Current status of nullfs and/or unionfs?

EirikØverby ltning at
Fri May 6 00:20:10 PDT 2005

On 06-05-05 08:18, "Danny Braniss" <danny at> wrote:

>> 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!

Interesting approach. Is this with 4.x or 5.x? How do you union-mount /etc
(mount command/fstab entry)?


> a happy user of unionfs,
> danny

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