svn commit: r274653 - head/usr.sbin/freebsd-update

[Mark Felder]

On Tue, Nov 18, 2014, at 08:24, Konstantin Belousov wrote:
> Why do you suppose that md-backed volumes are not persistent ?
> vnode-backed devices are stable.
>

You're right, a vnode-backed filesystem would definitely be persistent.
Clearly I've done a poor job of researching this thoroughly. I've now
read md(4) in its entirety and remember mounting disk images like
Linux's "mount -o loop" in the past. I don't see a way to reliably
detect an mfs filesystem because it uses md and masquerades as ufs in
df's output. Do you have any suggestions on how to detect this reliably?

On the other hand, anyone could write a filesystem we aren't
blacklisting and fall into the same trap. I thought this was going to
help a few people since Oliver reported it and seemed to have a valid
use-case for a tmpfs mounted /var but still wanted to use
freebsd-update. Instead I'm beginning to think we should just throw this
away and add an entry into BUGS in the man page and call it a day. We
can't keep everyone from shooting their feet off and we probably
shouldn't waste our time trying.


Thoughts?