Re: ZFS rollback snapshot general question

On Fri, Jun 26, 2026 at 10:14:17AM -0400, Bobb Shires wrote:
> Hi Kevin... Yes, I knew I had done something incorrectly.
> Thanks for the reminder.

I meant it as an explanation of why it went south on you, that's all.

ZFS has too many footguns.

> On Thu, Jun 25, 2026, at 21:11, Kevin P. Neal wrote:
> > Really, the rollback should have been blocked and not allowed.

Seriously, this particular case really should have been stopped by the
kernel. And why did it give you a script/command without a warning that
it shouldn't be used on a running system? That's not very friendly.

The cases that always get me are the ones where I accidentally mount a
filesystem over top of another one, typically the root filesystem. That's
a bad day when I have to drive out to the datacenter because my server
can't reboot with / overlaid by some other dataset like, for example, a
root filesystem for a newer version of FreeBSD. Wow do I hate that.

And I hate that I keep finding more ways to make the same mistake. For
example, a "zfs send | zfs receive" of /usr/local to a new boot environment
will mount the new /usr/local over top of the already mounted /usr/local
and ruin my ongoing poudriere builds. Well, unless I remember to use the
"-u" option on the receiving end. Which I didn't remember on my upgrade
to 15.1.  *sigh*

I have used zfs rollback before, but never in a case where the kernel
should have stopped me. You got unlucky. Myself, I find other ways to get
unlucky instead.

I like ZFS, but man is it easy to get into trouble with it.
-- 
Kevin P. Neal                          from "Crito" by Plato, 360 BCE:
"But why, my dear Crito, should we care about the opinion of the many?
Good men, and they are the persons who are worth considering, will
think of these things truly as they happened." - Socrates