Issues with CM3 images

Hi !

We created our own image and use Balena Etcher for flashing. We use CM3 modules and the CM3 IO board for this. RPI Boot is installed properly.

It works on fresh/clean CM3. It does NOT always work on CM3 modules with an (other) image on it.
Mostly works on second or third time. The image does not boot. Does Balena change settings in the tables?
Used versions 1.5.50 and 1.5.59

There are other users here reporting failed images on other devices. Perhaps this is the same effect.
We know that there are side effects with the FLASH and partitions with FAT/FAT32 (Raspberry page talking about RPIBOOT at the bottom, images not booting properly). We fixed this to be always FAT32 (table and dump of one partition is now FAT32), but this is not the reason of the failure. Rufus always works with our image.

We presently use Rufus instead for this reason.

There also is a difference in speed:
Use rpiboot to detect CM3 -> speed in Rufus only 5MB/s+
Use Balena etcher to detect CM3 -> speed in Rufus >15MB/+.

I would like to stick to balena, because balena shows 21MB/s, but image does not always work.

Also Eject after Successful does not work here (WIN7 / 10 64bit), because image is not mounted at all after flashing (FAT32 partition). Rufus instead opens this partion after flashing as a readable drive.

Best regards,


Does Balena change settings in the tables?

Etcher does not modify the image you provide, it just copies it to the destination device.

It does NOT always work on CM3 modules with an (other) image on it.

How does it “NOT always work” ? Is there an error ? Does the flash complete ?

There also is a difference in speed:

Rpiboot and etcher use the same method: they send a firmware to the device that turns it into an usb mass storage device (like an usb stick).
The only difference is the firmware they send. The one sent by etcher allows faster write speeds.


  1. Etcher does not change the image, of course…
  2. No error message. Even no verify error. The CM3 does not boot.
  3. The speed of Etcher is very fast, this is great.

I expected to see the image mounted after flashing, because EJECT is disabled. This does not work with good CM3.

Are you sure your image is bootable?
Maybe it works in rufus because rufus makes it bootable?


Yes, it is bootable. It is created as a bootable image.

Tested with dd (Linux) and other windows tools (Win32DiskImager).

It nearly always works with Etcher on new CM3 out of the box. But it fails with CM3 where data is present or other partitions are present. Rufus seems to delete partitions first as one can see in the status line. Perhaps this makes the difference? That would be like you call it making it bootable by default.

Could you please share the disk image?

No. This is not possible…
Perhaps I can share parts of it (partition tables or other required information).


Thanks, sharing as much detail as possible for the partition here would be useful. Unfortunately without an image artefact, it becomes very difficult for us to determine why your custom image doesn’t work.

Best regards,


Do you need a specific memory area (dump)?


A dump of the partition map (say using fdisk would be useful) as well as as much other detail and information you can share, please.

Best regards,


We would need a disk image that can reproduces this behaviour.

What do you mean by “But it fails with CM3 where data is present or other partitions are present.” ?
Do the write and verification succeed?
If yes, does it make the compute module boot?
If yes, can you describe what you see on the screen?

If no, is the first partition on the disk bootable? (check with fdisk).
What are the differences between a bootable CM3 and a non bootable CM3 no the disk?