Ubuntu Manpage: syscons, sc — the console driver

Provided by: freebsd-manpages_12.2-1_all

NAME

       syscons, sc — the console driver

SYNOPSIS

       options MAXCONS=N
       options SC_ALT_MOUSE_IMAGE
       options SC_CUT_SEPCHARS=_characters_
       options SC_CUT_SPACES2TABS
       options SC_DISABLE_KDBKEY
       options SC_DISABLE_REBOOT
       options SC_HISTORY_SIZE=N
       options SC_MOUSE_CHAR=C
       options SC_NO_CUTPASTE
       options SC_NO_FONT_LOADING
       options SC_NO_HISTORY
       options SC_NO_PALETTE_LOADING
       options SC_NO_SUSPEND_VTYSWITCH
       options SC_NO_SYSMOUSE
       options SC_PIXEL_MODE
       options SC_TWOBUTTON_MOUSE
       options SC_NORM_ATTR=_attribute_
       options SC_NORM_REV_ATTR=_attribute_
       options SC_KERNEL_CONS_ATTR=_attribute_
       options SC_KERNEL_CONS_ATTRS=_attributes_
       options SC_KERNEL_CONS_REV_ATTR=_attribute_
       options SC_DFLT_FONT
       makeoptions SC_DFLT_FONT=_font_name_
       device sc

       In /boot/device.hints:
       hint.sc.0.at="isa"
       hint.sc.0.vesa_mode=0x103

       In /boot/loader.conf:
       kern.vty=sc

DESCRIPTION

The syscons driver provides multiple virtual terminals. It resembles the SCO color console driver.

The syscons driver is implemented on top of the keyboard driver (atkbd(4)) and the video card driver
(vga(4)) and so requires both of them to be configured in the system.

There can be only one syscons device defined in the system.

Virtual Terminals
The syscons driver provides multiple virtual terminals which appear as if they were separate terminals.
One virtual terminal is considered current and exclusively occupies the screen and the keyboard; the
other virtual terminals are placed in the background.

In order to use virtual terminals, they must be individually marked ``on'' in /etc/ttys so that getty(8)
will recognize them to be active and run login(1) to let the user log in to the system. By default, only
the first eight virtual terminals are activated in /etc/ttys.

You press the Alt key and a switch key to switch between virtual terminals. The following table
summarizes the correspondence between the switch key and the virtual terminal.

Alt-F1 ttyv0 Alt-F7 ttyv6 Shift-Alt-F1 ttyva
Alt-F2 ttyv1 Alt-F8 ttyv7 Shift-Alt-F2 ttyvb
Alt-F3 ttyv2 Alt-F9 ttyv8 Shift-Alt-F3 ttyvc
Alt-F4 ttyv3 Alt-F10 ttyv9 Shift-Alt-F4 ttyvd
Alt-F5 ttyv4 Alt-F11 ttyva Shift-Alt-F5 ttyve
Alt-F6 ttyv5 Alt-F12 ttyvb Shift-Alt-F6 ttyvf

You can also use the ``nscr'' key (usually the PrintScreen key on the AT Enhanced keyboard) to cycle
available virtual terminals.

The default number of available virtual terminals is 16. This can be changed with the kernel
configuration option MAXCONS (see below).

Note that the X server usually requires a virtual terminal for display purposes, so at least one terminal
must be left unused by getty(8) so that it can be used by the X server.

Key Definitions and Function Key Strings
The syscons driver, in conjunction with the keyboard driver, allows the user to change key definitions
and function key strings. The kbdcontrol(1) command will load a key definition file (known as ``keymap''
file), dump the current keymap, and assign a string to a function key. See keyboard(4) and kbdmap(5) for
the keymap file.

You may want to set the keymap variable in /etc/rc.conf.local to the desired keymap file so that it will
be automatically loaded when the system starts up.

Software Font
For most modern video cards, e.g., VGA, the syscons driver and the video card driver allow the user to
change the font used on the screen. The vidcontrol(1) command can be used to load a font file from
/usr/share/syscons/fonts.

The font comes in various sizes: 8x8, 8x14 and 8x16. The 8x16 font is typically used for the VGA card in
the 80-column-by-25-line mode. Other video modes may require different font sizes. It is better to
always load all three sizes of the same font.

You may set font8x8, font8x14 and font8x16 variables in /etc/rc.conf to the desired font files so that
they will be automatically loaded when the system starts up.

Optionally you can specify a particular font file as the default. See the SC_DFLT_FONT option below.

Screen Map
If your video card does not support software fonts, you may still be able to achieve a similar effect by
re-mapping the font built into your video card. Use vidcontrol(1) to load a screen map file which
defines the mapping between character codes.

Mouse Support and Copy-and-Paste
You can use your mouse to copy text on the screen and paste it as if it was typed by hand. You must be
running the mouse daemon moused(8) and enable the mouse cursor in the virtual terminal via vidcontrol(1).

