USB thumb drives, MacOS and the MBR

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Missing operating system. I had a lot of fun with this error message these days.

Happened on my Dell Mini 10v, which I own since back in 2009. I bought that cute little netbook in the first place because you could hackintosh it into a small OS X device (Snow Leopard at that time). And – you didn’t have to buy a copy of windows alongside with it, the 10v was offered with Linux (Ubuntu Netbook Remix).

Long story short: What was acquired more or less as a plaything was in use for years, running different OS, and still is in use, whenever I need a Linux machine. Last install was Lubuntu 14.xx and at some point upgraded to 15.10, which is no LTS version and official support ended mid 2016. So I was thinking of a clean install of Lubuntu 16.04 LTS to get rid of some remains from tested software and have a supported system with some new features.

Preferred installation method for this machine, that has no optical drive, is a bootable USB thumb drive. There are plenty of tools to create a such a USB drive, like Startup Disk Creator on Linux or Unetbootin. The latter is available for Mac and Win as well.

Startup Disk Creator gave me an error message, saying that the bootloader could not be installed. I tried Unetbootin and it worked. But anytime when I booted my Dell Mini from that drive, it said “Missing operating system”.

I was a little confused as I tried 3 different USB drives and all brought up the same error. What went wrong?

It happens to be, that I use my thumb drives on different machines for different purposes, and in special occasions I format them with HFS+ or ext4. I knew, I had to revert them to FAT32 before using them as boot media. But although Disk Utility on the Mac said that they would use the Master Boot Record, I suspected that the problem was exactly there. I found that there is an easy solution to this and I’d like to share it with you. (There are more solutions, but I think this one is most straightforward.)

On a (Debian based) Linux machine, open a Terminal (Strg + Alt + T) and type the following commands to install a MBR on the thumb drive:

sudo apt-get update
sudo apt-get install mbr
sudo fdisk -l  (<- find out which is your USB drive)
sudo install-mbr /dev/sdx (<- replace x with your drives designation)

This worked for me. Install-mbr can of course be run with several options if you have a special configuration or problem. Refer to the manpages for further assistance.

Remark: Newer machines use EFI instead of BIOS and GUID instead of MBR, so this may not apply for a modern PC.