kernelconfig-config.html

FreeBSD操作系统的详细使用手册

by which driver.</p>

<pre class="PROGRAMLISTING">
# Wireless NIC cards
device          wlan       # 802.11 support
device          an         # Aironet 4500/4800 802.11 wireless NICs.
device          awi        # BayStack 660 and others
device          wi         # WaveLAN/Intersil/Symbol 802.11 wireless NICs.
#device         wl         # Older non 802.11 Wavelan wireless NIC.
</pre>

<p>Support for various wireless cards.</p>

<pre class="PROGRAMLISTING">
device   mem           # Memory and kernel memory devices
</pre>

<p>The system memory devices.</p>

<pre class="PROGRAMLISTING">
device   io            # I/O device
</pre>

<p>This option allows a process to gain I/O privileges. This is useful in order to write
userland programs that can handle hardware directly. This is required to run the X Window
system.</p>

<pre class="PROGRAMLISTING">
device   random        # Entropy device
</pre>

<p>Cryptographically secure random number generator.</p>

<pre class="PROGRAMLISTING">
device   ether         # Ethernet support
</pre>

<p><var class="LITERAL">ether</var> is only needed if you have an Ethernet card. It
includes generic Ethernet protocol code. Under FreeBSD&nbsp;4.X use the line <var
class="LITERAL">pseudo-device ether</var>.</p>

<pre class="PROGRAMLISTING">
device   sl            # Kernel SLIP
</pre>

<p><var class="LITERAL">sl</var> is for SLIP support. This has been almost entirely
supplanted by PPP, which is easier to set up, better suited for modem-to-modem
connection, and more powerful. With FreeBSD&nbsp;4.X use the line <var
class="LITERAL">pseudo-device sl</var>.</p>

<pre class="PROGRAMLISTING">
device   ppp           # Kernel PPP
</pre>

<p>This is for kernel PPP support for dial-up connections. There is also a version of PPP
implemented as a userland application that uses <var class="LITERAL">tun</var> and offers
more flexibility and features such as demand dialing. With FreeBSD&nbsp;4.X use the line
<var class="LITERAL">pseudo-device ppp</var>.</p>

<pre class="PROGRAMLISTING">
device   tun           # Packet tunnel.
</pre>

<p>This is used by the userland PPP software. See the <a href="userppp.html">PPP</a>
section of this book for more information. With FreeBSD&nbsp;4.X use the line <var
class="LITERAL">pseudo-device tun</var>.</p>

<pre class="PROGRAMLISTING">
<a id="KERNELCONFIG-PTYS" name="KERNELCONFIG-PTYS"></a>
device   pty           # Pseudo-ttys (telnet etc)
</pre>

<p>This is a ``pseudo-terminal'' or simulated login port. It is used by incoming <tt
class="COMMAND">telnet</tt> and <tt class="COMMAND">rlogin</tt> sessions, <b
class="APPLICATION">xterm</b>, and some other applications such as <b
class="APPLICATION">Emacs</b>.</p>

<div class="NOTE">
<blockquote class="NOTE">
<p><b>Note:</b> Under FreeBSD&nbsp;4.X, you have to use the line <var
class="LITERAL">pseudo-device pty <var class="REPLACEABLE">number</var></var>. The <var
class="REPLACEABLE">number</var> after <var class="LITERAL">pty</var> indicates the
number of <var class="LITERAL">pty</var>s to create. If you need more than the default of
16 simultaneous <b class="APPLICATION">xterm</b> windows and/or remote logins, be sure to
increase this number accordingly, up to a maximum of 256.</p>
</blockquote>
</div>

<pre class="PROGRAMLISTING">
device   md            # Memory ``disks''
</pre>

<p>Memory disk pseudo-devices. With FreeBSD&nbsp;4.X use the line <var
class="LITERAL">pseudo-device md</var>.</p>

<pre class="PROGRAMLISTING">
device   gif           # IPv6 and IPv4 tunneling
</pre>

<p>This implements IPv6 over IPv4 tunneling, IPv4 over IPv6 tunneling, IPv4 over IPv4
tunneling, and IPv6 over IPv6 tunneling. Beginning with FreeBSD&nbsp;4.4 the <var
class="LITERAL">gif</var> device is ``auto-cloning'', and you should use the line <var
class="LITERAL">pseudo-device gif</var>. Earlier versions of FreeBSD&nbsp;4.X require a
number, for example <var class="LITERAL">pseudo-device gif 4</var>.</p>

