Writing image to SD card
These are the steps to write an raspberry pi OS image to an SD card on MacOS
1. Insert card on reader
Identify the disk number
diskutil list
2. Unmount the disk
unmountDisk /dev/disk2
3. Write the image
sudo dd bs=1m if=hassos_rpi3-2.12.img of=/dev/rdisk2 conv=sync
4. Eject card
sudo diskutil eject /dev/rdisk2
Done!
https://www.raspberrypi.org/documentation/installation/installing-images/mac.md