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Re: Is there a good "dd for dummies" tutorial around?

From Tauno Voipio <tauno.voipio@notused.fi.invalid>
Newsgroups comp.os.linux.misc
Subject Re: Is there a good "dd for dummies" tutorial around?
Date 2016-02-20 20:24 +0200
Organization A noiseless patient Spider
Message-ID <naaarc$lpk$1@dont-email.me> (permalink)
References <9be980ce-21a2-4d14-bfb4-ad96dcd9a5a5@googlegroups.com>

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On 20.2.16 20:04, pureheart@pacbell.net wrote:
> This is probably considered basic stuff but I'm still having trouble understanding dd.
>
> In particular, why do the things it writes/reads to have to be *un*mounted?
>
> How does the system even know that the device exists if it's not mounted?
>
> What happens if you *do* write to a mounted device.
>
> So far I've read about six dd how-tos, but I have not had the mounting explained to my feeble mind's satisfaction.
>
> Anyone have a good url or simple explanation?
>
> Pureheart in Aptos
>

Actually, this is a question of copying filesystem images. dd
is the tool often used for it, but the considerations apply
to other methods of copying, as well.

If a filesystem image is mounted, the filesystem handler
may be changing its contents, and it relies on the image
staying intact from other writers.

The unmount requirement applies to all filesystem images,
be they disk partitions or loopback mount files.

In modern Linux distributions there is a pseudo-filesystem
/proc, which is a peekhole into kernel internals. You'll
see all disk partitions known to the kernel by reading
/proc/partitions:

   cat /proc/partitions

-- 

-TV

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Thread

Is there a good "dd for dummies" tutorial around? pureheart@pacbell.net - 2016-02-20 10:04 -0800
  Re: Is there a good "dd for dummies" tutorial around? Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2016-02-20 20:24 +0200
  Re: Is there a good "dd for dummies" tutorial around? William Unruh <unruh@invalid.ca> - 2016-02-20 18:26 +0000
  Re: Is there a good "dd for dummies" tutorial around? Robert Heller <heller@deepsoft.com> - 2016-02-20 12:40 -0600
  Re: Is there a good "dd for dummies" tutorial around? Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2016-02-20 14:10 -0500
  Re: Is there a good "dd for dummies" tutorial around? "Carlos E. R." <robin_listas@invalid.es> - 2016-02-22 02:59 +0100
    Re: Is there a good "dd for dummies" tutorial around? "Carlos E.R." <robin_listas@invalid.es> - 2016-02-22 04:39 +0100
      Re: Is there a good "dd for dummies" tutorial around? pureheart@pacbell.net - 2016-02-24 15:55 -0800
        Re: Is there a good "dd for dummies" tutorial around? "Carlos E. R." <robin_listas@invalid.es> - 2016-02-26 03:39 +0100
          Re: Is there a good "dd for dummies" tutorial around? pureheart@pacbell.net - 2016-02-29 18:05 -0800
            Re: Is there a good "dd for dummies" tutorial around? The Natural Philosopher <tnp@invalid.invalid> - 2016-03-01 02:45 +0000
            Re: Is there a good "dd for dummies" tutorial around? "Carlos E.R." <robin_listas@invalid.es> - 2016-03-01 11:14 +0100

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