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Does anyone have a Terminal command-line recipe for making a new bootable USB flash drive for one of the new MacBook Air's? Is there a way to dd copy the USB boot device that comes in the box and make the new copy bootable? I'd like to make a new backup copy of the USB rescue device for my MBA, preferably on a much larger flash drive with room for a backup of some of my working directories.

Added:

And is it possible to make, not just a rescue drive, but a bootable USB drive that will boot a fully updated version of the OS (say 10.6.8 or later)? If so how on a MacBook Air 11, and how big a USB stick will this require?

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Which Air do you have? The larger one has an SD card slot, which can also be used as a boot drive. –  Dori Jan 29 '11 at 10:18
    
@Dori : MBA 11, smaller one with no SD slot. –  hotpaw2 Jan 29 '11 at 18:22
    
Are you looking to move the OSX installer to a drive or just have a second bootable device. If the latter, simply format the USB drive and install OSX onto the drive. Update the software periodically and you are done. Moving the installer to the USB takes a little more effort. –  bmike Jun 27 '11 at 0:10
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4 Answers

up vote 9 down vote accepted
+50

Here is a simple recipe for making a USB version of the OS X installer + associated tools. (Migration Assistant, Disk Utility, Network Utility, Terminal (that auto mounts your internal drive as needed), Firmware Utility and Password Reset Utility.

1) Use Disk Utility backup/restore to image whatever Snow Leopard DVD you prefer onto a HFS+ formatted GUID USB drive. I usually first create a IMG of the DVD, but it should work in one shot. Watch for restore errors - you may need the Disk Utility menu command Images -> Scan images for restore... before restoring an IMG to the USB drive.

2) bless the USB drive by selecting it in Startup Disk or using the command line.

It's not that hard to make a bootable image and far more secure to DIY. It also avoids the need of downloading commercial software from the internet. Happy media shifting all!

If you simply want a bootable thumb drive, just install OSX onto that volume - turning off all the extras you may not need. You can have your USB on one side and the USB install disk on the other to make your bootable drive ensuring all the Air drivers are on your USB bootable drive (which is often an issue when using another install's image - sometimes the drivers are not all there on older builds of the OS)

The best trick I have when you don't have enough space on USB to create the final updated version is to stage the bootable image by install first to a 25G partition on an external hard drive.

You can finish installing with lots of free space on the HS, run all the updates newer than your installer (10.6.8 for example), make an admin account, install the tools and apps you need. At the end of the process, you then thin out the things you don't need. DaisyDisk or WhatSize will show you all the large files and libraries. You can safely get rid of a lot of iLife and the associated Application Support. WhatSize has many options to strip out unneeded files, localizations and PPC code. Once you have slimmed down the bootable image on the HD partition, use the trick below to get it on the USB drive. Leopard was a tight fit in 8G but Snow Leopard is lighter and doesn't need to diet as much.

Edit: Here are terminal commands for rolling your own installer like the (read-only) one that ships with current MacBook Air. I have a Snow Leopard DVD as /dev/disk5 and my USB is /dev/disk6. The man pages for diskutil and asr are helpful if you run into little gotchas or have different needs than a basic one partition drive.

$diskutil list
/dev/disk5
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:     Apple_partition_scheme                        *7.8 GB     disk5
   1:        Apple_partition_map                         30.7 KB    disk5s1
   2:         Apple_Driver_ATAPI                         1.0 GB     disk5s2
   3:                  Apple_HFS Mac OS X Install DVD    6.7 GB     disk5s3
/dev/disk6
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:                                                   *8.5 GB     disk6
$diskutil partitionDisk disk6 GPT HFS+ MacUSB 100%
Started partitioning on disk6
Unmounting disk
Creating partition map
Waiting for disks to reappear
Formatting disk6s2 as Mac OS Extended with name MacUSB
Finished partitioning on disk6
/dev/disk6
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *8.5 GB     disk6
   1:                        EFI                         209.7 MB   disk6s1
   2:                  Apple_HFS MacUSB                  8.2 GB     disk6s2
$sudo asr restore --source /dev/disk5s3 --target /dev/disk6s2 --erase
    Validating target...done
    Validating source...done
    Erase contents of /dev/disk6s2 (/Volumes/MacUSB)? [ny]: y
    Validating sizes...done
    Restoring  ....10....20....30....40....50....60....70....80....90....100
    Verifying  ....10....20....30....40....50....60....70....80....90....100
    Remounting target volume...done
$sudo bless --mount /Volumes/Mac\ OS\ X\ Install\ DVD\ 1 --setBoot

Note that the USB drive was renamed to be the same as the installer and the mount point in /Volumes has a space and a 1 tacked on the end.

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The current MacBook Air comes with a USB restore device, not a DVD. Does this make a difference? Also, is there a recipe to create a USB drive that can boot to one's fully updated 10.6.8 (or soon 10.7.x) OS? –  hotpaw2 Jun 26 '11 at 20:18
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No - the DVD and USB are equivalent read only devices. To "bake in" updates to the installer packages, you have to be able to parse/edit installer packages and read/edit/correct the pre-install and post-install scripts. It's much faster (& safer) to just store the combo updater on the device and run that later or use DeployStudio to snap a version of the installed software for distribution. It's a great idea, just more work than you might guess in general. 10.7 all bets are off since it will use the app store to validate a purchase and wants to install over SL only as it's currently described –  bmike Jun 27 '11 at 0:27
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dd makes a byte-for-byte copy of a disk so wouldn't really fit what you're trying to do. For example, if you used dd to copy your current USB key to a new bigger USB key, the additional space on that new USB key would not be usable because dd copies the partition table, not just the data.

