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Re: dump won't dump an fss snapshot on netbsd-5

On Mon, Jul 27, 2009 at 05:28:34PM -0400, Louis Guillaume wrote:
> Hi Juergen,
> Juergen Hannken-Illjes wrote:
> >On Sun, Jul 26, 2009 at 10:13:09PM -0400, Louis Guillaume wrote:
> >>I just updated the machine connected to my tape drive from netbsd-4 
> >>(stable) to netbsd-5 (stable). Now dump will not back up my fss 
> >>snapshots...
> >
> >The /dev/fss? devices will not allow multiple opens.  To dump a snapshot
> >please use the -x / -X flags.  In your example it would be:
> >
> >    dump -L maat-home -b 32 -0eautf /dev/nrst0 -x /var/tmp/maat-home /home
> >
> This appears to work properly, however I have no indication that a 
> snapshot was made or even used aside from this:
>   [16:42:52 EDT] DUMP: Dumping a snapshot of /dev/rld0g (/home) to 
> /dev/nrst0
> Is it safe to assume that I don't have to create the snapshot with 
> fssconfig first? And that dump takes care of that for us? It's not 
> really clear in dump(8).

Yes and yes.  You could run "fssconfig -lv" and "systat vmstat" during
dump to see a fss device working ...

> Another thing - fss in general (both via dump and by itself) is 
> considered "experimental" but I haven't had much trouble with this until 
> now. Is this because there has been limited testing? Limited resources 
> to maintain/develop it? Perhaps it's not as stable on ports other than 
> i386.

Limited testing. While I'm running snapshot dumps daily on all my
NetBSD machines I'm not aware of others using it on a regular basis.

> I consider this a very important feature and would like to see it 
> considered "stable". It would also be good to get rid of some ironic 
> (albeit funny) documentation in the manual, such as:
>   -x snap-backup
>      Use a snapshot with snap-backup as backup for this dump.  See
>      fss(4) for more details.  Snapshot support is experimental.  Be
>      sure you have a backup before you use it.
> ... from the dump(8) page.

This is NOT meant ironic -- be sure you have a (non-snapshot) dump before
you try it.

> Thanks for your help. Any further clarifications would be most appreciated.

Juergen Hannken-Illjes - - TU Braunschweig 

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