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<span id="Optical-media"></span><div class="header">
<p>
Next: <a href="Examples.html" accesskey="n" rel="next">Examples</a>, Previous: <a href="Emergency-save.html" accesskey="p" rel="prev">Emergency save</a>, Up: <a href="index.html" accesskey="u" rel="up">Top</a> &nbsp; [<a href="Concept-index.html" title="Index" rel="index">Index</a>]</p>
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<hr>
<span id="Copying-CD_002dROMs-and-DVDs"></span><h2 class="chapter">9 Copying CD-ROMs and DVDs</h2>
<span id="index-optical-media"></span>

<p>Ddrescue may be better than dd for copying recordable CD-ROMs because
the two lead out sectors at the end of some of them may cause a read
error that prevents the whole last record from being copied by dd,
potentially losing data. Also dd may create an image larger than the
original if the &lsquo;<samp>sync</samp>&rsquo; conversion and a block size larger than the
sector size are specified.
</p>
<p>In the special case of reading CD-ROMs (but not DVDs), the specialized
tool dvdisaster may be a better option than ddrescue for recovering data
because dvdisaster can read and analyze raw CD sectors, which ddrescue
can&rsquo;t.
</p>
<p>Recordable CD and DVD media keep their data only for a finite time
(typically for some years). After that time, data loss develops slowly
with read errors growing from the outer media region towards the inside.
Just make two (or more) copies of every important CD-ROM/DVD you burn so
that you can later recover them with ddrescue.
</p>
<p>If you have only one copy of a CD-ROM or DVD that fails when being
copied, and if you have access to multiple optical media drives, you
have a better chance of recovering the bad sectors since one drive may
fail to read a particular sector, but another drive might be able to
squeeze the data out of it, depending on the laser frequency and the
sensitivity of the laser-sensor that reads the reflected laser light.
</p>
<br>
<p>Example 1: Rescue a CD-ROM in /dev/cdrom.
</p>
<div class="example">
<pre class="example">ddrescue -n -b2048 /dev/cdrom cdimage mapfile
ddrescue -d -r1 -b2048 /dev/cdrom cdimage mapfile
  (if bad-sector size is zero, cdimage now contains a complete image
   of the CD-ROM and you can write it to a blank CD-ROM)
</pre></div>

<br>
<p>Example 2: Rescue a CD-ROM in /dev/cdrom from two copies.
</p>
<div class="example">
<pre class="example">ddrescue -n -b2048 /dev/cdrom cdimage mapfile
ddrescue -d -b2048 /dev/cdrom cdimage mapfile
  (insert second copy in the CD drive)
ddrescue -d -r1 -b2048 /dev/cdrom cdimage mapfile
  (if bad-sector size is zero, cdimage now contains a complete image
   of the CD-ROM and you can write it to a blank CD-ROM)
</pre></div>

<br>
<p>Example 3: Rescue a CD-ROM in /dev/cdrom using two CD drives from two
different computers, writing the image into an USB drive mounted on
/mnt/mem.
</p>
<div class="example">
<pre class="example">ddrescue -n -b2048 /dev/cdrom /mnt/mem/cdimage /mnt/mem/mapfile
ddrescue -d -r1 -b2048 /dev/cdrom /mnt/mem/cdimage /mnt/mem/mapfile
  (umount the USB drive and move both USB drive and CD-ROM to second
   computer)
ddrescue -d -r1 -b2048 /dev/cdrom /mnt/mem/cdimage /mnt/mem/mapfile
  (if bad-sector size is zero, /mnt/mem/cdimage now contains a complete
   image of the CD-ROM and you can write it to a blank CD-ROM)
</pre></div>

<br>
<p>Example 4: Merge the partially recovered images of 3 identical DVDs
using their mapfiles as domain mapfiles.
</p>
<div class="example">
<pre class="example">ddrescue -m mapfile1 dvdimage1 dvdimage mapfile
ddrescue -m mapfile2 dvdimage2 dvdimage mapfile
ddrescue -m mapfile3 dvdimage3 dvdimage mapfile
  (if bad-sector size is zero, dvdimage now contains a complete image
   of the DVD and you can write it to a blank DVD)
</pre></div>

<br>
<span id="lziprecover_002dexample"></span><p>Example 5: Rescue a lzip compressed backup from two copies on CD-ROM
with error-checked merging of copies.
(See the
<a href="http://www.nongnu.org/lzip/manual/lziprecover_manual.html">lziprecover manual</a>
for details about lziprecover).
</p>
<div class="example">
<pre class="example">ddrescue -d -r1 -b2048 /dev/cdrom cdimage1 mapfile1
mount -t iso9660 -o loop,ro cdimage1 /mnt/cdimage
cp /mnt/cdimage/backup.tar.lz rescued1.tar.lz
umount /mnt/cdimage
  (insert second copy in the CD drive)
ddrescue -d -r1 -b2048 /dev/cdrom cdimage2 mapfile2
mount -t iso9660 -o loop,ro cdimage2 /mnt/cdimage
cp /mnt/cdimage/backup.tar.lz rescued2.tar.lz
umount /mnt/cdimage
lziprecover -m -v -o backup.tar.lz rescued1.tar.lz rescued2.tar.lz
  Input files merged successfully.
lziprecover -tv backup.tar.lz
  backup.tar.lz: ok
</pre></div>


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