Pressing mouse button 1 (usually the left button) will start selection. Releasing button 1 will end the
selection process. The selected text will be marked by inverting foreground and background colors. You
can press button 3 (usually the right button) to extend the selected region. The selected text is placed
in the copy buffer and can be pasted at the cursor position by pressing button 2 (usually the middle
button) as many times as you like.

If your mouse has only two buttons, you may want to use the SC_TWOBUTTON_MOUSE option below to make the
right button to paste the text. Alternatively you can make the mouse daemon emulate the middle button.
See the man page for moused(8) for more details.

Back Scrolling
The syscons driver allows the user to browse the output which has ``scrolled off'' the top of the screen.

Press the ``slock'' key (usually ScrllLock / Scroll Lock or Pause on many keyboards) and the terminal is
in the ``scrollback'' mode. It is indicated by the Scroll Lock LED. Use the arrow keys, the Page
Up/Down keys and the Home/End keys to scroll buffered terminal output. Press the ``slock'' key again to
get back to the normal terminal mode.

The size of the scrollback buffer can be set by the SC_HISTORY_SIZE option described below.

Screen Saver
The syscons driver can be made to put up the screen saver if the current virtual terminal is idle, that
is, the user is not typing on the keyboard nor moving the mouse. See splash(4) and vidcontrol(1) for
more details.

DRIVER CONFIGURATION

Kernel Configuration Options
The following kernel configuration options control the syscons driver.

MAXCONS=N
This option sets the number of virtual terminals to N. The default value is 16.

SC_ALT_MOUSE_IMAGE
This option selects the alternative way of displaying the mouse cursor in the virtual terminal.
It may be expensive for some video cards to draw the arrow-shaped cursor, and you may want to try
this option. However, the appearance of the alternative mouse cursor may not be very appealing.
Note that if you use the SC_NO_FONT_LOADING option then you must also use this option if you wish
to be able to use the mouse.

SC_CUT_SEPCHARS=_characters_
This options specifies characters that will be looked for when the driver searches for words
boundaries when doing cut operation. By default, its value is "\x20" — a space character.

SC_CUT_SPACES2TABS
This options instructs the driver to convert leading spaces into tabs when copying data into cut
buffer. This might be useful to preserve indentation when copying tab-indented text.

SC_DISABLE_KDBKEY
This option disables the ``debug'' key combination (by default, it is Alt-Esc, or
Ctl-PrintScreen). It will prevent users from entering the kernel debugger (KDB) by pressing the
key combination. KDB will still be invoked when the kernel panics or hits a break point if it is
included in the kernel. If this option is not defined, this behavior may be controlled at runtime
by the sysctl(8) variable hw.syscons.kbd_debug.

SC_DISABLE_REBOOT
This option disables the ``reboot'' key (by default, it is Ctl-Alt-Del), so that the casual user
may not accidentally reboot the system. If this option is not defined, this behavior may be
controlled at runtime by the sysctl(8) variable hw.syscons.kbd_reboot.

SC_HISTORY_SIZE=N
Sets the size of back scroll buffer to N lines. The default value is 100.

SC_MOUSE_CHAR=C
Unless the SC_ALT_MOUSE_IMAGE option above is specified, the syscons driver reserves four
consecutive character codes in order to display the mouse cursor in the virtual terminals in some
systems. This option specifies the first character code to C to be used for this purpose. The
default value is 0xd0. A good candidate is 0x03.

SC_PIXEL_MODE
Adds support for pixel (raster) mode console. This mode is useful on some laptop computers, but
less so on most other systems, and it adds substantial amount of code to syscons. If this option
is NOT defined, you can reduce the kernel size a lot. See the VESAMODE flag below.

SC_TWOBUTTON_MOUSE
If you have a two button mouse, you may want to add this option to use the right button of the
mouse to paste text. See “Mouse Support and Copy-and-Paste” above.

SC_NORM_ATTR=_attribute_

SC_NORM_REV_ATTR=_attribute_

SC_KERNEL_CONS_ATTR=_attribute_

SC_KERNEL_CONS_ATTRS=_attributes_

SC_KERNEL_CONS_REV_ATTR=_attribute_
These options will set the default colors. Available colors are defined in
<machine/pc/display.h>. See “EXAMPLES” below. SC_KERNEL_CONS_ATTRS is a character string giving
a sequence of attributes in binary format. The sequence will be repeated up to the number of
CPUs. Beware that the string must not be null, since the kernel divides by its length.

SC_DFLT_FONT
This option will specify the default font. Available fonts are: iso, iso2, koi8-r, koi8-u, cp437,
cp850, cp865, cp866 and cp866u. 16-line, 14-line and 8-line font data will be compiled in.
Without this option, the syscons driver will use whatever font is already loaded in the video
card, unless you explicitly load a software font at startup. See “EXAMPLES” below.

