Digital or Disk or Discrete Dump (dd)

dd is like cat except it can read and write in discrete blocks.

 
   dd if=in-file of=out-file [ bs=block-size ] 
      [ count=number-of-blocks ] [ seek=output-offset]
      [ skip=input-offset ]

You must specify an input file and an output file with the if= and of= options.

 
Example: Save a large file to mutiple floppy-disks:

dd if=large_file of=/dev/fd0 bs=1440 count=1 skip=0

...change floppy...

dd if=large_file of=/dev/fd0 bs=1440 count=1 skip=1
 
...change floppy...

dd if=large_file of=/dev/fd0 bs=1440 count=1 skip=2

...

---------

Then recover the large file with:

dd if=/dev/fd0 of=floppy_01 bs=1440 count=1 skip=0

...first floppy...

dd if=/dev/fd0 of=floppy_02 bs=1440 count=1 skip=0

...next floppy...

dd if=/dev/fd0 of=floppy_03 bs=1440 count=1 skip=0

...next floppy...

.
.
.

cat >>large_file floppy_*

To create a boot floppy, find the boot.img file on ftp.suse.com or ftp.redhat.com, etc and run:

     dd if=boot.img of=/dev/fd0