So if you follow up with Docker, you might have found out that the default storage that is provided with a normal Docker installation, is backed by the mighty aufs, created by the awesome Junjiro Okajima.
But out there there is another file system that is faster, with smaller footprint, etc. It's named OverlayFS, and was merged in the main kernel. Sounds to good to be true? Well read about it.
TL;DR Docker With OverlayFS on Ubuntu 14.04:
Now, this file system is available only from kernel version 3.18 and up. If you just installed Ubuntu 14.04, as of this date (10th of November, 2015), you should have 3.19 already installed. If you have an older existing Ubuntu 14.04 you need to update your kernel manually.
So let's see the current version of the kernel:
In my case looks good (I actually already updated).
If the kernel version is NOT 3.19, you need to update, but don't worry it's super easy:
Install the new kernel (if not already on 3.19)
Thanks to the Ubuntu LTS Hardware Enablement Stack, the newer kernel is available (and supported) for install.
Afterwards reboot, and check if you got the new Kernel:
Now, if I would be you, I would do that on a new Docker instance. If you already have docker installed, I assume you removed it, and deleted the data (option b. is you export your images, and reimport them):
Remove Old Docker (optional)
Use OverlayFS instead of aufs
Now after the install docker will be already running, but using the aufs storage:
So let's change that:
Then let's check it now:
Done! Great Job.