SC_NO_SUSPEND_VTYSWITCH
This option, which is also available as loader(8) tunable and sysctl(8) variable
hw.syscons.sc_no_suspend_vtswitch, disables switching between virtual terminals (graphics <->
text) during suspend/resume (ACPI and APM). Use this option if your system is freezing when you
are running X and trying to suspend.

The following options will remove some features from the syscons driver and save kernel memory.

SC_NO_CUTPASTE
This option disables ``copy and paste'' operation in virtual terminals.

SC_NO_FONT_LOADING
The syscons driver can load software fonts on some video cards. This option removes this feature.
Note that if you still wish to use the mouse with this option then you must also use the
SC_ALT_MOUSE_IMAGE option.

SC_NO_HISTORY
This option disables back-scrolling in virtual terminals.

SC_NO_SYSMOUSE
This option removes mouse support in the syscons driver. The mouse daemon moused(8) will fail if
this option is defined. This option implies the SC_NO_CUTPASTE option too.

Driver Flags
The following driver flags can be used to control the syscons driver. Driver flags can be set with the
hint.sc.0.flags tunable, either in /boot/device.hints, or else at the loader prompt (see loader(8)).

0x0080 (VESAMODE)
This option puts the video card in the VESA mode specified by /boot/device.hints variable
vesa_mode during kernel initialization. Note that in order for this flag to work, the kernel must
be compiled with the SC_PIXEL_MODE option explained above. A list of the available mode can be
obtained via vidcontrol(1).

0x0100 (AUTODETECT_KBD)
This option instructs the syscons driver to periodically scan for a keyboard device if it is not
currently attached to one. Otherwise, the driver only probes for a keyboard once during bootup.

Loader Tunables
These settings can be entered at the loader(8) prompt or in loader.conf(5).

kern.vty
When both syscons and vt(4) have been compiled into the kernel, the one to use for the system
console can be selected by setting this variable to ‘sc’ or ‘vt’. The GENERIC kernel uses vt(4)
when this value is not set.

FILES

       /dev/console
       /dev/consolectl
       /dev/ttyv?                      virtual terminals
       /etc/ttys                       terminal initialization information
       /usr/share/syscons/fonts/*      font files
       /usr/share/syscons/keymaps/*    key map files
       /usr/share/syscons/scrmaps/*    screen map files

EXAMPLES

As the syscons driver requires the keyboard driver and the video card driver, the kernel configuration
file should contain the following lines.

device atkbdc
device atkbd
device vga
device sc
device splash

You also need the following lines in /boot/device.hints for these drivers.

hint.atkbdc.0.at="isa"
hint.atkbdc.0.port="0x060"
hint.atkbd.0.at="atkbdc"
hint.atkbd.0.irq="1"
hint.vga.0.at="isa"
hint.sc.0.at="isa"

If you do not intend to load the splash image or use the screen saver, the last line is not necessary,
and can be omitted.

Note that the keyboard controller driver atkbdc is required by the keyboard driver atkbd.

The following lines will set the default colors. The normal text will be green on black background. The
reversed text will be yellow on green background. Note that you cannot put any white space inside the
quoted string, because of the current implementation of config(8).

options SC_NORM_ATTR=(FG_GREEN|BG_BLACK)
options SC_NORM_REV_ATTR=(FG_YELLOW|BG_GREEN)

The following lines will set the default colors of the kernel message. The kernel message will be
printed bright red on black background. The reversed message will be black on red background.

options SC_KERNEL_CONS_ATTR=(FG_LIGHTRED|BG_BLACK)
options SC_KERNEL_CONS_REV_ATTR=(FG_BLACK|BG_RED)

Provided SC_KERNEL_CONS_ATTR is not set, or is set to its default of bright white on black, the following
line will set 4 red-ish colors for printing kernel messages in colors depending on the CPU.

options SC_KERNEL_CONS_ATTRS=\"\x0c\x04\x40\x0e\"

The default scheme is probably better for up to 8 CPUs. Use a long string to get unique colors for more
than 8 CPUs.

To turn off all per-CPU coloring of kernel messages, set SC_KERNEL_CONS_ATTR to a non-default value, or
use the default in a pattern of length 1.

options SC_KERNEL_CONS_ATTRS=\"\x0f\"

The following example adds the font files cp850-8x16.fnt, cp850-8x14.font and cp850-8x8.font to the
kernel.

options SC_DFLT_FONT
makeoptions SC_DFLT_FONT=cp850
device sc

HISTORY

       The syscons driver first appeared in FreeBSD 1.0.

AUTHORS

       The syscons driver was written by Søren Schmidt <sos@FreeBSD.org>.   This  manual  page  was  written  by
       Kazutaka Yokota <yokota@FreeBSD.org>.

CAVEATS

       The amount of data that is possible to insert from the cut buffer is limited by the {MAX_INPUT}, a system
       limit  on  the  number  of bytes that may be stored in the terminal input queue - usually 1024 bytes (see
       termios(4)).

BUGS

       This manual page is incomplete and urgently needs revision.

Debian                                            June 2, 2018                                        SYSCONS(4)