root@enderman:~# df -h
Filesystem                            Size  Used Avail Use% Mounted on
udev                                  7.8G     0  7.8G   0% /dev
tmpfs                                 1.6G   22M  1.6G   2% /run
/dev/sda2                              40G   25G   15G  64% /
tmpfs                                 7.8G  712K  7.8G   1% /dev/shm
tmpfs                                 5.0M  4.0K  5.0M   1% /run/lock
tmpfs                                 7.8G     0  7.8G   0% /sys/fs/cgroup
/dev/sda1                             510M   30M  481M   6% /boot/efi
/dev/sda5                              97G   59G   38G  62% /home
cgmfs                                 100K     0  100K   0% /run/cgmanager/fs
slime.local:/mnt/zfs-pool/james-data  1.8T  1.6T  233G  88% /home/james/more-data
tmpfs                                 1.6G     0  1.6G   0% /run/user/115
tmpfs                                 1.6G   12K  1.6G   1% /run/user/1000
root@enderman:~# btrfs filesystem df /
Data, single: total=38.49GiB, used=24.13GiB
System, single: total=4.00MiB, used=16.00KiB
Metadata, single: total=1.01GiB, used=624.06MiB
GlobalReserve, single: total=224.00MiB, used=0.00B
root@enderman:~# touch test
touch: cannot touch ‘test’: No space left on device
root@enderman:~# btrfs subvolume list -a /
ID 257 gen 202615 top level 5 path <FS_TREE>/@
ID 264 gen 25 top level 257 path @/var/lib/machines
ID 301 gen 180487 top level 5 path <FS_TREE>/@apt-snapshot-release-upgrade-wily-2015-10-26_17:25:11