Thursday, 21 July 2011

Make a bootable Mac OS X Lion USB Flash / Pen Drive

Following on from my post about making a bootable 10.7 Lion Install DVD, here's how to make a bootable USB flash drive.

You will need the following: -
  • A Mac
  • A copy of the Lion Installer App (available from the AppStore)
  • A USB Flash Drive / Pen Drive with 4.2GB (approx) of free space
    ** NOTE ** Unfortunately, this doesn't appear to quite fit on a 4GB Pen Drive, you may find differently but for me Disk Utility gave a 'Not enough space error' Anything above (eg. 8gb) should be fine.

    1 - Go to the Applications folder and right click (or Control-Click) on 'Install Mac OS X Lion' and select 'Show package contents'.

    2 - Navigate to the Contents > SharedSupport folder

    3 - Copy InstallESD.dmg to someplace (eg. your Desktop)

    4 - Open Utilities > Disk and click on your USB drive in the left pane.  Then click 'Partition'.

    5 - Enter a name for the partition and make sure the format is set to 'Mac OS Extended (Journaled)'.

    6 - Click 'Options' and choose 'GUID Partition Table' as the partioning scheme.

    7 - Click OK, then Apply, you will then have to confirm and authenticate you want to go ahead.  This will erase all data on your Flash drive!

    8 - Now click the restore tab, select (or drag) the copy of InstallESD.dmg you made earlier in the 'Source' box.

    9 - Drag your USB Flash drive in to the 'Destination' box and click Restore, again you may have to authenticate.

    10 - After a few minutes your USB Drive will be ready to do... How long really depends on the speed of your USB Drive, but most have faster Read speeds than Write and you only have to write it once.

    11 - To test your USB drive, you can either go to system prefrences > startup disk and select it there, then hit restart, or just hold down the Option / Alt key while you restart your computer.

    12 - Enjoy some peace of mind!

    Hope you find this useful, please make a donation if you do :)


    1. Please: how many times have you verified that the hacks — both to DVD and to removable USB flash drive — work repeatably and consistently for reinstallation (not first installation) to machines with FileVault 2 application of Core Storage full disk encryption (FDE), where both the EFI loginwindow (early boot process) and the launchd loginwindow are used?

      Following reinstallation using both types of hack: can all of the subset of 10.7 users, with prior authority to unlock the startup volume, continue to both unlock the volume and then login?

      How many other reinstallation configurations have you tested, or seen verified repeatably, by other people who offer or adopt these hacks? How many other Recovery OS routines that involve novel uses of EFI, that involve other novelties, have you tested, or seen tested by other people?

      Consider: Apple's approach — to deliveries of Lion on day one — involved offering, to the five thousand or so developers who attended WWDC 2011, routines that focused on download.

      To the best of my knowledge, none of those developers were offered removable media for Lion Recovery. 6th June … 20th July … maybe not a great deal of time to test what was seeded at WWDC and the two builds that followed.

      Now — so soon after day one — there may be good reasons for Apple not delivering a USB thumb drive. Apple states that Lion will be provided on a USB thumb drive in August.

      I applaud curiosity, experimentation and innovation but please, suggest caution alongside hacks that pre-empt Apple's provision. At least: before a reinstallation that experiments with a hacked Recovery OS, comprehensive Time Machine or bootable backups.

      Thank you

    2. Well.. I don't really think this is a hack, we're using apple tools to put an Apple installer on a different media.

      As for FileVault, I don't know and would recommend anyone who uses it tests they can still access their files after a critical event before relying on this process.

    3. Thank you for the speedy response!

      For clarity: what's written to the removable media is only a part — not the whole — of the .app that is recommended for installation.

      We can not assume that all uses of that part will work as expected without the whole.

      Amongst the considerations: the disk identifier for the fixed hidden Apple_Boot 'Recovery HD' partition that arises from most first installations of 10.7. The Recovery OS is only a part of this partition.

      Consider also the disk identifier that may be expected for the volume from which the Recovery OS normally starts. (Not the same identifier as for the Recovery HD partition.)

      Now: introduce to mix a non-fixed medium (home-made DVD, home-made USB flash drive, whatever), with a volume name matching something expected by the system, with a different disk identifier. And so on … 

      … let the fun and experimentation begin! I'm pleased to note that most people report success with their experiments but these are very, very early days.


      Concerning FileVault, Macworld made a predictive recommendation to disable FileVault 1 home directories in Snow Leopard before upgrading to Lion. I disagree with that particular Macworld recommendation:

      Assume that for security and peace of mind, those who rushed to follow the Macworld recommendation will rush to enable FileVault 2.


      Defocusing from FileVault, my concern — and it's not directed at you alone — is that sooner or later we'll see people suffer in unexpected ways as a result of straying from Apple's recommended approaches to installing and reinstalling the first release of 10.7.

      The questions in my opening comment are questions that I would love to see answered by anyone who has test results. I should steer people to Apple Support Communities for 10.7 Lion —

      — and the 'Installation and Setup' category.

      Thanks again

    4. Thinking not only of FileVault 2 in version 10.7 of Lion — encouraging people to consider other environments, which previous hackers without the Apple infrastructure might have overlooked whilst testing — I have posted to my microblog.

      This first release of Lion aside: I do take a very positive view of non-malicious hacking, as has been done with Apple's software over the years, when the outcomes are positive. Some work by colleagues in my area:

      • Flowers, Stephen (2007) From Outlaws to Trusted Partners in: IRNOP VIII Project Research Conference, 19–21 Sep 2007, Brighton, UK

      • hacker innovation in the open access repository at University of Brighton

      — more recent work is in progress, if any reader would like to be put in touch with an expert please post to my microblog or contact CENTRIM.

      Thanks again for the considerate response to my first comment and — please — keep up the great work on positive improvements to iCal and Address Book!

      Best regards

    5. Hey,Some wonderful insights here. Great job and perhaps when I have more time, I will come back and read some more of your post.Thanks for sharing this information.

      USB Pen Drives

    6. Followed procedures as outlined. But USB drive appears on reinstall as LOCKED and can't use. How do you get drive unlocked? Thanks in advance.

    7. All 12 steps are handy and easy to do.I think this is one of the easiest post where user can learn how to make bootable pen drive in MAC os.Thanks for sharing among with us.
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    8. hi...Im student from Informatics engineering nice article,
      thanks for sharing :)

    9. Thanks for review, it was excellent and very informative.
      thank you :)