Finish editorial review of Terminals.
Sponsored by: iXsystems
This commit is contained in:
Dru Lavigne
parent
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Notes:
svn2git
2020-12-08 03:00:23 +00:00
svn path=/head/; revision=44786
1 changed files with 85 additions and 160 deletions
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@ -758,171 +758,112 @@
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</variablelist>
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<sect2 xml:id="term-config">
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<title>Configuration</title>
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<title>Terminal Configuration</title>
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<para>This section describes how to configure a &os; system to
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enable a login session on a terminal. It assumes that the
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kernel is configured to support the serial port to which the
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enable a login session on a serial terminal. It assumes that the
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system recognizes the serial port to which the
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terminal is connected and that the terminal is
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connected.</para>
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connected with the correct cable.</para>
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<para>The <command>init</command> process is responsible for all
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process control and initialization at system startup. One of
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the tasks performed by <command>init</command> is to read
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<filename>/etc/ttys</filename> and start a
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<para>In &os;, <command>init</command> reads
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<filename>/etc/ttys</filename> and starts a
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<command>getty</command> process on the available terminals.
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The <command>getty</command> process is responsible for
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reading a login name and starting the <command>login</command>
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program.</para>
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program. The ports on the &os; system which allow logins are
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listed in <filename>/etc/ttys</filename>. For example, the
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first virtual console, <filename>ttyv0</filename>, has an
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entry in this file, allowing logins on the console. This
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file also contains entries for the other virtual consoles,
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serial ports, and pseudo-ttys. For a hardwired terminal,
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the serial port's <filename>/dev</filename> entry is listed
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without the <literal>/dev</literal> part. For example,
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<filename>/dev/ttyv0</filename> is listed as
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<literal>ttyv0</literal>.</para>
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<para>To configure terminals for a &os; system, the following
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steps should be taken as <systemitem
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class="username">root</systemitem>:</para>
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<para>The default
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<filename>/etc/ttys</filename> configures support for the first
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four serial ports, <filename>ttyu0</filename> through
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<filename>ttyu3</filename>:</para>
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<procedure>
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<step>
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<para>Add a line to <filename>/etc/ttys</filename> for the
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entry in <filename>/dev</filename> for the serial port if
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it is not already there.</para>
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</step>
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<programlisting>ttyu0 "/usr/libexec/getty std.9600" dialup off secure
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ttyu1 "/usr/libexec/getty std.9600" dialup off secure
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ttyu2 "/usr/libexec/getty std.9600" dialup off secure
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ttyu3 "/usr/libexec/getty std.9600" dialup off secure</programlisting>
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<step>
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<para>Specify that <command>/usr/libexec/getty</command>
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be run on the port, and specify the appropriate
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<replaceable>getty</replaceable> type from
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<filename>/etc/gettytab</filename>.</para>
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</step>
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<para>When attaching a terminal to
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one of those ports, modify the default entry to set the
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required speed and terminal type, to turn the device
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<literal>on</literal> and, if needed, to change the port's
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<literal>secure</literal> setting. If the terminal is
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connected to another port, add an entry for the port.</para>
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<step>
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<para>Specify the default terminal type.</para>
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</step>
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<step>
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<para>Set the port to <quote>on.</quote></para>
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</step>
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<step>
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<para>Specify whether the port should be
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<quote>secure.</quote></para>
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</step>
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<step>
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<para>Force <command>init</command> to reread
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<filename>/etc/ttys</filename>.</para>
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</step>
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</procedure>
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<para>As an optional step, create a custom
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<replaceable>getty</replaceable> type for use in step 2 by
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making an entry in <filename>/etc/gettytab</filename>. For
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more information, refer to &man.gettytab.5; and
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&man.getty.8;.</para>
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<sect3 xml:id="term-etcttys">
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<title>Adding an Entry to
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<filename>/etc/ttys</filename></title>
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<para><filename>/etc/ttys</filename> lists all of the ports
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on the &os; system which allow logins. For example, the
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first virtual console, <filename>ttyv0</filename>, has an
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entry in this file, allowing logins on the console. This
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file also contains entries for the other virtual consoles,
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serial ports, and pseudo-ttys. For a hardwired terminal,
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list the serial port's <filename>/dev</filename> entry
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without the <literal>/dev</literal> part. For example,
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<filename>/dev/ttyv0</filename> would be listed as
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<literal>ttyv0</literal>.</para>
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<para>A default &os; install includes an
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<filename>/etc/ttys</filename> with support for the first
