Making a bootable USB key from an .iso image on Mac OS X | Borgström
Here’s a very useful and detailed OS X Command Line Interface (CLI) solution for taking a bootable iso disc image and cloning it to a USB drive – though it should work great for any attached drive. I used it to take my fresh copy of Windows 7, back it up, and to then at a later date make a bootable USB Windows 7 installation thumb drive.
Thanks to evan.borgstrom.ca for the ace article.
This was WAY harder than it should’ve been to find all this info. All the info out there was either wrong, didn’t work or incomplete. I ended up having to read the source code comments from Michael Forrest’s USB Creator For OS X project to figure it all out. While his approach of doing it through a GUI is nice, OS X contains all the tools you need to do it from a terminal, which suits me just fine.
Hopefully this document will work its way up Google so other people will find it easier than I did.
Purpose
Just to make sure we’re all on the same page here, the purpose of this exercise is to take an ISO image that you’ve downloaded that contains a bootable filesystem intended to be burned onto a CDROM and instead put it on a USB key so that a machine with the ability to boot from USB keys can boot it the exact same as if it were a CDROM.
We’ll be doing most of this from a terminal, with the help of disk utility for some things.
Prepare the USB key
We’re going to wipe the partition structure on the USB key. WARNING! THIS WILL DESTROY ALL DATA ON THE KEY!
Open up Disk Utility (it’s in /Applications/Utilities/).
Now do the following:
- Select the USB key (select the root device, not its partitions)
- Select the partition section at the top
- Change the Scheme to 1 Partition
- Change the Format to Free Space
- Click Apply
You will get a confirmation dialog appear ensuring you really want to delete all data on the key, choose Partition.
Once it’s completed you can quit out of Disk Utility.
Preparing the ISO image
Now that our USB key is ready, we need to get our .iso image into a format that we can copy to it. Open up a Terminal (it too is in /Application/Utilities, and I’ll assume you know how to use the terminal)
Now, convert the image from a ISO to a Read/Write Universal Disk Image Format (or UDRW). Here I’m using the xbmc live repack ISO, but you can use anything else that’s an ISO file.
user[/Users/user/Downloads]: hdiutil convert -format UDRW -o xbmc-9.11-live-repack.img xbmc-9.11-live-repack.iso Reading XBMC_Live (Apple_ISO : 0)… ........................................................... Elapsed Time: 24.475s Speed: 20.0Mbytes/sec Savings: 0.0% created: /Users/evan/Downloads/xbmc-9.11-live-repack.img.dmg
Once completed this will create the .img file. The hdiutil function likes to append a .dmg suffix to the file so it will probably end up .img.dmg after conversion.
Copy the image to the USB key
We’re finally here. The easy part, actually copying the image to the USB key.
First run diskutil list to get a listing of the disks in your machine so you can identify the USB key. It will look like this:
user[/Users/user/Downloads]: diskutil list /dev/disk0 #: TYPE NAME SIZE IDENTIFIER 0: GUID_partition_scheme *250.1 GB disk0 1: EFI 209.7 MB disk0s1 2: Apple_HFS Macintosh HD 249.7 GB disk0s2 /dev/disk1 #: TYPE NAME SIZE IDENTIFIER 0: *1.0 GB disk1
Here mine’s /dev/disk1.
Next we use the dd command to copy the image over.
user[/Users/user/Downloads]: dd if=./xbmc-9.11-live-repack.img.dmg of=/dev/disk1
On the command line we specify the Input File using if= and the Output File using of= and dd will copy the data from input to output, block by block. Note: the copy of the data here takes a LONG time…. Patience is a virtue.
Once it’s completed you can exit Terminal and remove the USB key from your OS X machine, it should now be able to bootup your ISO on another machine.
