Create bootable USB on OSX

– Identify the disk number for the USB disk inserted, usually you can find it from the “Name” and “Size” field.
Below eg: , We inserted a USB with 4.1 GB size (so as the identified: “disk2”.)
Open terminal and execute the following commands:

sh-3.2$ diskutil list
/dev/disk0
#: TYPE NAME SIZE IDENTIFIER
0: GUID_partition_scheme *120.0 GB disk0
1: EFI EFI 209.7 MB disk0s1
2: Apple_CoreStorage 119.0 GB disk0s2
3: Apple_Boot Recovery HD 650.0 MB disk0s3
/dev/disk1
#: TYPE NAME SIZE IDENTIFIER
0: Apple_HFS Macintosh HD *118.7 GB disk2
/dev/disk2
#: TYPE NAME SIZE IDENTIFIER
0: UNTITLED *4.1 GB disk2

– Unmount the disk
sh-3.2$ diskutil unmountDisk /dev/disk3
Unmount of all volumes on disk3 was successful

– write the ISO file to USB using dd command
sh-3.2$ sudo dd if=Downloads/ubuntu-12.04.3-desktop-i386.iso of=/dev/disk2 bs=1m
Password:
707+0 records in
707+0 records out
741343232 bytes transferred in 139.059398 secs (5331126 bytes/sec)

– Unmount the disk
sh-3.2$ diskutil eject /dev/disk3
Disk /dev/disk3 ejected