I was using the dd command to burn a .img file to a micro SD card which was connected to my mac through a usb SD card adaptor. I need to unmount(not eject) the device first before I could use dd to burn the image file. I did that with the umount command. After the burning was done, I unplugged the SD card adaptor when it prompted me that the device was not ejected properly.
I was worried that I was doing it wrong. I tried to eject the device but couldn't find any icon in finder after the unmount. How should eject a unmounted device correctly?