Re: Questions about file-system snapshot - fss(4)

[Jürgen Hannken-Illjes <hannken%eis.cs.tu-bs.de@localhost>]

On May 14, 2011, at 4:40 PM, Paul Goyette wrote:

> I'm a bit confused about fss ...
> 
> The name claims that it makes a snapshot of a filesystem, but the path 
> argument to fssconfig(8) is a pathname.  The man page doesn't document any 
> requirement that the path argument refer to the mount-point of a filesystem.

The path argument must refer to the root of a file system.

> So, what happens if you specify a normal file as the path argument?  And what 
> happens if you specify a directory somewhere within (but not at the root of) 
> a filesystem?

You get an error (EINVAL).

> Second question: the man page states that fss(4) is still experimental (since 
> 2005).  Is there a known list of things that are broken?  (A search through 
> gnats doesn't find any PRs.)

There are some problems with journalling file systems (-o log) at least.  
Starting with NetBSD 6.0 it will no longer be experimental.

> Finally,
> 
> Assuming that /home is the root of a mounted filesystem, if I create a 
> snapshot using
> 
>       fssconfig -c /dev/fss0 /home /var/tmp/
> 
> can I then use
> 
>       dump -0a /home | ...

No. You could use `dump -0a /dev/rfss0' but the preferred usage is `dump -0aX 
/home', see dump(8) for details.

> to get a self-consistent backup of the /home filesystem?
> 
> 
> 
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--
Jürgen Hannken-Illjes - hannken%eis.cs.tu-bs.de@localhost - TU Braunschweig 
(Germany)