mac dd command write image to disk error bs=1m mac

// list all devices that are mounted and locate the disk your righting to. NOTE IT
$ diskutil list 

// substitute N for disk number ie disk4

$ diskutil unmountDisk /dev/diskN 

// copy the image or write it. the following copys. notice the 'r' added in front of disk
// this speeds up the process. press ctrl T to check progress after it starts

$ sudo dd bs=1m if=path_of_your_image.img of=/dev/rdiskN; sync

If the command reports dd: /dev/rdiskN: Resource busy, you need to unmount the volume first sudo diskutil unmountDisk /dev/diskN.

If the command reports dd: bs: illegal numeric value, change the block size bs=1m to bs=1M.

If the command reports dd: /dev/rdiskN: Operation not permitted, go to System Preferences -> Security & Privacy -> Privacy -> Files and Folders -> Give Removable Volumes access to Terminal.

If the command reports dd: /dev/rdiskN: Permission denied, the partition table of the SD card is being protected against being overwritten by Mac OS. Erase the SD card's partition table using this command:

$ sudo diskutil partitionDisk /dev/diskN 1 MBR "Free Space" "%noformat%" 100%

Above command will also set the permissions on the device to allow writing. Now issue the dd command again.

After the dd command finishes, eject the card:

$ sudo diskutil eject /dev/rdiskN