Flashing SD Card on macOS

[RandyR]

A couple of people have mentioned that they were having issues flashing my images when using macOS, specifically when using my recommended tool, Balena Etcher. Since I had some time to 'hack', and an older Intel based PC, I decided to see what the problem might be. After doing some extensive testing on macOS (Monterey and Tahoe) I have some suggestions for users who are also having issues flashing (custom) images on macOS.

First, when decompressing .7z archives, don't rely on the default 'Archive Utility' program. I have compared the sha256 hash of the original .img file with the one extracted from the downloaded .7z archive file and they are different (I saw this on both macOS versions). I suggest using 'The Unarchiver', which correctly extracts .7z files.

On macOS 12 (Monterey) I was unable to flash successfully using Balena Etcher v2.1.4. When the SD card was used in a Pi5 the OS froze. I was successful using Raspberry Pi Imager v2.0.7 (select custom image if flashing one of my pre-made images).

When using macOS 26 (Tahoe) with Balena Etcher v2.1.6, I had no issues flashing and using the SD card in my Pi5. With Raspberry Pi Imager v2.0.8, I was also successful when flashing a properly extracted .img file (using The Unarchiver).

Another option that is available, but somewhat riskier is to use commands in the macOS terminal. This worked on both versions of macOS that I tested. Here is the procedure:

Flashing SD Card using dd on macOS

1. insert USB card reader containing micro SD Card into PC
2. Open a Terminal window and enter the command:

diskutil list

• find SD card device name (/dev/disk#) in list using size of card, e.g. a 32GB SD card with an old version of PicoChess might look like this:

/dev/disk2 (external, physical):

   #: TYPE NAME SIZE IDENTIFIER

   0: FDisk_partition_scheme *31.3 GB disk2

   1: Windows_FAT_32 ⁨bootfs⁩ 536.9 MB disk2s1

   2: Linux 30.7 GB disk2s2

• Unmount any mounted partitions on the SD card:

diskutil unmountDisk /dev/disk2

• Navigate to the folder containing the .img file

cd <folder/with/image>

• Use dd to flash the image (use rdisk# instead of disk# to flash raw image - faster).
• NOTE: make sure you use the correct disk number!!!

sudo dd if=PicoV4Desktop64-bit.img of=/dev/rdisk2 bs=1m

• Eject the SD card and transfer to Pi:

diskutil eject /dev/disk2

I hope this helps anyone having difficulties flashing SD cards using macOS..

Randy

[Dirk]

Thanks Randy!