astralbijectioncurl > /dev/sda: How I made a Linux distro that runs wget | dd
Reminded me of how to install Alpine linux (which isn't available) on Oracle cloud over an ubuntu install. It uses dd and has the advantage of having a console.
I had found it in a github gist when I used it but here's a similar blog post.
Wait hold on, can you not simply just access the underlying volume/block device using an API? The VMs in OCI have a boot volume that is attached, so I reckon it's possible to "mount" this somehow and overwrite it with whatever data you want.