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four serial ports: <filename>ttyu0</filename> through
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<filename>ttyu3</filename>. When attaching a terminal to
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one of those ports, this file does not need to be
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edited.</para>
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<example xml:id="ex-etc-ttys">
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<title>Adding Terminal Entries to
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<filename>/etc/ttys</filename></title>
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<para>This example configures two terminals: a Wyse-50 and
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an old 286 IBM PC running
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<para><xref linkend="ex-etc-ttys"/> configures two
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terminals in <filename>/etc/ttys</filename>. The first
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entry configures a Wyse-50
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connected to <filename>COM2</filename>. The second entry
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configures an old computer running
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<application>Procomm</application> terminal software
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emulating a VT-100 terminal. The Wyse is connected to the
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second serial port and the 286 to the sixth serial port on
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a multiport serial card. The corresponding entries in
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<filename>/etc/ttys</filename> would look like
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this:</para>
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emulating a VT-100 terminal. The computer is connected
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to the sixth serial port on
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a multi-port serial card.</para>
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<example xml:id="ex-etc-ttys">
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<title>Configuring Terminal Entries</title>
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<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"/>
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ttyu5 "/usr/libexec/getty std.19200" vt100 on insecure</programlisting>
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<calloutlist>
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<callout arearefs="co-ttys-line1col1">
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<para>The first field normally specifies the name of
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the terminal special file as it is found in
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<filename>/dev</filename>.</para>
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<para>The first field specifies the device name of
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the serial terminal.</para>
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</callout>
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<callout arearefs="co-ttys-line1col2">
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<para>The second field is the command to execute for
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this line, which is usually &man.getty.8;.
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<command>getty</command> initializes and opens the
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line, sets the speed, prompts for a user name, and
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then executes &man.login.1;.</para>
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<para>The <command>getty</command> program accepts one
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(optional) parameter on its command line, the
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<replaceable>getty</replaceable> type. A
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<replaceable>getty</replaceable> type configures
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<para>The second field tells
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<command>getty</command> to initialize and open the
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line, set the line speed, prompt for a user name, and
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then execute the <command>login</command> program. The optional
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<firstterm>getty type</firstterm> configures
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characteristics on the terminal line, like
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<acronym>bps</acronym> rate and parity.
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<command>getty</command> reads these characteristics
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from <filename>/etc/gettytab</filename>.</para>
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<para><filename>/etc/gettytab</filename> contains many
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entries for terminal lines, both old and new. In
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almost all cases, the entries that start with the
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text <literal>std</literal> will work for hardwired
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<acronym>bps</acronym> rate and parity. The available
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getty types are listed in
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<filename>/etc/gettytab</filename>. In
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almost all cases, the getty types that start with
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<literal>std</literal> will work for hardwired
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terminals as these entries ignore parity. There is
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a <literal>std</literal> entry for each
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<acronym>bps</acronym> rate from 110 to 115200.
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&man.gettytab.5; provides more information.</para>
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<acronym>bps</acronym> rate from 110 to 115200. Refer to
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&man.gettytab.5; for more information.</para>
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<para>When setting the <replaceable>getty</replaceable>
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type in <filename>/etc/ttys</filename>, make sure
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that the communications settings on the terminal
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match.</para>
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<para>For this example, the Wyse-50 uses no parity and
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connects at 38400 bps. The 286 PC uses no
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<para>When setting the getty
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type, make sure to match
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the communications settings used by the terminal. For
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this example, the Wyse-50 uses no parity and
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connects at 38400 bps. The computer uses no
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parity and connects at 19200 bps.</para>
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</callout>
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<callout arearefs="co-ttys-line1col3">
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<para>The third field is the type of terminal usually
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connected to that terminal line. For dial-up ports,
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<para>The third field is the type of terminal. For dial-up ports,
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<literal>unknown</literal> or
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<literal>dialup</literal> is typically used since
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users may dial up with practically any type of
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terminal or software. Since the terminal type does
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not change for hardwired terminals, a real terminal
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type from &man.termcap.5; can be used in this
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field.</para>
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<para>For this example, the Wyse-50 uses the real
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terminal type while the 286 PC running
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<application>Procomm</application> will be set to
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emulate at VT-100. </para>
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type from <filename>/etc/termcap</filename> can be specified.
