MBP-di-Giuseppe:~ giuseppe$ diskutil eraseVolume jhfs+ CLE disk4s3
Started erase on disk4s3 Install OS X Yosemite
Unmounting disk
Erasing
Initialized /dev/rdisk4s3 as a 9 GB case-insensitive HFS Plus volume with a 8192k journal
Mounting disk
Finished erase on disk4s3 CLE
MBP-di-Giuseppe:~ giuseppe$