How to write a raw.xz image into a drive without wiping it?

Hello. I’m trying to install Fedora into a SSD for my Raspberry Pi 4.

Right now the SSD is empty, but at some point it’ll have to be full of my data, that I don’t want to lose, so I’ll put it in a separate partition.

However, every time I use arm-image-installer, it tells me it will wipe the disk completely, so I’m worried about how will I be able to install a different OS with the same data disk in the future. Is there a way to override only some partitions and not others? Or a way to use anaconda somehow to set it up just like usually, so I can choose where to install stuff?

I assume you are using the fedora workstation image for arm. If so then that is normal. Once the image is installed and you boot fedora on the device then the partition can be resized to allow access to the full available space or to the size you choose.
It does the same for me when I install the image to a 64 GB sd card, but expanding the partition works for access to the full device.

Be aware that the Pi boots differently than a PC and I am not sure you can install more than one OS on the boot device. I don’t think grub is installed the same, and definitely not with uefi. It may be simpler for you to install to an sd card and use the SSD for data. That way a simple switch of the sd cards gives a different OS without affecting the SSD.

I guess I’ll do that. I was hoping to be able to just use the ssd, but if that means not being able to switch os later, then I’ll have to use the SD for it.