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

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On Sunday, February 21, 2016 at 7:45:17 PM UTC-8, Carlos E.R. wrote:
> On 2016-02-22 02:59, Carlos E. R. wrote:
> > On 2016-02-20 19:04, .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?
> > 
> > They don't. It depends on what you want to do.
> 
> To clarify.
> 
>  dd if=/tmp/somefile of=/tmp/someotherfile
> 
> needs the filesystem be mounted. while:
> 
>  dd if=/dev/sdb1 of=/tmp/imageofsdb1
> 
> can run while sdb1 is mounted, but the resulting image will be "dirty";
> ie, it will at need an fsck before being used. And if something changes
> in the mounted sdb1 while the copy runs, the resulting image will be
> inconsistent.
> 
> This one:
> 
>  dd if=/tmp/imageofsdb1 of=/dev/sdb1
> 
> might (at worst) provoke a crash of some kind if sdb1 is mounted while
> you write to it this way.
> 
> 
> None of that is specific to 'dd', but to copy and filesystem operations,
> regardless of whatever tool you use.
> 
> In fact, all those operations can be done with a plain "cp", ie, the
> copy file program.
> 
> -- 
> Cheers, Carlos.
> 
> --- news://freenews.netfront.net/ - complaints: news@netfront.net ---

Hi Carlos.
Thank you and all the others for the replies.
I have no task in mind, I just have a hard time understanding how it can do *anything* to unmounted drives....the replies have helped set me straight, Mr. Heller's reply, especially.

Thanks, guys.
pH

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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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