Sudo dd if=/dev/rdisk2 of=_asiar-backup.img bs=4m Knowing this it is easy to backup the SD card. So in my case the SD card was assigned to /dev/disk2 and therefore the raw device is /dev/rdisk2. The raw device corresponding to an OS device has exactly the same name prepended with an r. However, MacOS also knows about raw devices and using dd with the raw device is MUCH faster. The first layer we just saw when we checked what OS device was assigned to the SD card. for MacOS and SD cards a sensible block size is 4 megabytes which is specified as 4m. The block size specifies how many bytes get read from source and written to target at the same time. If you want to restore the SD card then source is the file and target the SD card device. If you want to back up the SD card then source is the SD card device and target a file.

Source is where you want to copy the data from and target where to. The dd command requires root privileges and the general command structure is Issuing the mount command again, you can see that the partition was unmounted. dev/disk2s1 on /Volumes/BOOT (msdos, local, nodev, nosuid, noowners) When the SD card gets connected to the Mac, the BOOT partition gets mounted automatically and this needs to be unmounted for dd to work properly. In my case it shows that the SD card is the /dev/disk2 device. Proceed with caution and make sure to follow all steps and replace any device in the command examples with the ones used on your Mac!!!įirst thing to do is to see what OS device the BOOT partition is on.

Failing to do so may overwrite the contents of a disk unintentionally and it will be impossible to revert. Do not copy and paste and command and execute them without making sure that your Mac is using the same device names. But before you do so, I need to write this:ĭISCLAIMER These instructions contain examples of device names that are specific to my situation. The instructions for Raspbian or Ubuntu may be slightly different, especially the mounted partition names on MacOS, but if you follow the guidelines you should get it to work.įor dd, follow these following steps. This I wrote earlier today on the ZWO forum for cloning ASIAir SD cards.

Mac cloning software