how to setup a usb key to install centos

steps

info

 starting with centos 6.5
 you can install from usb keys
 by simply transferring the desired iso using dd

demo

 $ sudo dd if=CentOS-6.5-x86_64-bin-DVD1.iso of=/dev/sdb

fixed

dd: /Volumes/gree2: Is a directory

info

 $ dd if=CentOS-6.5-x86_64-bin-DVD1.iso of=/Volumes/gree2
 dd: /Volumes/gree2: Is a directory

check with mount

 $ mount
 /dev/disk1 on / (hfs, local, journaled)
 devfs on /dev (devfs, local, nobrowse)
 map -hosts on /net (autofs, nosuid, automounted, nobrowse)
 map auto_home on /home (autofs, automounted, nobrowse)
 /dev/disk2s4 on /Volumes/gree2 (msdos, local, nodev, nosuid, noowners)

fixed

 use /dev/disk2s4 instead of /Volumes/grees

dd: /dev/disk2s4: Resource busy

info

 $ sudo dd if=CentOS-6.5-x86_64-bin-DVD1.iso of=/dev/disk2s4
 Password:
 dd: /dev/disk2s4: Resource busy

check with df

 $ df -h
 Filesystem      Size   Used  Avail Capacity iused      ifree %iused  Mounted on
 /dev/disk1     233Gi  165Gi   67Gi    72% 2421155 4292546124    0%   /
 devfs          185Ki  185Ki    0Bi   100%     640          0  100%   /dev
 map -hosts       0Bi    0Bi    0Bi   100%       0          0  100%   /net
 map auto_home    0Bi    0Bi    0Bi   100%       0          0  100%   /home
 /dev/disk2s4    15Gi  2.6Gi   12Gi    18%       0          0  100%   /Volumes/gree2

fixed

 $ sudo diskutil unmount /Volumes/GREE2
 Volume GREE2 on disk2s4 unmounted

 $ df -h
 Filesystem      Size   Used  Avail Capacity iused      ifree %iused  Mounted on
 /dev/disk1     233Gi  165Gi   67Gi    72% 2422777 4292544502    0%   /
 devfs          187Ki  187Ki    0Bi   100%     646          0  100%   /dev
 map -hosts       0Bi    0Bi    0Bi   100%       0          0  100%   /net
 map auto_home    0Bi    0Bi    0Bi   100%       0          0  100%   /home

 $ sudo dd if=CentOS-6.5-x86_64-bin-DVD1.iso of=/dev/disk2s4