<pre class="PROGRAMLISTING">
device   faith         # IPv6-to-IPv4 relaying (translation)
</pre>

<p>This pseudo-device captures packets that are sent to it and diverts them to the
IPv4/IPv6 translation daemon. With FreeBSD&nbsp;4.X use the line <var
class="LITERAL">pseudo-device faith 1</var>.</p>

<pre class="PROGRAMLISTING">
# The `bpf' device enables the Berkeley Packet Filter.
# Be aware of the administrative consequences of enabling this!
device   bpf           # Berkeley packet filter
</pre>

<p>This is the Berkeley Packet Filter. This pseudo-device allows network interfaces to be
placed in promiscuous mode, capturing every packet on a broadcast network (e.g., an
Ethernet). These packets can be captured to disk and or examined with the <a
href="http://www.FreeBSD.org/cgi/man.cgi?query=tcpdump&sektion=1"><span
class="CITEREFENTRY"><span class="REFENTRYTITLE">tcpdump</span>(1)</span></a> program.
With FreeBSD&nbsp;4.X use the line <var class="LITERAL">pseudo-device bpf</var>.</p>

<div class="NOTE">
<blockquote class="NOTE">
<p><b>Note:</b> The <a
href="http://www.FreeBSD.org/cgi/man.cgi?query=bpf&sektion=4"><span
class="CITEREFENTRY"><span class="REFENTRYTITLE">bpf</span>(4)</span></a> device is also
used by <a href="http://www.FreeBSD.org/cgi/man.cgi?query=dhclient&sektion=8"><span
class="CITEREFENTRY"><span class="REFENTRYTITLE">dhclient</span>(8)</span></a> to obtain
the IP address of the default router (gateway) and so on. If you use DHCP, leave this
uncommented.</p>
</blockquote>
</div>

<pre class="PROGRAMLISTING">
# USB support
#device         uhci          # UHCI PCI-&gt;USB interface
#device         ohci          # OHCI PCI-&gt;USB interface
device          usb           # USB Bus (required)
#device         udbp          # USB Double Bulk Pipe devices
device          ugen          # Generic
device          uhid          # ``Human Interface Devices''
device          ukbd          # Keyboard
device          ulpt          # Printer
device          umass         # Disks/Mass storage - Requires scbus and da
device          ums           # Mouse
device          urio          # Diamond Rio 500 MP3 player
device          uscanner      # Scanners
# USB Ethernet, requires mii
device          aue           # ADMtek USB Ethernet
device          axe           # ASIX Electronics USB Ethernet
device          cue           # CATC USB Ethernet
device          kue           # Kawasaki LSI USB Ethernet
device          rue           # RealTek RTL8150 USB Ethernet
</pre>

<p>Support for various USB devices.</p>

<pre class="PROGRAMLISTING">
# FireWire support
device          firewire      # FireWire bus code
device          sbp           # SCSI over FireWire (Requires scbus and da)
device          fwe           # Ethernet over FireWire (non-standard!)
</pre>

<p>Support for various Firewire devices.</p>

<p>For more information and additional devices supported by FreeBSD, see <tt
class="FILENAME">/usr/src/sys/<var class="REPLACEABLE">i386</var>/conf/NOTES</tt>.</p>

<div class="SECT2">
<h2 class="SECT2"><a id="AEN10012" name="AEN10012">8.4.1 Large Memory Configurations
(<acronym class="ACRONYM">PAE</acronym>)</a></h2>

<p>Large memory configuration machines require access to more than the 4 gigabyte limit
on User+Kernel Virtual Address (<acronym class="ACRONYM">KVA</acronym>) space. Due to
this limitation, Intel added support for 36-bit physical address space access in the
<span class="TRADEMARK">Pentium</span>&reg; Pro and later line of CPUs.</p>

