Date: Tue, 15 Jan 2002 21:22:51 -0500 From: Brian T.Schellenberger <bts@babbleon.org> To: "Mike Meyer" <mwm-dated-1011576378.402618@mired.org> Cc: questions@FreeBSD.ORG Subject: Re: HOWTO -- backup onto CDRs? Message-ID: <0a2d11623021012FE4@mail4.nc.rr.com> In-Reply-To: <15428.54969.119254.138926@guru.mired.org> References: <15426.33499.296182.78699@guru.mired.org> <200201152209.g0FM9eI00811@i8k.babbleon.org> <15428.54969.119254.138926@guru.mired.org>
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On Tuesday 15 January 2002 08:26 pm, Mike Meyer wrote:
> Brian T. Schellenberger <bts@babbleon.org> types:
> > > > I did this all the time under Linux; even with a P-450 it worked just
> > > > fine as long as the system wasn't overtaxed (as in, load < 2), using
> > > > the stdin feature of cdrecord. I tried with burncd under FreeBSD and
> > > > had no success, though. Of course, cdrecord doesn't support stdin
> > > > input so I
> >
> > Drat. I meant "Of course, burncd doesn't support stdin . . . ."
>
> Use /dev/stdin as the file to burn. That works with burncd for me.
>
> Brian T. Schellenberger <bts@babbleon.org> types:
> > On Tuesday 15 January 2002 02:48 pm, Gary W. Swearingen wrote:
> > > Anybody know what FS-specific (dump/restore) and non-FS-specific (tar,
> > > cpio, pax, afio) archivers SHOULD do with sockets and named pipes? (Are
> > > there any other kind of weird "files" besides those and block- &
> > > character-special files and symbolic links?)
> >
> > Anyway, these are the only types of files that perl knows aobut; looks
> > pretty complete to me:
>
> There's one other type of screwy file: sparse files. These have
> "holes" where there are no blocks on disk. You can create one
> trivially:
>
> bash-2.05$ dd if=/dev/zero of=y oseek=1000 count=2
> 2+0 records in
> 2+0 records out
> 1024 bytes transferred in 0.000059 secs (17353403 bytes/sec)
> bash-2.05$ ls -l y
> -rw-r--r-- 1 mwm wheel 513024 Jan 15 19:19 y
> bash-2.05$ df .
> Filesystem 1K-blocks Used Avail Capacity Mounted on
> mfs:28 127023 111 116751 0% /tmp
> bash-2.05$ rm y
>
> So I now have a file 513K long that occupies 1K of disk space. In
> fact, the file is on a file system that's only 127K in size.
>
> The nasty part about sparse files is that there is no way to recognize
> them as such without examining the file systems internal
> structures. For instance:
>
> bash-2.05$ wc y
> 0 1 513024 y
>
> The system provides a block full of zeros for the blocks that are
> missing. Tar tries to recognize them as such. Cpio only does that if
> you use the --sparse option.
Are these at all common? For the matter, are they preserved by cp? They
seem like a hyphothetical concern more than a practical one and a nuisance
more than a benefit. But maybe that's just me.
Regardless, if you do a compressed backup they should compress real nicely
(though not as efficiently as the sparse files), though they will spring to
full space on a restore if the backup/restore program isn't clueful about
them.
>
> <mike
--
Brian T. Schellenberger . . . . . . . bts@wnt.sas.com (work)
Brian, the man from Babble-On . . . . bts@babbleon.org (personal)
http://www.babbleon.org
-------> Free Dmitry Sklyarov! (let him go home) <-----------
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