On ZFS in Debian
I’m currently over at FOSDEM, and have been asked by a couple of people about the state of ZFS and Debian. So, I thought I’d give a quick post to explain what Debian’s current plan is (which has come together with a lot of discussion with the FTP Masters and others around what we should do).
TLDR: It’s going in contrib, as a source only dkms module.
Debian has always prided itself in providing the unequivocally correct solution to our users and downstream distributions. This also includes licenses – we make sure that Debian will contain 100% free software. This means that if you install Debian, you are guaranteed freedoms offered under the DFSG and our social contract.
Now, this is where ZFS on Linux gets tricky. ZFS is licensed under the CDDL, and the Linux kernel under the GPLv2-only. The project views that both of these are free software licenses, but they’re incompatible with each other. This incompatibility means that there is risk to producing a combined work with Linux and a CDDL module. (Note: there is arguments about if a kernel module, once loaded, is a combined work with the kernel. I’m not touching that with a barge pole, as I Am Not A Lawyer.)
Now, does this mean that Debian would get sued by distributing ZFS natively compiled into the kernel? Well, maybe, but I think it’s a bit unlikely. This doesn’t mean it’s the right choice for Debian to take as a project though! It brings us back to our promise to our users, and our commercial and non-commercial downstream distributions. If a commercial downstream distribution took the next release of stable, and used our binaries, they may well get sued if they have enough money to make it worthwhile. Additionally, Debian has always taken its commitment to upstream licenses very seriously. If there’s a doubt, it doesn’t go in official Debian.
It should be noted that ZFS is something that is important to a lot of Debian users, who all want to be able to use ZFS in a manner that makes it easier for them to install. Thus, the position that we’ve arrived at is that we can ship ZFS as a source only, DKMS module. This means it will be built on the target machines, and we’re not distributing binaries. There’s also a warning in the README.Debian file explaining that care should be taken if you do things with the resultant binary – as we can’t promise it complies with the licenses.
Finally, I should point out that this isn’t my decision in the end. The contents of the archive is a decision for the FTP-Masters, as it’s delegated. However, what I have been able to do is coordinate many conflicting views, and I hope that ZFS will be accepted into the archive soon!