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<HTML
><HEAD
><TITLE
>The mknod command</TITLE
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>5.2. The <B
CLASS="command"
>mknod</B
> command</H1
><P
><B
CLASS="command"
>MAKEDEV</B
> is the preferred way of creating
device files which are not present. However sometimes the
<B
CLASS="command"
>MAKEDEV</B
> script will not know about the device
file you wish to create. This is where the <B
CLASS="command"
>mknod</B
>
command comes in. In order to use <B
CLASS="command"
>mknod</B
> you need
to know the major and minor node numbers for the device you wish to
create. The <TT
CLASS="filename"
>devices.txt</TT
> file in the kernel
source documentation is the canonical source of this
information.</P
><P
>To take an example, let us suppose that our version of the
<B
CLASS="command"
>MAKEDEV</B
> script does not know how to create the
<TT
CLASS="filename"
>/dev/ttyS0</TT
> device file. We need to use
<B
CLASS="command"
>mknod</B
> to create it. We know from looking at the
<TT
CLASS="filename"
>devices.txt</TT
> file that it should be a character
device with major number 4 and minor number 64. So we now know all
we need to create the file.
<TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><FONT
COLOR="#000000"
><PRE
CLASS="screen"
> <TT
CLASS="prompt"
>#</TT
> <TT
CLASS="userinput"
><B
>mknod /dev/ttyS0 c 4 64</B
></TT
>
<TT
CLASS="prompt"
>#</TT
> <TT
CLASS="userinput"
><B
>chown root.dialout /dev/ttyS0</B
></TT
>
<TT
CLASS="prompt"
>#</TT
> <TT
CLASS="userinput"
><B
>chmod 0644 /dev/ttyS0</B
></TT
>
<TT
CLASS="prompt"
>#</TT
> <TT
CLASS="userinput"
><B
>ls -l /dev/ttyS0</B
></TT
>
<TT
CLASS="computeroutput"
>crw-rw---- 1 root dialout 4, 64 Oct 23 18:23 /dev/ttyS0</TT
>
</PRE
></FONT
></TD
></TR
></TABLE
>
As you can see, many more steps are required to create the file. In
this example you can see the process required however. It is
unlikely in the extreme that the ttyS0 file would not be provided by
the <B
CLASS="command"
>MAKEDEV</B
> script, but it suffices to illustrate
the point.</P
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