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

Steve Sandau ssandau at gwi.net
Thu Feb 12 16:37:16 CST 2004

> 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).

I always thought dd was "device-to-device" copy. And the bit-by-bit copy 
is indeed a feature. I can use dd to email a boot disk as a floppy 
image, or to put a floppy image back on a disk. I've also cloned an AIX 
hard drive before I messed with it. dd copied the bootblock and all, so 
I could put the image I made back on another herd drive and it was 
immediately bootable. I had no way to reinstall the OS, since it was on 
an eBay-bought 6611 router. I cracked the passwords without worrying 
about damaging the original disk.


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