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@@ -32,9 +32,9 @@
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<para>Using the Udev method, only those devices which are detected by the
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kernel get device nodes created for them. Because these device nodes will be
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created each time the system boots, they will be stored on a <systemitem
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- class="filesystem">tmpfs</systemitem> file system (a virtual file system that
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- resides entirely in system memory). Device nodes do not require much space, so
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- the memory that is used is negligible.</para>
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+ class="filesystem">devtmpfs</systemitem> file system (a virtual file system
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+ that resides entirely in system memory). Device nodes do not require much
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+ space, so the memory that is used is negligible.</para>
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<sect2>
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<title>History</title>
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@@ -87,8 +87,8 @@
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class="filesystem">sysfs</systemitem> filesystem is mounted (on <filename
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class="directory">/sys</filename>), data which the built-in drivers
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registered with <systemitem class="filesystem">sysfs</systemitem> are
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- available to userspace processes and to <command>udevd</command> for device
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- node creation.</para>
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+ available to userspace processes and to <command>udevd</command> for
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+ processing (including modifications to device nodes).</para>
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</sect3>
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@@ -132,24 +132,31 @@
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<sect3>
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<title>Device Node Creation</title>
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- <para>To obtain the right major and minor number for a device, Udev
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- relies on the information provided by <systemitem
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- class="filesystem">sysfs</systemitem> in <filename
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- class="directory">/sys</filename>. For example,
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- <filename>/sys/class/tty/vcs/dev</filename> contains the string
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- <quote>7:0</quote>. This string is used by <command>udevd</command> to
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- create a device node with major number <emphasis>7</emphasis> and minor
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- <emphasis>0</emphasis>. The names and permissions of the nodes created
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- under the <filename class="directory">/dev</filename> directory are
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- determined by rules specified in the files within the <filename
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- class="directory">/etc/udev/rules.d/</filename> directory. These are
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- numbered in a similar fashion to the LFS-Bootscripts package. If
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- <command>udevd</command> can't find a rule for the device it is creating,
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- it will default permissions to <emphasis>660</emphasis> and ownership to
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- <emphasis>root:root</emphasis>. Documentation on the syntax of the Udev
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- rules configuration files are available in
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- <filename>/usr/share/doc/udev-&udev-version;/writing_udev_rules/index.html</filename>
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- </para>
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+ <para>As of Udev-&udev-version;, <command>udevd</command> no longer
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+ creates device files in <filename class="directory">/dev</filename>.
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+ Instead, this must be handled in the kernel, by the <systemitem
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+ class="filesystem">devtmpfs</systemitem> filesystem. Any driver that
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+ wishes to register a device node will go through <systemitem
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+ class="filesystem">devtmpfs</systemitem> (via the driver core) to do it.
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+ When a <systemitem class="filesystem">devtmpfs</systemitem> instance is
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+ mounted on <filename class="directory">/dev</filename>, the device node
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+ will initially be created with a fixed name, permissions, and owner.</para>
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+
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+ <para>A short time later, the kernel will send a uevent to <command>
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+ udevd</command>. Based on the rules specified in the files within the
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+ <filename class="directory">/etc/udev/rules.d</filename>, <filename
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+ class="directory">/lib/udev/rules.d</filename>, and <filename
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+ class="directory">/run/udev/rules.d</filename> directories, <command>
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+ udevd</command> will create additional symlinks to the device node,
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+ or change its permissions, owner, or group, or modify the internal
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+ <command>udevd</command> database entry for that object.</para>
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+
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+ <para>The rules in these three directories are numbered in a similar
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+ fashion to the LFS-Bootscripts package, and all three directories are
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+ merged together. If <command>udevd</command> can't find a rule for the
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+ device it is creating, it will leave the permissions and ownership at
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+ whatever <systemitem class="filesystem">devtmpfs</systemitem> used
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+ initially.</para>
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</sect3>
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@@ -247,12 +254,17 @@
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enhances the functionality of <emphasis>snd-pcm</emphasis> by making the
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sound cards available to OSS applications), configure
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<command>modprobe</command> to load the wrapper after Udev loads the
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- wrapped module. To do this, add an <quote>install</quote> line in any
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+ wrapped module. To do this, add a <quote>softdep</quote> line in any
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<filename>/etc/modprobe.d/<replaceable><filename></replaceable>.conf</filename>
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file. For example:</para>
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-<screen role="nodump"><literal>install snd-pcm /sbin/modprobe -i snd-pcm ; \
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- /sbin/modprobe snd-pcm-oss ; true</literal></screen>
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+<screen role="nodump"><literal>softdep snd-pcm post: snd-pcm-oss</literal></screen>
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+
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+ <para>Note that the <quote>softdep</quote> command also allows
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+ <literal>pre:</literal> dependencies, or a mixture of both
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+ <literal>pre:</literal> and <literal>post:</literal>. See the
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+ <filename>modprobe.d(5)</filename> manual page for more information
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+ on <quote>softdep</quote> syntax and capabilities.</para>
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<para>If the module in question is not a wrapper and is useful by itself,
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configure the <command>modules</command> bootscript to load this
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Bryan Kadzban