Creating a Bootable USB on a Mac for Flashing The BIOS on an HP N40L Microserver

I thought I would write a few words on this to hopefully save some other Mac users some time. I had to try so many times to get this to work.

I recently bought an HP N40L Microserver and I wanted to flash the BIOS to an unofficial version which enables more features (like AHCI full-speed SATA on all available ports – configure this as shown here). There are a variety of ways to do this, but seeing as the model I was working with didn’t have a CD drive, I wanted to boot FreeDOS off of a USB.

After various problems with Unetbootin, I discovered that it doesn’t actually create the boot image properly on a Mac. Bizarre.

What we’ll do is simply download a FreeDOS image prepared by someone else and then dd it to the device.

The image I used is FreeDOS 1.1 and I found it here. Download this and unarchive it. Whilst it’s downloading, take your USB device and format it to FAT32 in Disk Utility. Now go to Terminal and type diskutil list. You should see output similar to the following:

Terminal Screenshot

Here you can see that that I have already formatted the disk and titled it FREEDOS. My disk identifier is disk2s1. Yours will be something similar, you must work out what it is.

Unmount (read: not eject) the disk you want to use. For example, I used diskutil unmount /dev/disk2s1 – perhaps you would use diskutil unmount /dev/disk3s1. Word of caution: Don’t try and use a drive with multiple partitions. They will get destroyed.

Now that the drive is available for our exclusive use, fire up dd to copy across FreeDOS image that you downloaded onto the USB stick using this command: dd if=/path/to/image/FreeDOS-1.1-USB-Boot.img of=/dev/diskX where “X” = the disk identifier (2 and 3 respectively in the above example. After just less than a minute your new bootable USB should be complete (and automatically re-mounted)!

Simply download the unofficial BIOS from here (I simply removed two unneccessary files from the original, it still contains the latest modded HP BIOS), unzip it, and copy it on to the root of the USB drive.

Now stick it in the machine, fire it up, and simply type flash.bat at the DOS command prompt. Voilà.

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