I had a similar situation happen with running multiple virtual machines where their storage was a .vdi file - the files grew too big and maxed out my storage. O

I had a similar situation happen with running multiple virtual machines where their storage was a .vdi file - the files grew too big and maxed out my storage. On next boot ubuntu would not start, same error telling me disk is too full. I had a recent backup so i just reinstalled everything. I always make sure there is some space on the disks from that moment on.