[Pkg-zfsonlinux-devel] Summary of ZFS on Linux for Debian

[Turbo Fredriksson]

On Jun 12, 2015, at 7:00 PM, Aron Xu wrote:

> After the upload, we tried to talk with Debian installer team on how
> to maintain an out-of-tree kernel module for the installer but
> unfortunately it's not feasible at the moment.

Just want to chip in with my two cent here and clarify parts of this.


What this actually means is that getting ZoL into Debian GNU/Linux
won't be much of a problem. We just need to wait for the bureaucracy
to do it's work. We might have to modify the packages we already have
in smaller ways to fully adhere to the Debian GNU/Linux packaging
policies etc, but we'll get it in "eventually". Hopefully "soon".


The problem is the "out-of-tree modules" part. This means, outside of
the Linux kernel source tree. Because of the CDDL license, we'll NEVER
going to be able to include it in the kernel (unless someone spends
_a lot_ of time to do a clean-room reimplementation of ZFS in GPL).

This means that getting ZoL in the installer images of Debian GNU/Linux
will be almost impossible. ZoL is available in two parts - the user
land (the zfs and zpool commands for example) and the kernel modules.

These are usually built on the host from dkms packages (which is the
ZoL source code and special rules to be able to build it safely and
easy). These require a complete build environment (compiler, linker,
kernel headers or the full kernel source etc etc).

The installer is simply not big enough for a complete build environment,
which is why we won't be able to provide ZFS as an install option.

The Debian GNU/Linux installer team feel that having out-of-tree modules
is to much of a hassle and can/will lead to maintenance problems - keeping
this in sync.

Technically, I somewhat agree with them, but the feeling from the
pkg-zfsonlinux team is that we might be able to do that. The keyword
here is unfortunately "might"… We're all very busy people, and if we're
out of touch for a short time, their worries will be fulfilled.


Now, ALL is not lost. I have done some experimentation with using
zfs-fuse in the installer to create and mount the filesystem(s), and
then use ZoL and the dkms process in the resulting install.

Tests have shown that this is very possible, but it will need more
work and quite a lot of more testing to be fully stable and something
that we, as a distribution, can offer to our users.


We could also ignore all this and not offer ZFS as an install option,
and require users to install on some other filesystem, and then install
ZFS once the system reboots into the new install.

This is very likely to be the first step, once ZoL have been fully
accepted into the FTP archives.


A third, highly theoretical solution, might be to offer downloadable
kernel modules outside the Debian GNU/Linux distribution, much like
many graphical drivers etc (adobe reader is one such I think) is
provided.
-- 
Turbo Fredriksson
turbo at bayour.com