cat /etc/default/grub:
GRUB_CMDLINE_LINUX_DEFAULT="cgroup_enable=memory swapaccount=1"
GRUB_CMDLINE_LINUX="cgroup_enable=memory swapaccount=1"

root@sirius:~# docker info
Containers: 0
Images: 0
Storage Driver: btrfs
Execution Driver: native-0.2
Kernel Version: 3.13.0-48-generic
Operating System: Ubuntu 14.04.2 LTS
CPUs: 8
Total Memory: 31.33 GiB
Name: sirius.servermeta.net
ID: XXXX:XXXX:XXXX:XXXX:XXXX
WARNING: No swap limit support