I struggled for a bit to get ethOS to boot from USB. based on the installation instructions from http://ethosdistro.com/kb/#writing-osx

the command provided in the guide is

sudo dd if=/Users/YOURUSERNAME/Desktop/ethos-*.iso of=/dev/rIDENTIFIER bs=1m (note the r)

sudo dd if=/Users/alinawab/Mining/ethos-1.2.7.iso of=/dev/rdisk3 bs=1m

the issue is that in the drive identifier in mac disk utility is in the format disk1s1 where s1 is the partition. the command needs to be run without the partition information, so disk3s3 should be only disk3

learningcurve in building a miner. more posts to come