Example for create USB bootable for pfSense using device /dev/disk3

Make a USB bootable for pfSense on OSX

# diskutil list

/dev/disk0 (internal, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *121.3 GB   disk0
   1:                        EFI EFI                     209.7 MB   disk0s1
   2:          Apple_CoreStorage Macintosh HD            121.0 GB   disk0s2
   3:                 Apple_Boot Boot OS X               134.2 MB   disk0s3
/dev/disk1 (internal, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *1.0 TB     disk1
   1:                        EFI EFI                     209.7 MB   disk1s1
   2:          Apple_CoreStorage Macintosh HD            999.3 GB   disk1s2
   3:                 Apple_Boot Recovery HD             650.0 MB   disk1s3
/dev/disk2 (internal, virtual):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:                  Apple_HFS Macintosh HD           +1.1 TB     disk2
                                 Logical Volume on disk0s2, disk1s2
                                 808171D1-4E56-424A-963F-1E2CAE37F355
                                 Unencrypted Fusion Drive
/dev/disk3 (external, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:     FDisk_partition_scheme                        *7.8 GB     disk3
   1:               Linux                                7.8 GB     disk3s1
   

# diskutil unmountDisk /dev/disk3

# sudo dd if=/Users/Gerardo/Downloads/pfSense-CE-memstick-2.3-RELEASE-amd64.img of=/dev/disk3
1339600+0 records in
1339600+0 records out
685875200 bytes transferred in 754.134009 secs (909487 bytes/sec)