Disk formats/auto-expanding FAT images?

While there seems to be significant information about using etcher to burn existing images, i am having a hard time finding out how to create images for use in Etcher and what image formats are specifically supported.

Obviously straight bit-for-bit “dd” style images are supported as well as various compressions on top of that, but are there any other formats? Particularly ones that would allow FAT32 image to be expanded to any USB drive while filling the entire capacity of the drive during the process of writing (to create a bootable USB drive that is also readable - basic MBR partition table with bootloader and 1 FAT32 partition filling the disk )? Or am I barking up the wrong tree here?


Hey @mlasevich, disk images are generally one-to-one images of a particular disk, and while technically possible to a certain degree, I’m not aware of a format that would support what you’re thinking about.
Some reasons for that would be that not all file systems are resizable by design, and would require re-formatting & copying of all files, which would or could alter properties of files, and also would require the tool writing those images to support all file systems under the sun to do so.

Hope this helps,

It seems like a backup of a single system for restore to same exact single system is a far less common use case than things like distributing a pre-loaded image of a machine or OS for mass consumption - a situation where you would not likely to know or control exact size of a target (like when your target is a user provided USB drive or SD card…)

I mean, 20-30 years ago there were tools like Ghost, that were quite capable of making an image of a drive and then restore it to another drive, while automatically adjusting to the size of the drive, including expanding/contracting image to fit the size of the target without having to reformat. It seems odd that a modern tools seems to have lost that capability, but perhaps Etcher is not the right tool for this - you do need to go beyond the DD-like bit image and actually start understanding the data you are backing up - which I am guessing is much more involved than what Etcher is doing…