Building a USB from ISO on Mac

Hi all,

I lost a disk array recently and have tried to replace it with some old hardware and FreeNAS.  My hardware - an old R710 would not boot to CD or DVD at all.  So I had to put the software on USB.  I normally use some nice software called UNetbootin to do that but for whatever reason it would not work with FreeNAS.  So I had to do it with my Mac but that was new to me so after I worked it out I thought to record it here.

So plug your USB stick into your Mac.

Use the following command to locate your USB.

diskutil list

The list disk is one that matches the size of my USB and the partition type.  So that is what we need to remember - /dev/disk3.

Next we need to dismount the partition(s) on the USB so we can work with the USB. So use the following command to dismount the partitions.

diskutil unmountDisk /dev/disk3

Now that we can work with the memory stick we should change to where our ISO is.  In my case it is in the Downloads folder.

Once there we can use the following command to burn the ISO to USB.

dd if=NexentaStor- of=/dev/rdisk3 bs=64k

We can see above where I had a permissions issues so did the sudo command. The image was burned into the USB so we could test it out now. Also, it is not an error that used /dev/rdisk3, the extra r is important.

I learned how to do this via this information. It is important to understand that this may not work with all software.  I have used it with FreeNAS successfully and will update this article as I use it for other things.


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