svn commit: r44786 - head/en_US.ISO8859-1/books/handbook/serialcomms
Dru Lavigne
dru at FreeBSD.org
Wed May 7 18:12:22 UTC 2014
Author: dru
Date: Wed May 7 18:12:21 2014
New Revision: 44786
URL: http://svnweb.freebsd.org/changeset/doc/44786
Log:
Finish editorial review of Terminals.
Sponsored by: iXsystems
Modified:
head/en_US.ISO8859-1/books/handbook/serialcomms/chapter.xml
Modified: head/en_US.ISO8859-1/books/handbook/serialcomms/chapter.xml
==============================================================================
--- head/en_US.ISO8859-1/books/handbook/serialcomms/chapter.xml Wed May 7 16:22:52 2014 (r44785)
+++ head/en_US.ISO8859-1/books/handbook/serialcomms/chapter.xml Wed May 7 18:12:21 2014 (r44786)
@@ -758,171 +758,112 @@
</variablelist>
<sect2 xml:id="term-config">
- <title>Configuration</title>
+ <title>Terminal Configuration</title>
<para>This section describes how to configure a &os; system to
- enable a login session on a terminal. It assumes that the
- kernel is configured to support the serial port to which the
+ enable a login session on a serial terminal. It assumes that the
+ system recognizes the serial port to which the
terminal is connected and that the terminal is
- connected.</para>
+ connected with the correct cable.</para>
- <para>The <command>init</command> process is responsible for all
- process control and initialization at system startup. One of
- the tasks performed by <command>init</command> is to read
- <filename>/etc/ttys</filename> and start a
+ <para>In &os;, <command>init</command> reads
+ <filename>/etc/ttys</filename> and starts a
<command>getty</command> process on the available terminals.
The <command>getty</command> process is responsible for
reading a login name and starting the <command>login</command>
- program.</para>
-
- <para>To configure terminals for a &os; system, the following
- steps should be taken as <systemitem
- class="username">root</systemitem>:</para>
-
- <procedure>
- <step>
- <para>Add a line to <filename>/etc/ttys</filename> for the
- entry in <filename>/dev</filename> for the serial port if
- it is not already there.</para>
- </step>
-
- <step>
- <para>Specify that <command>/usr/libexec/getty</command>
- be run on the port, and specify the appropriate
- <replaceable>getty</replaceable> type from
- <filename>/etc/gettytab</filename>.</para>
- </step>
-
- <step>
- <para>Specify the default terminal type.</para>
- </step>
-
- <step>
- <para>Set the port to <quote>on.</quote></para>
- </step>
-
- <step>
- <para>Specify whether the port should be
- <quote>secure.</quote></para>
- </step>
-
- <step>
- <para>Force <command>init</command> to reread
- <filename>/etc/ttys</filename>.</para>
- </step>
- </procedure>
-
- <para>As an optional step, create a custom
- <replaceable>getty</replaceable> type for use in step 2 by
- making an entry in <filename>/etc/gettytab</filename>. For
- more information, refer to &man.gettytab.5; and
- &man.getty.8;.</para>
-
- <sect3 xml:id="term-etcttys">
- <title>Adding an Entry to
- <filename>/etc/ttys</filename></title>
-
- <para><filename>/etc/ttys</filename> lists all of the ports
- on the &os; system which allow logins. For example, the
- first virtual console, <filename>ttyv0</filename>, has an
- entry in this file, allowing logins on the console. This
- file also contains entries for the other virtual consoles,
- serial ports, and pseudo-ttys. For a hardwired terminal,
- list the serial port's <filename>/dev</filename> entry
- without the <literal>/dev</literal> part. For example,
- <filename>/dev/ttyv0</filename> would be listed as
- <literal>ttyv0</literal>.</para>
-
- <para>A default &os; install includes an
- <filename>/etc/ttys</filename> with support for the first
- four serial ports: <filename>ttyu0</filename> through
- <filename>ttyu3</filename>. When attaching a terminal to
- one of those ports, this file does not need to be
- edited.</para>
-
- <example xml:id="ex-etc-ttys">
- <title>Adding Terminal Entries to
- <filename>/etc/ttys</filename></title>
-
- <para>This example configures two terminals: a Wyse-50 and
- an old 286 IBM PC running
+ program. The ports on the &os; system which allow logins are
+ listed in <filename>/etc/ttys</filename>. For example, the
+ first virtual console, <filename>ttyv0</filename>, has an
+ entry in this file, allowing logins on the console. This
+ file also contains entries for the other virtual consoles,
+ serial ports, and pseudo-ttys. For a hardwired terminal,
+ the serial port's <filename>/dev</filename> entry is listed
+ without the <literal>/dev</literal> part. For example,
+ <filename>/dev/ttyv0</filename> is listed as
+ <literal>ttyv0</literal>.</para>
+
+ <para>The default
+ <filename>/etc/ttys</filename> configures support for the first
+ four serial ports, <filename>ttyu0</filename> through
+ <filename>ttyu3</filename>:</para>
