If you’d like to experiment with different block sizes, just type ctrl + c to cancel the command, then you can run it again. You should see some progress feedback telling you the transfer speed. Tip: you can experiment with different numbers for the block size by replacing bs=16M with larger or smaller numbers to see if it makes a difference to the speed. Sudo gdd if=/dev/rdisk4 of=sd_backup.dmg status=progress bs=16M

Now you should run the following command, replacing 4 with whatever number you identified as your sd card: For an operation like this, it is much more efficient. The r means when we’re copying, it will use the “raw” disk. You should add an r in front of disk4 so it looks like this /dev/ rdisk4. You can run diskutil list and should see an output like below: /dev/disk1 (synthesized):Ġ: APFS Container Scheme - +500.0 GB disk1ġ: APFS Volume Macintosh HD - Data 396.0 GB disk1s1ĥ: APFS Volume Macintosh HD 11.0 GB disk1s5įrom that output we can see that our SD card must be /dev/disk4 as our card is 32GB in size and has a fat32 and linux partition (standard for most raspberry pi images). You’ll need to find out which disk your SD card represents. Do so by running brew install coreutils in your terminal. After you’ve installed homebrew, you’ll need to install a package called core-utils.You can visit this link to find out how to download and install homebrew if you haven’t already got it. Make sure you’ve got homebrew installed.basic knowledge of command line operations.macOS running a recent version (this guide was tested on macOS Catalina).If you type any of the parameters incorrectly you may accidently erase or overwrite important data. WARNING: Be very careful when running any command with sudo dd in it. This simple command line trick will have you copying or cloning a full disk image of your SD card in record time! Unfortunately this has issues reading linux partitions (well in my experience) and is often slow.

Your first thought is to probably use the built in “Disk Utility”. If you have a raspberry pi or other single board computer and would like to make a backup of it, or even clone it to another SD card, then it can take a long time.

Os x sd card writer