Jail FS questions.
Marc G. Fournier
scrappy at hub.org
Thu Oct 9 18:56:40 PDT 2003
On Thu, 9 Oct 2003, Kris Kennaway wrote:
> On Thu, Oct 09, 2003 at 05:00:02PM -0400, Kenny Freeman wrote:
> > > I've been reading about unionfs and nullfs (well, more skim reading
> > > really; I'm not FS guru, which is why I'm asking here) and one of these
> > > sounds like it could be the idea solution. At first glance I'd say that
> > > unionfs would be the way to go.
> Both unionfs and nullfs are documented to be broken. Seriously, those
> big scary warnings in the manpages are there for a reason!
> Having said that, some people have reported success in certain limited
> situations. If you insist on using them, then you're on your own
> if/when it breaks.
> This means: do not complain to us when your system crashes and you
> lose a filesystem.
Wow, what a way to encourage ppl to report bugs ... glad there are ppl
like Tor and David Schultz out there that are interested in fixing bugs
and not ignoring them ...
You know, its this attitude that would have kept Christopher Columbus in
Europe ... all the "big scary warnings" said that the world was flat back
As everyone on -STABLE knows by now, I very heavily use unionfs on very
heavily loaded systems ... between Tor Egge and David Schultz, all of the
unionfs related crashes I've experienced have happily disappered ... my
unionfs related server hangs (dealing with vnodes) have also disappeared
... I have two things left that I know will trigger a crash: run
pkg_delete on a unionfs'd jail, and it gives the unionfs_dir crash, and
create a socket on a uniofs directory, and it causes a crash ... so I'm
careful not to create sockets (/var isn't a unionfs mount as a result) and
I rm'd pkg_delete so that it couldn't be accidentally run ...
I have yet to "lose a file system" except when a hard drive went bad ...
my biggest 'headache' right now is that periodically, if the server does
crash, fsck takes a very very long time due to 'ZERO LENGTH DIRECTORIES'
So, based on almost two years of heavy experience with unionfs ... yes,
there are some problems with it, and yes, there used to be some that
warranted the "big scary warning", but that state of unionfs today, IMHO,
the warning now is way overstated, and is only serving to give an excuse
for those wishing to ignore problem reports based on it ...
In fact, if you ever followed some of the threads discussing what it would
take to fix unionfs, you would see several developers mentioning that the
whole VFS layer code needs a complete re-write ... several have suggested
completely removing some of the more 'damaged aspects' (ie. nullfs and
unionfs) to reduce the time required to do the re-write, and re-adding
them in at a later date ...
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