https://wiki.smartos.org/display/DOC/Creating+a+SmartOS+Bootable+USB+Key
https://wiki.smartos.org/display/DOC/Download+SmartOS
Use ethcher or dd.
diskutil list
/dev/disk2 (external, physical):
#: TYPE NAME SIZE IDENTIFIER
0: FDisk_partition_scheme *16.0 GB disk2
1: 0x17 2.9 GB disk2s1
2: DOS_FAT_12 NO NAME 720.9 KB disk2s2
diskutil unmountDisk /dev/disk2
gunzip smartos-latest-USB.img.gz
sudo dd bs=1m if=smartos-latest-USB.img of=/dev/disk2
diskutil eject /dev/disk2