+
+ <programlisting>ttyu0 "/usr/libexec/getty std.9600" dialup off secure
+ttyu1 "/usr/libexec/getty std.9600" dialup off secure
+ttyu2 "/usr/libexec/getty std.9600" dialup off secure
+ttyu3 "/usr/libexec/getty std.9600" dialup off secure</programlisting>
+
+ <para>When attaching a terminal to
+ one of those ports, modify the default entry to set the
+ required speed and terminal type, to turn the device
+ <literal>on</literal> and, if needed, to change the port's
+ <literal>secure</literal> setting. If the terminal is
+ connected to another port, add an entry for the port.</para>
+
+ <para><xref linkend="ex-etc-ttys"/> configures two
+ terminals in <filename>/etc/ttys</filename>. The first
+ entry configures a Wyse-50
+ connected to <filename>COM2</filename>. The second entry
+ configures an old computer running
<application>Procomm</application> terminal software
- emulating a VT-100 terminal. The Wyse is connected to the
- second serial port and the 286 to the sixth serial port on
- a multiport serial card. The corresponding entries in
- <filename>/etc/ttys</filename> would look like
- this:</para>
+ emulating a VT-100 terminal. The computer is connected
+ to the sixth serial port on
+ a multi-port serial card.</para>
+
+ <example xml:id="ex-etc-ttys">
+ <title>Configuring Terminal Entries</title>
<programlisting>ttyu1<co xml:id="co-ttys-line1col1"/> "/usr/libexec/getty std.38400"<co xml:id="co-ttys-line1col2"/> wy50<co xml:id="co-ttys-line1col3"/> on<co xml:id="co-ttys-line1col4"/> insecure<co xml:id="co-ttys-line1col5"/>
ttyu5 "/usr/libexec/getty std.19200" vt100 on insecure</programlisting>
<calloutlist>
<callout arearefs="co-ttys-line1col1">
- <para>The first field normally specifies the name of
- the terminal special file as it is found in
- <filename>/dev</filename>.</para>
+ <para>The first field specifies the device name of
+ the serial terminal.</para>
</callout>
<callout arearefs="co-ttys-line1col2">
- <para>The second field is the command to execute for
- this line, which is usually &man.getty.8;.
- <command>getty</command> initializes and opens the
- line, sets the speed, prompts for a user name, and
- then executes &man.login.1;.</para>
-
- <para>The <command>getty</command> program accepts one
- (optional) parameter on its command line, the
- <replaceable>getty</replaceable> type. A
- <replaceable>getty</replaceable> type configures
+ <para>The second field tells
+ <command>getty</command> to initialize and open the
+ line, set the line speed, prompt for a user name, and
+ then execute the <command>login</command> program. The optional
+ <firstterm>getty type</firstterm> configures
characteristics on the terminal line, like
- <acronym>bps</acronym> rate and parity.
- <command>getty</command> reads these characteristics
- from <filename>/etc/gettytab</filename>.</para>
-
- <para><filename>/etc/gettytab</filename> contains many
- entries for terminal lines, both old and new. In
- almost all cases, the entries that start with the
- text <literal>std</literal> will work for hardwired
+ <acronym>bps</acronym> rate and parity. The available
+ getty types are listed in
+ <filename>/etc/gettytab</filename>. In
+ almost all cases, the getty types that start with
+ <literal>std</literal> will work for hardwired
terminals as these entries ignore parity. There is
a <literal>std</literal> entry for each
- <acronym>bps</acronym> rate from 110 to 115200.
- &man.gettytab.5; provides more information.</para>
-
- <para>When setting the <replaceable>getty</replaceable>
- type in <filename>/etc/ttys</filename>, make sure
- that the communications settings on the terminal
- match.</para>
+ <acronym>bps</acronym> rate from 110 to 115200. Refer to
+ &man.gettytab.5; for more information.</para>
- <para>For this example, the Wyse-50 uses no parity and
- connects at 38400 bps. The 286 PC uses no
+ <para>When setting the getty
+ type, make sure to match
+ the communications settings used by the terminal. For
+ this example, the Wyse-50 uses no parity and
+ connects at 38400 bps. The computer uses no
parity and connects at 19200 bps.</para>
</callout>
<callout arearefs="co-ttys-line1col3">
- <para>The third field is the type of terminal usually
- connected to that terminal line. For dial-up ports,
+ <para>The third field is the type of terminal. For dial-up ports,
<literal>unknown</literal> or
<literal>dialup</literal> is typically used since
users may dial up with practically any type of
terminal or software. Since the terminal type does
not change for hardwired terminals, a real terminal
- type from &man.termcap.5; can be used in this
- field.</para>
-
- <para>For this example, the Wyse-50 uses the real
- terminal type while the 286 PC running
- <application>Procomm</application> will be set to
- emulate at VT-100. </para>
+ type from <filename>/etc/termcap</filename> can be specified.
