Date: Wed, 1 Jun 2016 12:04:44 -0400 From: Jeff Terrell <jeff@altometrics.com> To: freebsd-virtualization@freebsd.org Subject: Re: Running FreeBSD docker images on non-FreeBSD hosts Message-ID: <CA%2BMCM4s%2BEFcbNV=TaV1Ca_gwFONgDnGEm8p%2BD5eUGC2trX=_-A@mail.gmail.com> In-Reply-To: <d1475a4a-97f9-ae4e-7ddb-4716e3f58427@pix.net> References: <CA%2BMCM4v308E8iOzP9TCo57PO2ZqriD%2BevYh9nt6XWvLP%2BWmAUA@mail.gmail.com> <d1475a4a-97f9-ae4e-7ddb-4716e3f58427@pix.net>
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On Tue, May 31, 2016 at 6:08 PM, Kurt Lidl <lidl@pix.net> wrote: > What isn't really explained in so many words -- the container uses the > system calls from the hosting computer to evaluate anything that it > needs the "kernel" to do. So your "FreeBSD docker" image, when run on > a Linux machine, is attempting to make FreeBSD system calls into the > Linux kernel. > > You'd have to use some other solution to provide a "FreeBSD system call interface" to your FreeBSD docker image. > > The recent import of Linux 64bit emulation in FreeBSD allows for running > stock "docker" images on FreeBSD, because there's now a shim that > translates Linux system calls to FreeBSD ones. > > On the Mac, they have shims that provide filesystem access to the Mac's filesystems, and a virtualized machine using the xhyve stuff, providing > the Linux system call interface. > > Make no mistake about, docker is Linux inside. > > If you want to run FreeBSD inside a virtual machine, try the xhyve stuff > on the Mac, or under KVM on Linux. > > -Kurt Ah, now I get it. I didn't realize that system calls were the interface between the docker images in a container and the host. But that definitely explains why the FreeBSD images won't work apart from a FreeBSD host. So it looks like, if I'm committed to docker, I could run FreeBSD inside a KVM inside a container on Linux. Then others who might be interested in FreeBSD could play around with it on their Linux hosts via docker. And I suppose, since I need to mount a volume, I'd need to mount it both into the docker container and, from there, through KVM to FreeBSD. Not fun, but plausible at least. Thanks very much for the explanation, Kurt! -- Jeff Terrell, Ph.D. | Chief Technology Officer ALTOMETRICS, Inc. (919) 357-3116 | www.altometrics.com
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