to find it???

  32. JMS

    December 8, 2011 at 3:40 pm

    I have a new MacBook Air, as well as a new Seagate External 500GB HD. I have tried a number of times to boot from the Snow Leopard 10.6 DVD in my external CD/DVD drive, so I could install Snow Leopard to the Seagate drive. It starts up and then, before anything comes up on the screen, the CD drive stops and nothing happens.

    Any ideas? Would very much appreciate any and all thoughts.


    • Dan

      December 8, 2011 at 4:16 pm

      Create a bootable USB drive first! or a partition of that external HD that has the Snow Leopard install files on it.. Then install from one of those.

  33. Sara-deva

    January 15, 2012 at 10:00 pm

    i have a mac book pro mid 2010 core i5, i install snow lep 10.6.3 on an external…runs smoothly for about 2weeks maybe….then it wont startup…the spinning wheel freezes…and the external hdd also seems not to work when the spiining wheel stuck…what the problem? i uses the snow lep 10.6.3 dvd that came with my macbook, is this the problem here?

    because i uses the same dvd and install it on my friend macbook, it works, no freeze, no bugs for about 5months now!

  34. Sara-deva

    January 15, 2012 at 10:02 pm

    is that true that there are factory defects in the batch production of macbook pro mid 2010?

  35. upgrading to Lion – the golden rules! | Phil Stokes

    January 31, 2012 at 7:14 am

    [...] of these programs in your daily use, you’re going to need to upgrade those too or continue to run Snow Leopard on an external disk. Golden Rule No. 2: Buy an external disk and clone your current system to [...]

  36. how to turn a Lion into a (Snow) Leopard « Phil Stokes

    May 26, 2012 at 8:55 am

    [...] a look at How to Install Snow Leopard on an External Disk — If you’ve already got Lion on your internal, install SL on an external first. Try it out [...]

  37. Chase

    May 26, 2012 at 5:26 pm

    Hi. Firstly, thanks for writing this. It's brilliant.
    When the computer starts and I hold option, the flash drive isn't showing up. It comes up as soon as the computer restarts as it should, and all the contents for installation are there, and I can even choose to install like I would normally from the disc, but for some reason the installation gets about 10 minutes in and the computer restarts. I've tried to install it several times thinking it was restarting on its own, but the installation process starts over as well. When I went to look at the contents of the flash drive, it shows OS extended, but I've completely redone the process and selected (journaled) three times now. Any suggestions? The computer has never had any problems restarting before, nor has it had any other trouble since or before.
    Any help would be greatly appreciated. I know I am just being dumb and missing some detail.


    • Dan

      May 26, 2012 at 8:28 pm

      Did you make sure to format the USB drive as a GUID partition?

      • Chase

        May 26, 2012 at 11:46 pm

        Yes, sir, indeed.

      • Chase

        May 26, 2012 at 11:55 pm

        Also, now, as I open the flash drive upon restart, there is a file titled "boot.efi" with a lock on it. It wasn't there the first time and it disappears as I eject the flash drive and open it "fresh." The download continues without trouble until the prompt "installation will continue after youre computer restarts" shows and the computer restarts on its own. As the computer restarts, the installation doesn't continue on or boot from the flash drive as selected from the "startup disk" either. Thanks again for writing back.


  38. Maz

    June 4, 2012 at 9:18 am

    hi, I have followed your guide but when I select SL DVD and restart I get a message internal panic???? restart machine, i have only recently bought my macbook pro and it has Lion pre installed can you advise?

  39. Marsha

    June 12, 2012 at 11:46 am

    I've tried more than one way to install Snow Leopard on my intel MacBook Pro (2007). I just went through your steps and thought I had it finally nailed. My MBP recognizes it in Preferences > Startup Disk but doesn't boot into SL when I choose it as a startup disk or when I use the boot keys on startup. I'm now at a loss. Please advise.

    • Dan

      June 12, 2012 at 11:52 am

      Did you make sure to set the disk as GUID before you installed?

  40. Marsha

    June 12, 2012 at 11:51 am

    I'm using the 10.6.3 single Mac OS X Snow Leopard DVD purchased from Apple and my Mackbook Pro meets all the system requirements.

  41. John

    July 6, 2012 at 9:49 pm

    When partitioning the drive it would wipe my data right?

    • Dan

      July 6, 2012 at 10:01 pm

      It depends, often when you create a partition you're overwriting an old partition and it wipes your data. When creating this startup disk, its most likely that the process will overwrite your files and data.

  42. Alex

    August 9, 2012 at 12:39 pm

    Thanks for the guide, worked a treat! The only question I have is when your using / running SL from the external hard drive what is happening to the internal hard drive? Is it laying dormant until you boot from it or is it copying files you are processing on your EHD?

  43. socheat chan

    September 7, 2012 at 9:03 pm

    hi, my name Socheat Chan, today i problem with bootable from dvd and usb drive in mac PowerPc G4.
    i have PowerPc G4 Mac os x 10.4, i want to upgrade to snow leopard 10.6. i have try many way to upgrade it even boot from usb drive. it can boot from usb drive even i press option key but it stil not show me to boot from usb drive. does any one know different way with PowerPc G4 to boot from usb drive.

    Note: in my mac can not boot from dvd or cd even i try to reset by press alt-command-p-r

  44. Antonio

    January 15, 2013 at 1:20 pm

    Hi, I just want to know if the lowes pentdrive that I can use to install snow leopard is 128Gb, or can I used 32Gb or less… Thanks for your supprt!

  45. automatic litter box

    March 16, 2013 at 5:33 pm

    I loved as much as you will receive carried out right here.
    The sketch is tasteful, your authored material stylish. nonetheless, you command get got an shakiness over that you wish be delivering
    the following. unwell unquestionably come more formerly again since exactly the same nearly very often
    inside case you shield this hike.

Leave a Reply

Site powered by Go Fish Digital