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.
The purpose of doing this is mainly to ensure that the USB key is in a consistent known state and also to ensure that any volumes are not mounted by OS X. It is not required and you can skip it if you’d rather just unmount the volumes yourself.
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.
(#503:14u:0s) evan@8thwonder[/Users/evan/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:
(#504:14u:0s) evan@8thwonder[/Users/evan/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.
We want to use the RAW disk device so that our copy will happen much faster because the RAW disk device provides unbuffered access to the device (See this Apple mailing list post for more info). This is accomplished by simply prepending ‘r’ to the device so that /dev/disk1 is going to become /dev/rdisk1
Next we use the dd command to copy the image over.
(#506:14u:0s) evan@8thwonder[/Users/evan/Downloads]: dd if=./xbmc-9.11-live-repack.img.dmg of=/dev/rdisk1 bs=1m
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.
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.
NOTE: I wish I could take a credit for this, but I can't, here is the source.
Why not dd the ISO...? Should work as
dd if=/Users/username/Downloads/w8.iso of=/dev/sdX
with images, some people try to specify a partition # where really you should do the disc so it acts as a udf volume. Also, please clarify "didn't work", meaning they did not boot or writing the image to USB failed...? – nerdwaller – 2012-11-25T18:08:22.623Besides using dd, also ensure the partition has the boot flag set. – Karan – 2012-11-25T19:07:31.993
dd
ing the ISO didn't help. I am on OS X and disks there are referred to as/dev/diskX
and I wasn't specifying a partition number. Didn't work means didn't boot. All commands report that they are successful, but the disk can't be mounted. Booted up an Ubuntu Live USB and GParted says that there isn't a partition table on the drive. Weird. – duci9y – 2012-11-25T20:32:04.850You should be able to use pretty much any tool to place the iso on the thumbdrive. Since you have a Windows installation I would use the Windows 7 tool that exactly this just on a Windows 8 iso. – Ramhound – 2012-11-27T19:36:16.343
@duci9y Yes, there would not be any partition table shown on the drive after dd, it would look like a UDF volume (similar to a CD). – nerdwaller – 2012-11-28T02:35:03.373
@Ramhound I know about that tool, but the thing is, I don’t have a Windows installation! – duci9y – 2012-11-28T13:15:42.983
@nerdwaller But as there’s no partition table, I can’t install a boot loader, so it doesn’t boot. – duci9y – 2012-11-28T13:16:33.527
@duci9y That's odd, typically it wouldn't be required if it looks like a CD (which has the autorun functionality built in). You know anyone with an external disc drive, or have a friend with Windows? Other option would be to install VirtualBox and mount the USB into the VM, then use the USB Creator tool from MS and then you should be well on your way. – nerdwaller – 2012-11-28T13:23:14.157
Virtualisation is not an option. My Air has a processor without virtualisation support, and I am travelling right now, so I don’t even have friends here. – duci9y – 2012-11-28T13:33:35.530
@duci9y - Why are you trying to use a beta version of Windows 8? I figured you were trying to update Customer Preview to the RTM build. – Ramhound – 2012-11-28T14:40:05.613
I want to try Windows out. I did not buy it. The most legal thing was to download a Consumer Preview. – duci9y – 2012-11-28T16:23:27.067
@duci9y - You can use Windows 8 Enterprise Trial which has a 90 day time limit. You cannot expect us to help you with a beta build of a released product. – Ramhound – 2012-11-28T20:42:04.937