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
#:                       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
#:                       TYPE NAME                    SIZE       IDENTIFIER
0:                  Apple_HFS Macintosh HD           *118.7 GB   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
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