Why not just keep your backups on an external drive. Then you could boot off your rescue USB disk and have your data saved on another external drive.

EDIT

Here's a method of at least cloning your boot disk from discussions.apple.com which seems to have worked for several people

  1. Get an 8GB USB stick and format it for a boot disk (partition it with GUID option and (Mac OS X extended (journaled)).
  2. Insert the Apple USB stick also. There is a invisible file at the root you need to mount on the desktop called MacOSX.dmg. You can use a utility such as Onyx or use the terminal with the open command to mount it.
  3. Use carbon copy cloner to clone the mounted "Mac OS X Installer Image" to the new USB stick
  4. Unmount the "Mac OS X Installer Image"
  5. Use carbon copy cloner to then clone the Apple USB stick to the new USB stick. Select the delete exiting files. Steps 2 - 4 are necessary because if you just clone the Apple USB stick the new USB stick won't be bootable.
  6. After this finishes you will now have a bootable copy. You can then also use Disk Utility to create a disk image of the new copy.

Helpful hints:

To allow you to view hidden files, in terminal run this command: defaults write com.apple.Finder AppleShowAllFiles TRUE (hit Enter after each command)

then: killall Finder

Afterwards, to hide hidden files again, go back to Terminal :

defaults write com.apple.Finder AppleShowAllFiles FALSE

then: killall Finder

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Carrying around the original rescue drive would be one more small device to lose. The copy is to be the backup of the original. –  hotpaw2 Jan 28 '11 at 23:15
    
New content noted. How can all this be done from the command-line? What does the cloner do that a cp does not? Will a dd to a similar sized flash drive do the same? –  hotpaw2 Jan 28 '11 at 23:37
    
@hotpaw2 - I don't know what would happen if you used cp to be honest but I'd expect dd would allow you to make an exact copy if you bought a USB key of the same size. the dd command should be dd if=/path/to/olddrive of=/path/to/newdrive bs=100M. This wouldn't allow you to store additional data on it though. Make sure you don't get if and of the wrong way round or you'll wipe your boot disk. –  conorgriffin Jan 28 '11 at 23:43
    
Correction, I think that boot disk is read-only so you may not wipe it but it's still important to get if and of in the right order in case –  conorgriffin Feb 6 '11 at 4:26
    
asr is a bit smarter about blessing a bootable volume and HFS than dd or cp and more likely to work with metadata, hfs compression and other nice things to have on limited storage space... –  bmike Jun 27 '11 at 15:34
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Just restored my flash stick with windows utility as described here http://osxdaily.com/2011/07/04/format-the-macbook-air-usb-restore-key/

link for utility http://www.sendspace.com/file/xek3yk

don't try to do this through the Virtual Box, use native Win7

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OK, it is Very easy to do if you can get your hands on the myriad of "ISO" OS X installers that make their way onto the internet shortly after any release.. or create an image your Installer disk yourself.... and simply restore it onto a separate partition of your USB flash drive.. all in good ole' Disk Utility...

they key is... DO NOT insert the *.dmg or *.iso file into the SOURCE box. Instead, INSERT THE VOLUME from the mounted image onto the source box in Disk Utility "Restore".

The only reason to use DD is if you are doing some crazy custom ISO nonsense, trying to fit the installer onto a 4GB stick.. This is how I made a 4GB rescue drive that I still use to this day "Snow Leo 911", it rocks... but if you've got room to spare... just partition that baby up and you'll be good to go.

Here's a pretty good write up of a similar approach. Cheers!

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Even if it were OK to repackage snow leopard and allow it to be downloaded by unlicensed people, I wouldn't trust someone that includes 40 paid software titles along with Snow Leopard in Snow Leo 911. It's not hard to image your legal copy of SL and bless the resulting image. –  bmike Jun 26 '11 at 19:50
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how about voting on my answer to his question.... a short & simple solution to his initial problem.. and why the more complicated solution he had initially considered was now proabably unneccesary... until recetly such maneuvers were all-but-necessary in order to "home-bake" a minimal and portable set of troubleshooting tools - which generally (still) is something not available through strictly conventional "means"... i referenced experience with these same problems and solutions. aka reality. his question wasn't a RFP for paranoid diatribes re: preferred diagnostic tools.. –  alex gray Jun 26 '11 at 20:58
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@bmike oh i see see... you also aswered the question... after me... WITH MY ANSWER!! you're shady man. –  alex gray Jun 26 '11 at 21:02
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Alex - If you look, I'm trying to show a recipe for making "cake" instead of downloading one that's already baked. If you feel that's shady (or by inference, me), you are welcome to that opinion. I do hope you stick around and participate since you obviously have some deep knowledge based on all of your answers here so far, and you might even be really nice in person. My skin is thick, so call me any names you want if you feel it helps you or the site. Editing away the meat of your answer wasn't something I would do, so I posted. I respect your voice even if I disagree with some of it. –  bmike Jun 27 '11 at 0:23
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