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>Disks without filesystems</A
></H1
><P
>Not all disks or partitions are used as filesystems.
A swap partition, for example, will not have a filesystem on it.
Many floppies are used in a tape-drive emulating fashion, so that
a <B
CLASS="COMMAND"
>tar</B
> or other file is written directly on
the raw disk, without a filesystem. Linux boot floppies don't
contain a filesystem, only the raw kernel.</P
><P
>Avoiding a filesystem has the advantage of making more of
the disk usable, since a filesystem always has some bookkeeping
overhead. It also makes the disks more easily compatible
with other systems: for example, the <B
CLASS="COMMAND"
>tar</B
>
file format is the same on all systems, while filesystems are
different on most systems. You will quickly get used to disks
without filesystems if you need them. Bootable Linux floppies
also do not necessarily have a filesystem, although that is
also possible.</P
><P
>One reason to use raw disks is to make image copies of them.
For instance, if the disk contains a partially damaged filesystem,
it is a good idea to make an exact copy of it before trying to
fix it, since then you can start again if your fixing breaks things
even more. One way to do this is to use <B
CLASS="COMMAND"
>dd</B
>:
<PRE
CLASS="SCREEN"
><TT
CLASS="PROMPT"
>$</TT
> <TT
CLASS="USERINPUT"
><B
>dd if=/dev/fd0H1440 of=floppy-image</B
></TT
>
<TT
CLASS="COMPUTEROUTPUT"
>2880+0 records in
2880+0 records out</TT
>
<TT
CLASS="PROMPT"
>$</TT
> <TT
CLASS="USERINPUT"
><B
>dd if=floppy-image of=/dev/fd0H1440</B
></TT
>
<TT
CLASS="COMPUTEROUTPUT"
>2880+0 records in
2880+0 records out</TT
>
<TT
CLASS="PROMPT"
>$</TT
></PRE
>
The first <B
CLASS="COMMAND"
>dd</B
> makes an exact image of the
floppy to the file <TT
CLASS="FILENAME"
>floppy-image</TT
>, the second
one writes the image to the floppy. (The user has presumably
switched the floppy before the second command. Otherwise the
command pair is of doubtful usefulness.)</P
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