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>Chapter 6. Configure <SPAN
CLASS="PRODUCTNAME"
>getty</SPAN
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><H1
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><A
NAME="GETTY-INIT"
></A
>6.1. <SPAN
CLASS="PRODUCTNAME"
>init</SPAN
> system</H1
><P
>The file <TT
CLASS="FILENAME"
>/etc/inittab</TT
> contains the
background programs that used to keep the system running. One of
these programs is one <SPAN
CLASS="APPLICATION"
>getty</SPAN
> process per
serial port.</P
><DIV
CLASS="FIGURE"
><A
NAME="GETTY-INIT-INITTAB"
></A
><P
><B
>Figure 6-3. <SPAN
CLASS="APPLICATION"
>getty</SPAN
> is started by
<SPAN
CLASS="APPLICATION"
>init</SPAN
>, based upon an entry in
<TT
CLASS="FILENAME"
>/etc/inittab</TT
></B
></P
><TABLE
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><TD
><FONT
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><PRE
CLASS="SCREEN"
>co:2345:respawn:/sbin/getty ttyS0 CON9600 vt102</PRE
></FONT
></TD
></TR
></TABLE
></DIV
><P
>Each field in <TT
CLASS="FILENAME"
>inittab</TT
> is separated by a
colon and contains:</P
><P
></P
><DIV
CLASS="VARIABLELIST"
><DL
><DT
><TT
CLASS="LITERAL"
>co</TT
></DT
><DD
><P
>Arbitrary entry for <TT
CLASS="FILENAME"
>inittab</TT
>. As long
as this entry doesn't appear anywhere else in
<TT
CLASS="FILENAME"
>inittab</TT
>, you're okay. We named this entry
<TT
CLASS="LITERAL"
>co</TT
> because it's for the console.</P
><P
><SPAN
CLASS="PRODUCTNAME"
>Red Hat Linux</SPAN
>
<SPAN
CLASS="PRODUCTNUMBER"
>7.3</SPAN
> has a program called
<SPAN
CLASS="APPLICATION"
>kudzu</SPAN
> which configures the system
when it is booted. <SPAN
CLASS="APPLICATION"
>kudzu</SPAN
> treats an
<TT
CLASS="FILENAME"
>inittab</TT
> entry of <TT
CLASS="LITERAL"
>co</TT
>
specially, setting it for the attached monitor and keyboard or
the serial console. Hardcoding the value of
<TT
CLASS="FILENAME"
>co</TT
> prevents this behaviour.</P
></DD
><DT
><TT
CLASS="LITERAL"
>2345</TT
></DT
><DD
><P
>Run levels where this entry gets started. Run levels 2,
3, 4 and 5 can be used for an operational system,
<SPAN
CLASS="APPLICATION"
>getty</SPAN
> should not be used in other run
levels. The serial console still works in run level 1 (or
single user mode) even without a
<SPAN
CLASS="APPLICATION"
>getty</SPAN
>.</P
></DD
><DT
><TT
CLASS="LITERAL"
>respawn</TT
></DT
><DD
><P
>Re-run the program if it dies. We want this to happen so
that a new <TT
CLASS="PROMPT"
>login</TT
> prompt will appear when you
log out of the console.</P
></DD
><DT
><TT
CLASS="LITERAL"
>/sbin/getty ttyS0 CON9600 vt102</TT
></DT
><DD
><P
>The command to run. In this case, we're telling
<SPAN
CLASS="APPLICATION"
>getty</SPAN
> to connect to <TT
CLASS="FILENAME"
>/dev/ttyS0</TT
> using the settings for
<TT
CLASS="LITERAL"
>CON9600</TT
> which exists in
<TT
CLASS="FILENAME"
>/etc/gettydefs</TT
>. This entry represents a
terminal running at 9600<SPAN
CLASS="ABBREV"
>bps</SPAN
>. Initially assume
that the terminal is a later-model
<SPAN
CLASS="PRODUCTNAME"
><SPAN
CLASS="ACRONYM"
>VT100</SPAN
></SPAN
>.</P
></DD
></DL
></DIV
><P
>After changing <TT
CLASS="FILENAME"
>/etc/inittab</TT
> restart
<SPAN
CLASS="APPLICATION"
>init</SPAN
> with</P
><DIV
CLASS="INFORMALFIGURE"
><A
NAME="AEN1544"
></A
><P
></P
><TABLE
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><TR
><TD
><FONT
COLOR="#000000"
><PRE
CLASS="SCREEN"
><B
CLASS="COMMAND"
>telinit q</B
></PRE
></FONT
></TD
></TR
></TABLE
><P
></P
></DIV
><P
>An alternative is to send the hangup signal to
<SPAN
CLASS="APPLICATION"
>init</SPAN
> with the command <B
CLASS="COMMAND"
>kill -HUP
1</B
>. This is not recommended: if you make a typing mistake
and actually kill <SPAN
CLASS="APPLICATION"
>init</SPAN
> then your system
will suddenly halt.</P
><DIV
CLASS="NOTE"
><P
></P
><TABLE
CLASS="NOTE"
WIDTH="100%"
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><TD
WIDTH="25"
ALIGN="CENTER"
VALIGN="TOP"
><IMG
SRC="../images/note.gif"
HSPACE="5"
ALT="Note"></TD
><TH
ALIGN="LEFT"
VALIGN="CENTER"
><B
>Comments in <TT
CLASS="FILENAME"
>inittab</TT
> and Red Hat's
<SPAN
CLASS="APPLICATION"
>kudzu</SPAN
></B
></TH
></TR
><TR
><TD
> </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><P
><SPAN
CLASS="APPLICATION"
>kudzu</SPAN
> uses the
<TT
CLASS="LITERAL"
>#</TT
> line comment to activate and deactivate the
<SPAN
CLASS="APPLICATION"
>getty</SPAN
>s for the attached monitor and
keyboard and for the serial port. To prevent a genuine comment
from becoming confused with a line saved by
<SPAN
CLASS="APPLICATION"
>kudzu</SPAN
> use <TT
CLASS="LITERAL"
>##</TT
> at the
start of a line of genuine comments.</P
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