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<H1><A NAME="SECTION00590000000000000000">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 <tt>tar</tt><A NAME="1766"> </A> 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>
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 <tt>tar</tt><A NAME="1768"> </A> 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>
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 <tt>dd</tt><A NAME="1770"> </A>:
<BLOCKQUOTE> <TT>
<code>$</code> <I>dd if=/dev/fd0H1440 of=floppy-image</I> <BR>
<code>2880+0 records in</code> <BR>
<code>2880+0 records out</code> <BR>
<code>$</code> <I>dd if=floppy-image of=/dev/fd0H1440 </I> <BR>
<code>2880+0 records in</code> <BR>
<code>2880+0 records out</code> <BR>
<code>$</code>
</TT></BLOCKQUOTE>
The first <tt>dd</tt><A NAME="1772"> </A> makes an exact image of the floppy to the file
<tt>floppy-image</tt><A NAME="1774"> </A>, 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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<P><ADDRESS>
<I>Lars Wirzenius <BR>
Sat Nov 15 02:32:11 EET 1997</I>
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