When running certain applications inside a docker container, such as deluge, I get “Function not implemented:” errors. The /var directory is mounted on a ZFS volume, other than that I do nothing special. If I use the same image on my vm running the same version of ubuntu (14.04.1) and docker (1.4.1) everything will function as expected. Is there an incompatibility with a /var partition mounted on a ZFS volume?
yes. zfs is not yet supported, and Docker uses specific features of a subset of filesystem drivers - aufs, btrfs, devicemapper and overlayfs to function.