virtual console -- Technical Information

COHERENT system of multiple virtual consoles

The ``virtual  consoles'' feature  of COHERENT  allows you to  run multiple
sessions from  the system console.  You can switch  between sessions on the
console screen using the appropriate keystrokes.  If your computer has both
monochrome  and color  video adapters  and monitors,  you can  run multiple
sessions on both screens simultaneously.

For  this feature  to be  available,   your system  must be  configured for
virtual   consoles.    Normally,   this   configuration  is   done   during
installation.  In  addition, virtual console  sessions must be  enabled for
logins prior to use.  Virtual terminals are most useful when your system is
running in multiuser mode.

COHERENT allows up to ten sessions  at a given time.  All you need to do to
access multiple sessions is to hold down the <Ctrl> key on the system
keyboard and  press the  digit on the  numeric keypad corresponding  to the
desired active  session number.  Simultaneously  pressing keys <Ctrl>
and <.>  (located on the  numeric keypad) will  take you to  the next
open virtual  terminal session.  Another means of  switching sessions is to
hold down the  <Alt> key and press one of  the ``function keys''.  By
default,  function  key <F10>  takes  you to  the  next open  virtual
terminal  session,  <F11>  takes you  to  the  previous open  virtual
terminal  session,   and  <F12>  toggles  between   the  current  and
previously selected sessions.

Technical Features

It  is  not  essential to  know  the  following  in  order to  use  virtual
terminals.   We provide  this information  for advanced  users, as  well as
persons wishing to customize their  systems in ways not available under the
default scheme used by the COHERENT installation procedure.

Different  sessions  are  accessed  by  using  different  device  names  in
directory /dev.  Like any character  special device, each  virtual terminal
screen has a  major and minor number associated with  it.  The major number
for all virtual  terminal screens is 2.  The device  with minor number 0 is
initially the console device -- this is where output appears during startup
and  at  other times  when  the  system is  in  single-user mode.   Virtual
terminals are assigned successive minor numbers.  When there are both color
and monochrome display adapters on the system, the color sessions are given
the  lower minor  numbers.  For  example, in a  system configured  for four
color and  four monochrome sessions,  logical devices might  be numbered as
follows:

crwxr-xr-x 1 root   root     2   0 Mon Jun 15 14:51 /dev/console
crwxr-xr-x 1 root   root     2   1 Mon Jun 15 14:51 /dev/vcolor0
crwxr-xr-x 1 root   root     2   2 Mon Jun 15 14:51 /dev/vcolor1
crwxr-xr-x 1 root   root     2   3 Mon Jun 15 14:51 /dev/vcolor2
crwxr-xr-x 1 root   root     2   4 Mon Jun 15 14:51 /dev/vcolor3
crwxr-xr-x 1 root   root     2   5 Mon Jun 15 14:50 /dev/vmono0
crwxr-xr-x 1 root   root     2   6 Mon Jun 15 14:50 /dev/vmono1
crwxr-xr-x 1 root   root     2   7 Mon Jun 15 14:50 /dev/vmono2
crwxr-xr-x 1 root   root     2   8 Mon Jun 15 14:50 /dev/vmono3

Alternatively,  using  physical  device  numbering,  successive  color-only
sessions can  be accessed  by using  minor numbers 64-79,  while successive
monochrome-only  sessions  are  selected  with  minor numbers  80-95.   The
configuration of  four color plus four  monochrome sessions described above
could also be represented as:

crwxr-xr-x 1 root   root     2  64 Mon Jun 15 14:51 /dev/color0
crwxr-xr-x 1 root   root     2  65 Mon Jun 15 14:51 /dev/color1
crwxr-xr-x 1 root   root     2  66 Mon Jun 15 14:51 /dev/color2
crwxr-xr-x 1 root   root     2  67 Mon Jun 15 14:51 /dev/color3
crwxr-xr-x 1 root   root     2  80 Mon Jun 15 14:50 /dev/mono0
crwxr-xr-x 1 root   root     2  81 Mon Jun 15 14:50 /dev/mono1
crwxr-xr-x 1 root   root     2  82 Mon Jun 15 14:50 /dev/mono2
crwxr-xr-x 1 root   root     2  83 Mon Jun 15 14:50 /dev/mono3

The following  diagram summarizes bit  assignments in the  virtual terminal
minor number:

    7654  3210
     |      1=physical device, 0=logical device
      ||        00=color, 01=mono, 1x=reserved
          ||||  terminal's index number

The  system  initially  defaults  to  a  maximum of  four  color  and  four
monochrome sessions.   This may be altered  by patching character variables
VTVGA and VTMONO. For example, to  allow for six color and three monochrome
sessions, enter the following command while running as root (note that this
will not take effect until after the system has been rebooted):

    /conf/patch -v /coherent VTVGA=6:c VTMONO=3:c

Running  multiple  sessions on  different  virtual  consoles requires  that
logins be enabled for each of the virtual consoles.  Each session must have
a corresponding  entry in  file /etc/ttys.  For example, a  system allowing
four color and four monochrome  sessions would have entries in /etc/ttys as
follows:

    0lPconsole
    1lPcolor0
    1lPcolor1
    1lPcolor2
    1lPcolor3
    1lPmono0
    1lPmono1
    1lPmono2
    1lPmono3

Device  /dev/console  must  not be  enabled  when  using virtual  consoles!
Additional lines  would be present if logins are  enabled for other devices
such as serial  ports.  Commands enable and disable may  be used, as usual,
to allow or disallow logins on individual virtual consoles.

When virtual  terminals are enabled, kernel output,  such as messages about
user traps  or system panics,  goes to the currently  active session (i.e.,
the session with the cursor showing).

Altering Virtual Consoles

To add, delete,  or alter the configuration of virtual  consoles, log in as
the superuser root and type the following commands:

    cd /etc/conf
    console/mkdev
    bin/idmkcoh -o /kernel_name

where kernel_name  is what you wish  to name the newly  built kernel.  When
you  reboot,   invoke  kernel_name  in  the  usual   manner  and  your  new
configuration will have been implemented.

See Also

Administering COHERENT,
console,
device drivers,
enable,
kb.h

Notes

Some confusion can  arise when you attempt to install  COHERENT to use both
color and monochrome consoles.

At installation time,  you are asked if you want  to install both color and
monochrome  screens.   If you  reply  ``yes,'' you  must  select only  four
multiscreens for  each.  Otherwise, you  will find it  difficult to address
virtual consoles  on both consoles:  COHERENT uses the  lower function keys
for virtual consoles on the color  monitor, and the upper function keys for
those on the monochrome monitor.

If you  have requested  two consoles, COHERENT  uses the color  terminal by
default.  If  you really have  only a monochrome monitor  plugged into your
system,  you  must  invoke  the  appropriate  monochrome  virtual  console;
otherwise, you will nothing on your monitor.

© 2012 by Stephen A. Ness