Creating a bootable USB stick with Mac OS X in 10 easy steps

I heard a presentation about Intel’s new Linux distro for mobile Internet devices, called Moblin. Now I didn’t want to create a Live CD, but rather a “Live USB stick”, which would be so much easier than connecting an external DVD drive to my netbook (a MSI wind).

Until now I only had found a Windows solution for this, which required a physical Windows machine. Since I don’t have such a device, it was a bit of a dud. I did some more poking around with Google, and found a Dutch description of how one might do this with Mac OS X sec, so without any additional software.

Of course, you need to format your USB stick so, that both Mac OS X and a PC can read it, in other words, use the lowest common denominator, also known as FAT32 (or: MS-DOS format). That wasn’t included in the instruction, because it is so obvious. However, one can’t assume someone landing on this page to know of such things, so I added that to the instruction (sort of).

Prerequisites

Logged in as administrator

Because you are going to use the sudo command, you have to be logged in as an administrator. A non-administrative account will not work.

Formatted as FAT32

Start the application Disk Utility (located in the folder /Applications/Utilities/ of your Macintosh HD volume), stick in your USB stick, and format it as FAT32. If you don’t know how to do that, read this instruction on the AppleInsider forum, or do a Google search on FAT32 disk utility.

The Ten Steps

Here are the steps in words:

1. Download the .iso file. This also can be an .img file. Let’s call it moblin.img.
2. Rename the .iso file to .dmg. In our case, rename moblin.img to moblin.dmg.
3. Right-click on the .dmg file and select Get Info. Write down the full path name as mentioned in the dialog box. We will need that for step 9.
4. Start a Terminal window. The Terminal application is located in the folder /Applications/Utilities/ of your Macintosh HD volume.
5. In the Terminal window, type:
   diskutil list
   and press the Enter key. Now a list of your storage devices is displayed in the Terminal window, underneath what you typed earlier.
6. Put the USB stick in the USB port of your Mac.
7. In the Terminal window, type again:
   diskutil list
   and press the Enter key. Now you see the same list, but with an extra storage device. The location of that device has the format /dev/diskN, where N is a number. In my case it was /dev/disk4. Write that down.
8. In Terminal, type
   diskutil unmountDisk /dev/diskN
   and press the Enter key. Use the N from step 7. This will unmount the USB stick (it will disappear from your desktop).
9. In Terminal, type
   sudo dd if=/path/to/file.dmg of=/dev/diskN bs=1m
   and press the Enter key, where /path/to/file.dmg is the full path from step 3, and /dev/diskN from step 7. You will be asked to enter a password. This is why you must be logged in as an administrator, a non-administrator does not have to privileges to perform this operation. This operation takes quite a while (10 minutes in my case). Be patient and let it do its thing.
10. In Terminal, type
    diskutil eject /dev/diskN
    and press the Enter key. Again N is the number we established in step 7.

Now you can take out your USB stick and use it to boot your netbook. Booting your netbook from a USB stick is a whole other matter, which I won’t discuss here.

That is all.

(January 11, 2010: I noticed that the Terminal command is “unmountDisk” and not “unmount” as was written in an earlier version of this post. Sorry for any inconvenience.)