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For this example, the Wyse-50 uses the real
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terminal type while the computer running
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<application>Procomm</application> is set to
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emulate a VT-100.</para>
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</callout>
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<callout arearefs="co-ttys-line1col4">
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<para>The fourth field specifies if the port should be
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enabled. If set to <literal>on</literal>, the
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<command>init</command> process will start the program
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in the second field, <command>getty</command>. If
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this field is set to <literal>off</literal>, there
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will be no <command>getty</command>, and hence no
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logins on the port.</para>
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enabled. To enable logins on this port, this
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field must be set to <literal>on</literal>.</para>
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</callout>
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<callout arearefs="co-ttys-line1col5">
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@ -930,27 +871,18 @@ ttyu5 "/usr/libexec/getty std.19200" vt100 on insecure</programlisting>
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port is secure. Marking a port as
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<literal>secure</literal> means that it is trusted
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enough to allow <systemitem
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class="username">root</systemitem>, or any account
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with a <acronym>UID</acronym> of 0, to login from that
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class="username">root</systemitem> to login from that
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port. Insecure ports do not allow <systemitem
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class="username">root</systemitem> logins. On an
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insecure port, users must login from unprivileged
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accounts and then use &man.su.1; or a similar
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mechanism to gain superuser privileges.</para>
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<para>It is highly recommended to use
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<literal>insecure</literal>, even for terminals that
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are behind locked doors. It is quite easy to login
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and use <command>su</command> when superuser
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privileges are needed.</para>
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accounts and then use <command>su</command> or a similar
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mechanism to gain superuser privileges, as described
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in <xref linkend="users-superuser"/>. For security reasons,
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it is recommended to change this setting to
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<literal>insecure</literal>.</para>
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</callout>
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</calloutlist>
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</example>
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</sect3>
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<sect3 xml:id="term-hup">
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<title>Force <command>init</command> to Reread
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<filename>/etc/ttys</filename></title>
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<para>After making any changes to
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<filename>/etc/ttys</filename>, send a SIGHUP (hangup)
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@ -959,18 +891,15 @@ ttyu5 "/usr/libexec/getty std.19200" vt100 on insecure</programlisting>
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<screen>&prompt.root; <userinput>kill -HUP 1</userinput></screen>
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<note>
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<para><command>init</command> is always the first process
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run on a system, therefore it will always have a process
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ID of 1.</para>
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</note>
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<para>Since <command>init</command> is always the first process
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run on a system, it always has a process
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<acronym>ID</acronym> of <literal>1</literal>.</para>
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<para>If everything is set up correctly, all cables are in
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place, and the terminals are powered up, then a
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<command>getty</command> process should be running on each
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place, and the terminals are powered up, a
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<command>getty</command> process should now be running on each
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terminal and login prompts should be available on each
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terminal.</para>
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</sect3>
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</sect2>
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<sect2 xml:id="term-debug">
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@ -996,20 +925,16 @@ ttyu5 "/usr/libexec/getty std.19200" vt100 on insecure</programlisting>
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controls are turned up. If it is a printing terminal, make
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sure paper and ink are in good supply.</para>
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<para>Make sure that a <command>getty</command> process is
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running and serving the terminal. For example, to get a list
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of running <command>getty</command> processes with
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<command>ps</command>, type:</para>
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<screen>&prompt.root; <userinput>ps -axww|grep getty</userinput></screen>
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<para>There should be an entry for the terminal. For example,
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the following display shows that a <command>getty</command> is
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<para>Use <command>ps</command> to make sure that a
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<command>getty</command> process is
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running and serving the terminal. For example,
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the following listing shows that a <command>getty</command> is
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running on the second serial port, <filename>ttyu1</filename>,
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and is using the <literal>std.38400</literal> entry in
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<filename>/etc/gettytab</filename>:</para>
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<screen>22189 d1 Is+ 0:00.03 /usr/libexec/getty std.38400 ttyu1</screen>
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<screen>&prompt.root; <userinput>ps -axww|grep ttyu</userinput>
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22189 d1 Is+ 0:00.03 /usr/libexec/getty std.38400 ttyu1</screen>
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<para>If no <command>getty</command> process is running, make
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sure the port is enabled in <filename>/etc/ttys</filename>.
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