Flashing a micro SD drastically reduces the size

Flashed a 64GB micro SD, and while it works fine, the effective size has been reduced to 45MB. I need to put some video files in there too so I need to use the rest of that space.

It’s FAT32, macOS 10.13.6.

I suspect I may have done something wrong when formatting the card, or possibly need to change some options when flashing. Anyoe have any ideas? Experienced the same problem?


I am a bit new to this and I might be wrong here.

I suspect when you put the sd card back into your mac after flashing it mounts only the first partition on the card.

As shown here, balena OS has 5 partitions, the last of which is where you would want to put video files.

I think you should try some of the stuff mentioned in here to mount the last partition and then you should be fine to write your data to the card.

Good luck!

Yup @tacLog is correct here! By default macOS does not support the other filesystems used on the card so you can’t see them unless you take a look at some of the methods in the link shared.

1 Like

Hi, what image are you flashing onto the SD card? Etcher flashes that image exactly, and doesn’t affect your card’s size.

What likely happens, is that the image has partitions that are formatted with a file system which macOS cannot read natively. For example if you are flashing a balenaOS image, there the first partition is a FAT32 partition with about that much size, while, the rest are ext4 partitions, and I think you would see behaviour similar to this, if your system cannot read ext4 file system. You can try to plug the SD card into a Linux machine, or try to erase the partitions on the card currently to check (and then reflash later on), for example following these hints https://github.com/balena-io/etcher/blob/master/docs/USER-DOCUMENTATION.md#recovering-broken-drives

Let us know how it goes, and rest assured, your SD card capacity does not change by flashing it with Etcher.

Correct, macOS doesn’t support extfs. I’d add one thing - there’re free ways how to mount extfs (2, 3, 4) on the macOS, but they’re not reliable. I mean, read only is mostly fine, but read & write has some issues.

If you’re willing to pay, there’re commercial alternatives, like this one.

This post is just for demonstration of what you have experienced.

macOS only supports FAT and it’s this small blue portion. Rest is unsupported. But when you install the commercial SW I linked in the previous post, you can access everything …

… and mount / unmount it from the menu bar icon …

BTW I’m not affiliated with this vendor in any way, I’m just using this SW, because of the same problem.

Great responses, thank you everyone. I suspected it may have been a mac thing, I usually do this kind of stuff from home on my windows PC and never had a problem like this. I’ll give it a quick go on that before I really get stuck in to mac based fixes.

The image I’m flashing is ofxPiMappper:

I downloaded the latest, it has the same damn bug… 64 gb turned into a 15gb sd card.
Mac OS Mojave here.