Commit c2ffd5da authored by Mauro Carvalho Chehab's avatar Mauro Carvalho Chehab
Browse files

Documentation/serial-console.txt: convert it to ReST markup 



- Fix identation for the document title;
- use monotonic fonts for paths;
- use quote blocks where needed;
- adjust spaces to properly format paragraphs;
- use :menuselection: for the menu item;
- add it to the user book.

Signed-off-by: default avatarMauro Carvalho Chehab <mchehab@s-opensource.com>
parent 5902981b

Documentation/serial-console.txt

+35 −31
Original line number Diff line number Diff line 
Linux Serial Console

====================



To use a serial port as console you need to compile the support into your

kernel - by default it is not compiled in. For PC style serial ports

it's the config option next to "Standard/generic (dumb) serial support".

it's the config option next to menu option:



:menuselection:`Character devices --> Serial drivers --> 8250/16550 and compatible serial support --> Console on 8250/16550 and compatible serial port`



You must compile serial support into the kernel and not as a module.



It is possible to specify multiple devices for console output. You can

define a new kernel command line option to select which device(s) to

use for console output.



The format of this option is:

The format of this option is::



	console=device,options
@@ -28,11 +32,11 @@ The format of this option is: 


You can specify multiple console= options on the kernel command line.

Output will appear on all of them. The last device will be used when

you open /dev/console. So, for example:

you open ``/dev/console``. So, for example::



	console=ttyS1,9600 console=tty0



defines that opening /dev/console will get you the current foreground

defines that opening ``/dev/console`` will get you the current foreground

virtual console, and kernel messages will appear on both the VGA

console and the 2nd serial port (ttyS1 or COM2) at 9600 baud.
@@ -44,17 +48,17 @@ first looks for a VGA card and then for a serial port. So if you don't 
have a VGA card in your system the first serial port will automatically

become the console.



You will need to create a new device to use /dev/console. The official

/dev/console is now character device 5,1.

You will need to create a new device to use ``/dev/console``. The official

``/dev/console`` is now character device 5,1.



(You can also use a network device as a console.  See

Documentation/networking/netconsole.txt for information on that.)

``Documentation/networking/netconsole.txt`` for information on that.)



Here's an example that will use /dev/ttyS1 (COM2) as the console.

Here's an example that will use ``/dev/ttyS1`` (COM2) as the console.

Replace the sample values as needed.



1. Create /dev/console (real console) and /dev/tty0 (master virtual

   console):

1. Create ``/dev/console`` (real console) and ``/dev/tty0`` (master virtual

   console)::



     cd /dev

     rm -f console tty0
@@ -63,42 +67,42 @@ Replace the sample values as needed. 


2. LILO can also take input from a serial device. This is a very

   useful option. To tell LILO to use the serial port:

   In lilo.conf (global section): 

   In lilo.conf (global section)::



     serial  = 1,9600n8 (ttyS1, 9600 bd, no parity, 8 bits)



3. Adjust to kernel flags for the new kernel,

   again in lilo.conf (kernel section)

   again in lilo.conf (kernel section)::



     append = "console=ttyS1,9600"



4. Make sure a getty runs on the serial port so that you can login to

   it once the system is done booting. This is done by adding a line

   like this to /etc/inittab (exact syntax depends on your getty):

   like this to ``/etc/inittab`` (exact syntax depends on your getty)::



     S1:23:respawn:/sbin/getty -L ttyS1 9600 vt100



5. Init and /etc/ioctl.save

5. Init and ``/etc/ioctl.save``



   Sysvinit remembers its stty settings in a file in /etc, called

   `/etc/ioctl.save'. REMOVE THIS FILE before using the serial

   Sysvinit remembers its stty settings in a file in ``/etc``, called

   ``/etc/ioctl.save``. REMOVE THIS FILE before using the serial

   console for the first time, because otherwise init will probably

   set the baudrate to 38400 (baudrate of the virtual console).



6. /dev/console and X

6. ``/dev/console`` and X

   Programs that want to do something with the virtual console usually

   open /dev/console. If you have created the new /dev/console device,

   open ``/dev/console``. If you have created the new ``/dev/console`` device,

   and your console is NOT the virtual console some programs will fail.

   Those are programs that want to access the VT interface, and use

   /dev/console instead of /dev/tty0. Some of those programs are:

   ``/dev/console instead of /dev/tty0``. Some of those programs are::



     Xfree86, svgalib, gpm, SVGATextMode



   It should be fixed in modern versions of these programs though.



   Note that if you boot without a console= option (or with

   console=/dev/tty0), /dev/console is the same as /dev/tty0. In that

   case everything will still work.

   Note that if you boot without a ``console=`` option (or with

   ``console=/dev/tty0``), ``/dev/console`` is the same as ``/dev/tty0``.

   In that case everything will still work.



7. Thanks