Current status of nullfs and/or unionfs?

Danny Braniss danny at
Thu May 5 23:18:55 PDT 2005

> Eirik Øverby writes:
>  > [...]
>  > What can I expect to see when trying nullfs and/or unionfs today? Has
>  > anything changed? Do I have even a remote chance of making it work - and if
>  > it doesn't work, what are my chances of anyone having time or energy to look
>  > into it? I'm an admin only, no coder, otherwise I'd be happy to look into it
>  > myself.
> I'm using unionfs to mount a copy of my ports tree into a jail on a
> fairly currently patched 5.3 system.  It works beautifully except that
> it sometimes can't be unmounted as the machine shuts down, leading to
> an fsck.
> I've been trying to characterize it.  Seems like I can mount it, start
> a jail, stop the jail, and unmount it just fine.  However if I do
> anything in the jail's ports tree, then it won't unmount.  Last
> experiment I did was to log into the jail and do a couple of 'syncs',
> then log out, shut the jail down and unmount it.  That worked that one
> time.
> Not enough to file a bug yet, but the anecdote might be useful.

we use unionfs with our diskless, mounting the read-only root via nfs, then
union /etc with a memory file system, the per host files (rc.conf, fstab ...)
get copied to it, so that after a reboot no need to fsck anything. works
like a charm!

a happy user of unionfs,

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