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diff --git a/chapter06/makedev.xml b/chapter06/makedev.xml index 0763e8c8f..3fce5fb6a 100644 --- a/chapter06/makedev.xml +++ b/chapter06/makedev.xml @@ -1,8 +1,9 @@ -<sect1 id="ch-system-MAKEDEV" xreflabel="Makedev"> -<title>Creating devices with Makedev-&makedev-version;</title> -<?dbhtml filename="makedev.html" dir="chapter06"?> +<sect1 id="ch-system-MAKEDEV" xreflabel="Make_devices"> +<title>Creating devices with Make_devices-&makedev-version;</title> +<?dbhtml filename="makedevices.html" dir="chapter06"?> -<para>The MAKEDEV package contains a script for making device nodes.</para> +<para>The Make_devices package contains a script for creating device +nodes.</para> <screen>&buildtime; &makedev-time; &diskspace; &makedev-compsize;</screen> @@ -15,62 +16,79 @@ <sect2> <title>Making devices</title> -<para>Note that unpacking the <filename>MAKEDEV-&makedev-version;.bz2</filename> -file doesn't create a directory for you to <command>cd</command> into, as -the file contains only a shell script.</para> +<para>Note that unpacking the +<filename>make_devices-&makedev-version;.bz2</filename> file doesn't +create a directory for you to <command>cd</command> into, as the file +contains only a shell script.</para> + +<para>Install the <filename>make_devices</filename> script:</para> + +<screen><userinput>bzcat make_devices-&makedev-version;.bz2 > /dev/make_devices +chmod 754 /dev/make_devices</userinput></screen> + +<para>Device nodes are special files: things that can generate or receive data. +They usually correspond to physical pieces of hardware, and can be created by +issuing commands of the form: <command>mknod -m mode name type major +minor</command>. In such a command, <emphasis>mode</emphasis> is the usual +octal read/write/execute permissions triplet, and <emphasis>name</emphasis> is +the name of the device file to be created. It may seem surprising, but the +device name is actually arbitrary, except that most programs rely on devices +such as <filename>/dev/null</filename> having their usual names. The remaining +three parameters tell the kernel what piece of hardware the device node +actually refers to. The <emphasis>type</emphasis> is a letter, either b or c, +indicating whether the device is accessed in blocks (such as a hard disk) or +character by character (such as the console). And <emphasis>major</emphasis> +and <emphasis>minor</emphasis> are numbers, together forming a code that +identifies the device to the kernel. A list of the currently assigned device +numbers for Linux can be found in the file <filename>devices.txt</filename> in +the <filename class="directory">Documentation</filename> subdirectory of the +kernel sources.</para> + +<para>Note that the same major/minor combination are usually assigned to both a +block and a character device. These are, however, completely unrelated devices +that cannot be interchanged. A device is identified by the type/major/minor +triple, not just the major/minor pair, so when creating a device node it is +important to choose the correct <emphasis>type</emphasis> of device.</para> + +<para>Because looking up the type/major/minor triples and using +<command>mknod</command> manually is tedious and error-prone, the +<filename>make_devices</filename> script has been created. It contains a whole +series of <command>mknod</command> commands, one for each device, complete with +recommended name, permissions and group assignment. It has been set up so that +only a minimal set of commonly used devices is enabled and the other lines are +commented out. You should open <filename>make_devices</filename> in an editor +and customize it to your needs. This takes some time, but is very simple. When +you are satisfied, run the script to create the device files:</para> -<para>Install the <command>MAKEDEV</command> script:</para> - -<screen><userinput>bzcat MAKEDEV-&makedev-version;.bz2 > /dev/MAKEDEV -chmod 754 /dev/MAKEDEV</userinput></screen> +<screen><userinput>cd /dev +./make_devices</userinput></screen> -<para>Run the script to create the device files:</para> +<para>(The FHS states that there should be a <filename>MAKEDEV</filename> +script present in the <filename class="directory">/dev</filename> directory. +But the FHS is mistaken: it should not dictate anything about files, and limit +itself to directories.)</para> -<screen><userinput>cd /dev -./MAKEDEV -v generic-nopty</userinput></screen> - -<para>The meaning of the arguments:</para> - -<itemizedlist> -<listitem><para><userinput>-v</userinput>: This tells the script to run in -verbose mode.</para></listitem> - -<listitem><para><userinput>generic-nopty</userinput>: This instructs -<command>MAKEDEV</command> to create a generic selection of commonly used -device special files, except for the ptyXX and ttyXX range of files. We don't -need those files because we are going to use Unix98 PTYs via the -<emphasis>devpts</emphasis> file system.</para></listitem> -</itemizedlist> - -<para>If it turns out that some special device <filename>zzz</filename> that -you need is missing, try running <userinput>./MAKEDEV -v zzz</userinput>. -Alternatively, you may create devices via the <command>mknod</command> -program. Please refer to its man and info pages if you need more -information.</para> - -<para>If you wish your system to be FHS-compliant, then the -<filename>MAKEDEV</filename> script has to remain present in the -<filename class="directory">/dev</filename> directory. This way it is always -available for making extra device nodes.</para> - -<para>Additionally, if you were unable to mount the devpts file system earlier -in <xref linkend="ch-system-proc"/>, now is the time to try the alternatives. If -your kernel supports the devfs file system, run the following command to mount +<para>If you had success with mounting the devpts file system earlier in <xref +linkend="ch-system-proc"/>, you can continue with the next section. If you were +unable to mount devpts, now is the time to try the alternatives. If your kernel +supports the devfs file system, run the following command to mount devfs:</para> <screen><userinput>mount -t devfs devfs /dev</userinput></screen> <para>This will mount the devfs file system over the top of the new static -<filename>/dev</filename> structure. This poses no problems, as the device nodes -created are still present, they are just hidden by the new devfs -file system.</para> - -<para>If this still doesn't work, the only option left is to use the MAKEDEV -script to create the ptyXX and ttyXX range of files that would otherwise not be -needed. Ensure you are still in the <filename>/dev</filename> directory then run -<userinput>./MAKEDEV -v pty</userinput>. The downside of this is, we are -creating an extra 512 device special files which will not be needed when we -finally boot into the finished LFS system.</para> +<filename>/dev</filename> structure. This poses no problems, as the device +nodes created are still present, they are just hidden by the new devfs file +system.</para> + +<para>If that didn't work either, the only option left is to create a few ptyXX +and ttyXX device nodes. To do this, open <filename>make_devices</filename> in +your editor, go to the section "Pseudo-TTY masters" and enable as many ptyXX +devices as you think you will need (one for every active xterm, ssh connection, +telnet connection, and so on). In the immediately following section "Pseudo-TTY +slaves", enable the corresponding ttyXX devices. When you are done, rerun +<command>./make_devices</command> from inside <filename>/dev</filename> to have +it create the new devices.</para> </sect2> |