What is /dev/zfs?

[Alan Somers]

On Thu, Jun 29, 2017 at 8:28 AM, Patrick M. Hausen <hausen at punkt.de> wrote:
> Hi, folks
>
> any pointer to an explanation would be nice,
> there seems to be no zfs(4) manpage ...
>
> Reason for asking: I have a piece of software
> that uses 14,000 ioctl() calls on that device during
> one execution and I'm asking myself what it tries
> to do.
>
> Thanks!
> Patrick

The zpool and zfs commands do everything through ioctls, and /dev/zfs
is the device node those ioctls are bound to.  You can't read from it
or write to it; all you can with /dev/zfs is use ZFS's custom ioctls.

-Alan