[rescue] Block size and the single DD - more test results

Caleb Shay caleb at webninja.com
Thu Feb 12 16:10:27 CST 2004

On 2004-02-12 16:44:01 -0500 Sheldon T. Hall <shel at cmhcsys.com> wrote:


> However, if dd reads the whole slice, it would seem to be a poor 
> choice of
> backups of small filesystems on big disks/slices ... yet many folks 
> use it.
> Anyone want to tell me what's going on here?

As far as I know, the true meaning of 'dd' has been lost to the mists 
of time, but it likely stood for something along the lines of 'disk 
duplicator' or 'data dumper' or something along those lines.  It has 
no real concept of a file, or even a filesystem.  dd basically does a 
byte-for-byte copy of a device/slice/partition, it has no concept of 
what is actually on the filesystem.  This is a feature.  It allowed me 
to use dd to make clones of systems that the underlying OS knows 
nothing about (ie, using linux to make clones of a Windows 2000 
installation for corporate roll-out, or making _bootable_ backups of 
my IRIX install CDs from linux).

It is NOT a backup utility in the normal sense of backup<->recovery, 
but it rocks for system imaging.

What dd+tape gives you (assuming your hardware/OS support it) is the 
ability to make bootable tapes, which is pretty damn cool for bare 
metal recovery.

For backup/restore of files you need something that understands what 
files are, ie.  [sg]tar/zip/cpio/etc



> -Shel
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