Given that Fedora has made it so easy to put a live cd image onto a usb or other external drive to provide a bootable take anywhere OS.
First off, you'll need the Fedora Live CD or DVD iso image, they can be found on the Fedora home page http://fedoraproject.org/en/get-fedora
You'll also need to install some other packages available in the standard repos.
Install livecd-tools with your package manager.
Next you'll need to partition your drive, unless it is already partitioned as you want it. We'll assume from now on that your drive is on /dev/sdb and you will be installing into the first partition, /dev/sdb1
I've partitioned my external drive into two partitions, 1 ext3 partition that I'll put the live image. I've selected ext3 so I can have a partition that will respect file name case, file ownership and file permissions. I have the remainder as fat32 to provide compatibility with a wide range of OS's and devices.
So First check that the partition is marked as bootable using parted:
GNU Parted 1.8.8
Using /dev/sdb
Welcome to GNU Parted! Type 'help' to view a list of commands.
(parted) <b>print</b>
Model: WDC WD12 00BEVS-75LAT0 (scsi)
Disk /dev/sdb: 119GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos
Number Start End Size Type File system Flags
1 32.3kB 50.0GB 50.0GB primary ext3 <b>boot</b>
2 50.0GB 119GB 68.5GB primary fat32 lba
(parted)
If you do not have the boot flag set then issue the command:
This will make it bootable. Exit parted with quit
Now we're ready to write the iso image to the device, I'm using the --overlay-size-mb 4000 to allow the booted OS to persist any changes that are made. I've allowed 4000MB (4GB) for the overlay image.
To write to your device:
It should now be ready. To test your drive without having to reboot you can use qemu to run it in a virtual machine: