I had to revert from compressed BTRFS to Ext4 on my tiny netbook partition, as it wasn't playing nice. That's a pity, as Ubuntu is highly compressible and compression didn't slow it down. The system occupied less than half of the space and reported such, however when I was starting to fill up the space, it complained of insufficient space. Probably because of metadata allocation. As I didn't want to reinstall the system, I went the more costly route: * I've rebuilt the partition in an image on ext4, * copied over the data * copied the initrd image from another computer of mine with the exact same system, both were updated at the same time - otherwise it couldn't read the new kind of partition * adjusted grub settings * reinstalled grub (was extra painful when I attempted to do that inside an image..).