add note to docs about overlay + btrfs
Docker-DCO-1.1-Signed-off-by: Jessica Frazelle (github: jfrazelle)
@@ -181,6 +181,9 @@ share executable memory between devices. Use `docker -d -s btrfs -g /mnt/btrfs_p
The `overlay` is a very fast union filesystem. It is now merged in the main
Linux kernel as of [3.18.0](https://lkml.org/lkml/2014/10/26/137).
Call `docker -d -s overlay` to use it.
+> **Note:**
+> It is currently unsupported on `btrfs` or any Copy on Write filesystem
+> and should only be used over `ext4` partitions.
#### Storage driver options