+ For this example, the Wyse-50 uses the real
+ terminal type while the computer running
+ <application>Procomm</application> is set to
+ emulate a VT-100.</para>
</callout>
<callout arearefs="co-ttys-line1col4">
<para>The fourth field specifies if the port should be
- enabled. If set to <literal>on</literal>, the
- <command>init</command> process will start the program
- in the second field, <command>getty</command>. If
- this field is set to <literal>off</literal>, there
- will be no <command>getty</command>, and hence no
- logins on the port.</para>
+ enabled. To enable logins on this port, this
+ field must be set to <literal>on</literal>.</para>
</callout>
<callout arearefs="co-ttys-line1col5">
@@ -930,27 +871,18 @@ ttyu5 "/usr/libexec/getty std.19200"
port is secure. Marking a port as
<literal>secure</literal> means that it is trusted
enough to allow <systemitem
- class="username">root</systemitem>, or any account
- with a <acronym>UID</acronym> of 0, to login from that
+ class="username">root</systemitem> to login from that
port. Insecure ports do not allow <systemitem
class="username">root</systemitem> logins. On an
insecure port, users must login from unprivileged
- accounts and then use &man.su.1; or a similar
- mechanism to gain superuser privileges.</para>
-
- <para>It is highly recommended to use
- <literal>insecure</literal>, even for terminals that
- are behind locked doors. It is quite easy to login
- and use <command>su</command> when superuser
- privileges are needed.</para>
+ accounts and then use <command>su</command> or a similar
+ mechanism to gain superuser privileges, as described
+ in <xref linkend="users-superuser"/>. For security reasons,
+ it is recommended to change this setting to
+ <literal>insecure</literal>.</para>
</callout>
</calloutlist>
</example>
- </sect3>
-
- <sect3 xml:id="term-hup">
- <title>Force <command>init</command> to Reread
- <filename>/etc/ttys</filename></title>
<para>After making any changes to
<filename>/etc/ttys</filename>, send a SIGHUP (hangup)
@@ -959,18 +891,15 @@ ttyu5 "/usr/libexec/getty std.19200"
<screen>&prompt.root; <userinput>kill -HUP 1</userinput></screen>
- <note>
- <para><command>init</command> is always the first process
- run on a system, therefore it will always have a process
- ID of 1.</para>
- </note>
+ <para>Since <command>init</command> is always the first process
+ run on a system, it always has a process
+ <acronym>ID</acronym> of <literal>1</literal>.</para>
<para>If everything is set up correctly, all cables are in
- place, and the terminals are powered up, then a
- <command>getty</command> process should be running on each
+ place, and the terminals are powered up, a
+ <command>getty</command> process should now be running on each
terminal and login prompts should be available on each
terminal.</para>
- </sect3>
</sect2>
<sect2 xml:id="term-debug">
@@ -996,20 +925,16 @@ ttyu5 "/usr/libexec/getty std.19200"
controls are turned up. If it is a printing terminal, make
sure paper and ink are in good supply.</para>
- <para>Make sure that a <command>getty</command> process is
- running and serving the terminal. For example, to get a list
- of running <command>getty</command> processes with
- <command>ps</command>, type:</para>
-
- <screen>&prompt.root; <userinput>ps -axww|grep getty</userinput></screen>
-
- <para>There should be an entry for the terminal. For example,
- the following display shows that a <command>getty</command> is
+ <para>Use <command>ps</command> to make sure that a
+ <command>getty</command> process is
+ running and serving the terminal. For example,
+ the following listing shows that a <command>getty</command> is
running on the second serial port, <filename>ttyu1</filename>,
and is using the <literal>std.38400</literal> entry in
<filename>/etc/gettytab</filename>:</para>
- <screen>22189 d1 Is+ 0:00.03 /usr/libexec/getty std.38400 ttyu1</screen>
+ <screen>&prompt.root; <userinput>ps -axww|grep ttyu</userinput>
+22189 d1 Is+ 0:00.03 /usr/libexec/getty std.38400 ttyu1</screen>
<para>If no <command>getty</command> process is running, make
sure the port is enabled in <filename>/etc/ttys</filename>.
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