<p>The Physical Address Extension (<acronym class="ACRONYM">PAE</acronym>) capability of
the <span class="TRADEMARK">Intel</span>&reg; <span class="TRADEMARK">Pentium</span> Pro
and later CPUs allows memory configurations of up to 64 gigabytes. FreeBSD provides
support for this capability via the <var class="OPTION">PAE</var> kernel configuration
option, available in the 4.X series of FreeBSD beginning with 4.9-RELEASE and in the 5.X
series of FreeBSD beginning with 5.1-RELEASE. Due to the limitations of the Intel memory
architecture, no distinction is made for memory above or below 4 gigabytes. Memory
allocated above 4 gigabytes is simply added to the pool of available memory.</p>

<p>To enable <acronym class="ACRONYM">PAE</acronym> support in the kernel, simply add the
following line to your kernel configuration file:</p>

<pre class="PROGRAMLISTING">
options            PAE
</pre>

<div class="NOTE">
<blockquote class="NOTE">
<p><b>Note:</b> The <acronym class="ACRONYM">PAE</acronym> support in FreeBSD is only
available for <span class="TRADEMARK">Intel</span> IA-32 processors. It should also be
noted, that the <acronym class="ACRONYM">PAE</acronym> support in FreeBSD has not
received wide testing, and should be considered beta quality compared to other stable
features of FreeBSD.</p>
</blockquote>
</div>

<p><acronym class="ACRONYM">PAE</acronym> support in FreeBSD has a few limitations:</p>

<ul>
<li>
<p>A process is not able to access more than 4 gigabytes of VM space.</p>
</li>

<li>
<p><acronym class="ACRONYM">KLD</acronym> modules cannot be loaded into a <acronym
class="ACRONYM">PAE</acronym> enabled kernel, due to the differences in the build
framework of a module and the kernel.</p>
</li>

<li>
<p>Device drivers that do not use the <a
href="http://www.FreeBSD.org/cgi/man.cgi?query=bus_dma&sektion=9"><span
class="CITEREFENTRY"><span class="REFENTRYTITLE">bus_dma</span>(9)</span></a> interface
will cause data corruption in a <acronym class="ACRONYM">PAE</acronym> enabled kernel and
are not recommended for use. For this reason, the <tt class="FILENAME">PAE</tt> kernel
configuration file is provided in FreeBSD 5.X, which excludes all drivers not known to
work in a <acronym class="ACRONYM">PAE</acronym> enabled kernel.</p>
</li>

<li>
<p>Some system tunables determine memory resource usage by the amount of available
physical memory. Such tunables can unnecessarily over-allocate due to the large memory
nature of a <acronym class="ACRONYM">PAE</acronym> system. One such example is the <var
class="OPTION">kern.maxvnodes</var> sysctl, which controls the maximum number of vnodes
allowed in the kernel. It is advised to adjust this and other such tunables to a
reasonable value.</p>
</li>

<li>
<p>It might be necessary to increase the kernel virtual address (<acronym
class="ACRONYM">KVA</acronym>) space or to reduce the amount of specific kernel resource
that is heavily used (see above) in order to avoid <acronym class="ACRONYM">KVA</acronym>
exhaustion. The <var class="OPTION">KVA_PAGES</var> kernel option can be used for
increasing the <acronym class="ACRONYM">KVA</acronym> space.</p>
</li>
</ul>

<p>For performance and stability concerns, it is advised to consult the <a
href="http://www.FreeBSD.org/cgi/man.cgi?query=tuning&sektion=7"><span
class="CITEREFENTRY"><span class="REFENTRYTITLE">tuning</span>(7)</span></a> manual page.
The <a href="http://www.FreeBSD.org/cgi/man.cgi?query=pae&sektion=4"><span
class="CITEREFENTRY"><span class="REFENTRYTITLE">pae</span>(4)</span></a> manual page
contains up-to-date information on FreeBSD's <acronym class="ACRONYM">PAE</acronym>
support.</p>
</div>
</div>

<h3 class="FOOTNOTES">Notes</h3>

<table border="0" class="FOOTNOTES" width="100%">
<tr>
<td align="LEFT" valign="TOP" width="5%"><a id="FTN.AEN9627" name="FTN.AEN9627"
href="kernelconfig-config.html#AEN9627"><span class="footnote">[1]</span></a></td>
<td align="LEFT" valign="TOP" width="95%">
<p>The auto-tuning algorithm sets <var class="LITERAL">maxusers</var> equal to the amount
of memory in the system, with a minimum of 32, and a maximum of 384.</p>
</td>
</tr>
</table>

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