Previously in order to run Linux containers on a Mac, you needed to install VirtualBox and have an embedded Linux virtual machine that would run the Docker containers from the Mac CLI. There would be a network endpoint on your Mac that pointed at the Linux VM, and the two worlds are quite separate.
Docker for Mac is a native MacOS X application that embeds a hypervisor (based on xhyve), a Linux distribution and filesystem and network sharing that is much more Mac native. You just drag-and-drop the Mac application to /Applications, run it, and the Docker CLI just works. The filesystem sharing maps OSX volumes seamlessly into the Linux container and remaps MacOS X UIDs into Linux ones (no more permissions problems), and the networking publishes ports to either `docker.local` or `localhost` depending on the configuration.
A lot of this only became possible in recent versions of OSX thanks to the Hypervisor.framework that has been bundled, and the hard work of mist64 who released xhyve (in turn based on bhyve in FreeBSD) that uses it. Most of the processes do not need root access and run as the user. We've also used some unikernel libaries from MirageOS to provide the filesystem and networking "semantic translation" layers between OSX and Linux. Inside the application is also the latest greatest Docker engine, and autoupdates to make it easy to keep uptodate.
Although the app only runs Linux containers at present, the Docker engine is gaining support for non-Linux containers, so expect to see updates in this space. This first beta release aims to make the use of Linux containers as happy as possible on Windows and MacOS X, so please reports any bugs or feedback to us so we can sort that out first though :)
The bug above has been reported to Apple and they've reportedly fixed it in the latest 10.11.4 seeds, but we've put in a workaround that detects ACPI sleep events and freezes vCPUs just before going into hibernate mode. None of the beta testers have reported any sleep crashes using Docker for Mac recently, so if you do see anything of this nature please let us know.
Perfect. We had to ditch Kitematic on OS X due to the lack of port forwarding, since we couldn't get OAuth redirects to work when developing locally.