Make a disk image formatted with both ext2 and FAT at once

cursedfs

Make a disk image formatted with both ext2 and FAT, at once.

~/cursedfs% wget 'https://github.com/NieDzejkob/cursedfs/releases/download/v1.0/cursed.img'
~/cursedfs% sudo mount -o loop -t ext2 cursed.img mountpoint/
~/cursedfs% ls mountpoint/
mkfs.cursed
~/cursedfs% sudo umount mountpoint/
~/cursedfs% sudo mount -o loop -t msdos cursed.img mountpoint/
~/cursedfs% ls mountpoint/
gudnuse.ogg

Why?

I got nerd-sniped

How?

It turns out this is surprisingly simple to do: just create a FAT volume with a lot of reserved sectors and put the ext2 into the reserved sectors. This works because the filesystems choose different places to put their superblock: FAT uses the very first sector, while ext2 leaves the first kilobyte unused.