In this Linux install tooling tutorial we will take a look how to create a bootable usb key with CentOS 6.5 (and higher) or CentOS 7. We have also add how to create a bootable CentOS 7 USB key from Mac OSX.
From a Linux System
To create a bootable CentOS 7 USB key you need an CentOS DVD image and an USB key that has at least 4.2 gigabytes of space.
The starting from CentOS 6.5 (or higher) you can install from USB keys by simply transferring the desired ISO using the dd command line utility. For instance using the following command:
dd if=CentOS-7.0-1406-x86_64-DVD.iso of=/dev/sdb
note: of course, you'll need to make sure that the output device (of=) is the USB key!
You can use exactly the same method for CentOS 7.
Note: the CentOS 7 installer image has a special partitioning which, as of (July) 2014, most Windows tools do NOT transfer correctly leading to undefined behaviour when booting from the USB key. So use an other Linux partition (or vm) or a Mac OSX machine to create your bootable USB key.