static/freebsd/man4/nvram.4 3.html


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<table class="head">
  <tr>
    <td class="head-ltitle">NVRAM(4)</td>
    <td class="head-vol">Device Drivers Manual</td>
    <td class="head-rtitle">NVRAM(4)</td>
  </tr>
</table>
<div class="manual-text">
<section class="Sh">
<h1 class="Sh" id="NAME"><a class="permalink" href="#NAME">NAME</a></h1>
<p class="Pp"><code class="Nm">nvram</code> &#x2014;
    <span class="Nd">non-volatile RAM</span></p>
</section>
<section class="Sh">
<h1 class="Sh" id="SYNOPSIS"><a class="permalink" href="#SYNOPSIS">SYNOPSIS</a></h1>
<p class="Pp">To compile this driver into the kernel, place the following line
    in your kernel configuration file:</p>
<div class="Bd Pp Bd-indent"><code class="Cd">device nvram</code></div>
<p class="Pp">Alternatively, to load the driver as a module at boot time, place
    the following line in <a class="Xr">loader.conf(5)</a>:</p>
<div class="Bd Pp Bd-indent Li">
<pre>nvram_load=&quot;YES&quot;</pre>
</div>
</section>
<section class="Sh">
<h1 class="Sh" id="DESCRIPTION"><a class="permalink" href="#DESCRIPTION">DESCRIPTION</a></h1>
<p class="Pp">The <code class="Nm">nvram</code> driver provides access to BIOS
    configuration NVRAM on i386 and amd64 systems.</p>
<p class="Pp">PC motherboard uses a small non-volatile memory to store BIOS
    settings which is usually part of its clock chip and sometimes referred as
    &#x201C;CMOS SRAM&#x201D;. This driver exposes bytes 14 through 128 of the
    NVRAM, or a total of 114 bytes, at offset zero of the device file
    <span class="Pa">/dev/nvram</span>.</p>
<p class="Pp">This driver is useful for cloning machines that shares the same
    hardware configuration and need same BIOS setting tweaks.</p>
</section>
<section class="Sh">
<h1 class="Sh" id="IMPLEMENTATION_NOTES"><a class="permalink" href="#IMPLEMENTATION_NOTES">IMPLEMENTATION
  NOTES</a></h1>
<p class="Pp">The BIOS NVRAM's bytes 16 through 31 are checksummed at byte 32.
    This driver <a class="permalink" href="#does"><i class="Em" id="does">does
    not</i></a> take care for these checksums.</p>
</section>
<section class="Sh">
<h1 class="Sh" id="EXAMPLES"><a class="permalink" href="#EXAMPLES">EXAMPLES</a></h1>
<p class="Pp">Backup existing BIOS NVRAM to
  <span class="Pa">nvram.bin</span>:</p>
<p class="Pp"></p>
<div class="Bd Bd-indent"><code class="Li">dd if=/dev/nvram
  of=nvram.bin</code></div>
<p class="Pp">Restore BIOS NVRAM from <span class="Pa">nvram.bin</span>:</p>
<p class="Pp"></p>
<div class="Bd Bd-indent"><code class="Li">dd if=nvram.bin
  of=/dev/nvram</code></div>
</section>
<section class="Sh">
<h1 class="Sh" id="SEE_ALSO"><a class="permalink" href="#SEE_ALSO">SEE
  ALSO</a></h1>
<p class="Pp"><a class="Xr">dd(1)</a></p>
</section>
<section class="Sh">
<h1 class="Sh" id="HISTORY"><a class="permalink" href="#HISTORY">HISTORY</a></h1>
<p class="Pp">The <code class="Nm">nvram</code> device driver first appeared in
    <span class="Ux">FreeBSD 6.4</span>.</p>
</section>
<section class="Sh">
<h1 class="Sh" id="AUTHORS"><a class="permalink" href="#AUTHORS">AUTHORS</a></h1>
<p class="Pp">The <code class="Nm">nvram</code> device driver was written by
    <span class="An">Peter Wemm</span>. This manual page was written by
    <span class="An">Xin LI</span>.</p>
</section>
</div>
<table class="foot">
  <tr>
    <td class="foot-date">February 8, 2010</td>
    <td class="foot-os">FreeBSD 15.0</td>
  </tr>
</table>