diskutil

  Utility to manage local disks and volumes.

  - List all currently available disks, partitions and mounted volumes:
    diskutil list

  - Repair the file system data structures of a volume:
    diskutil repairVolume /dev/diskX

  - Unmount a volume:
    diskutil unmountDisk /dev/diskX

  - Eject a CD/DVD (unmount first):
    diskutil eject /dev/disk1