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SYSCONS(4) DragonFly Kernel Interfaces Manual SYSCONS(4)
NAME
syscons, sc - the console driver
SYNOPSIS
options MAXCONS=N
options SC_ALT_MOUSE_IMAGE
options SC_DISABLE_DDBKEY
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_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_REV_ATTR=_attribute_
options SC_BORDER_COLOR=_attribute_
options SC_DFLT_FONT
makeoptions SC_DFLT_FONT=_font_name_
device sc0 at isa? [flags flags]
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 drivers (amdgpu(4), i915(4), radeon(4), or
vga(4)). Please see DRIVER CONFIGURATION below on how to make the
console work with amdgpu(4), i915(4) or radeon(4).
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 ttyv10
Alt-F2 ttyv1 Alt-F8 ttyv7 Shift-Alt-F2 ttyv11
Alt-F3 ttyv2 Alt-F9 ttyv8 Shift-Alt-F3 ttyv12
Alt-F4 ttyv3 Alt-F10 ttyv9 Shift-Alt-F4 ttyv13
Alt-F5 ttyv4 Alt-F11 ttyv10 Shift-Alt-F5 ttyv14
Alt-F6 ttyv5 Alt-F12 ttyv11 Shift-Alt-F6 ttyv15
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
Loader Tunables
The following tunables are available and can be set in loader.conf(5).
kern.kms_console Setting this tunable to 0 disables experimental
framebuffer support in conjunction with the
amdgpu(4), i915(4) or radeon(4) drivers. It is 1
by default.
kern.kms_columns The number of columns to use in conjunction with
the amdgpu(4), i915(4) and radeon(4) drivers. The
font size is scaled to match the requested number
of columns. This requires kern.kms_console to be
set to 1. By default, syscons tries to find a more
or less pleasant looking default. Setting
kern.kms_columns to a negative value turns off
scaling. Please note that ttyv0 is restricted to
160 columns and any setting of kern.kms_columns
resulting in a higher number of columns will be
ignored for ttyv0, but applied to other virtual
terminals.
Sysctl Variables
The following sysctl(8) variable is available and can be either set via
sysctl.conf(5) or from the command line.
kern.syscons_async Set to 1 to enable asynchronous bulk
framebuffer updates. It is intended to
help with sound(4) stuttering when a high
resolution syscons scrolls during playback.
It is not enabled by default because on
certain machines it has led to subtle
issues with for example ddb(4).
kern.syscons.enable_bell Enable the terminal bell. On by default.
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_DISABLE_DDBKEY
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 (DDB) by pressing the key
combination. DDB will still be invoked when the kernel panics or
hits a break point if it is included in the kernel.
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.
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.
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_REV_ATTR=_attribute_
SC_BORDER_COLOR=_attribute_
These options will set the default colors. Available colors are
defined in <machine/pc/display.h>. See EXAMPLES below.
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.
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.
They can be set in the kernel configuration file.
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.
IOCTLS
The following ioctl(2) commands are defined for the syscons driver in
<sys/consio.h>.
KDGETMODE int *mode
KDSETMODE int *mode
Get or set the mode of the current (virtual) console. The mode can
be one of:
KD_TEXT same as KD_TEXT0
KD_TEXT0 Text mode, restore fonts and palette
KD_GRAPHICS Graphics mode
KD_TEXT1 Text mode, don't restore fonts and palette
KD_PIXEL Raster (pixel) text mode
KDSBORDER int *color
Set the border color of the current (virtual) console.
KDRASTER scr_size_t *sizes
Set raster (pixel) text mode and adjust the current (virtual)
console's geometry and font size. The scr_size_t argument structure
is as follows:
struct _scr_size {
int scr_size[3];
};
GIO_SCRNMAP scrmap_t *map
PIO_SCRNMAP scrmap_t *map
Get or set the screen map for the current (virtual) console. The
scrmap_t argument structure is defined as follows:
struct _scrmap {
char scrmap[256];
};
GIO_ATTR int *attr
Get the current text attribute.
GIO_COLOR int *color
Get the current text color.
CONS_CURRENT int *type
Get the adapter type. This is equivalent to FBIO_ADPTYPE.
CONS_GET int *mode
Get the current video mode. This is equivalent to FBIO_GETMODE.
CONS_SET int *mode
Set the current video mode. This is equivalent to FBIO_SETMODE.
CONS_BLANKTIME int *time
Set the screen saver blank interval (in seconds).
CONS_CURSORTYPE int *type
Set the text cursor shape. The argument type can be one or more of
the following:
CONS_BLINK_CURSOR Set for a blinking cursor, unset for a non-
blinking cursor.
CONS_CHAR_CURSOR Set for an underscore-shaped cursor, unset for a
rectangle.
CONS_BELLTYPE int *type
Set the bell type. The argument type is one or more of:
CONS_VISUAL_BELL Set for a visual bell, unset for an audible bell.
CONS_QUIET_BELL Set to enable the bell, unset to disable it.
CONS_HISTORY int *size
Set the history (scroll back) buffer size (in lines).
CONS_CLRHIST
Clear the history (scroll back) buffer.
CONS_IDLE int *idle
Check if the (virtual) console has been idle.
CONS_SAVERMODE int *mode
Set the screen saver mode. The argument mode can be one of:
CONS_NO_SAVER Disable screen saver
CONS_USR_SAVER Enable screen saver
CONS_LKM_SAVER Add a new screen saver
CONS_SAVERSTART int *start
Start or stop the screen saver.
PIO_FONT8x8 fnt8_t *font
GIO_FONT8x8 fnt8_t *font
Get or set the 8x8 font. The fnt8_t argument structure is defined
as follows:
struct fnt8 {
char fnt8x8[8*256];
};
PIO_FONT8x14 fnt14_t *font
GIO_FONT8x14 fnt14_t *font
Get or set the 8x14 font. The fnt14_t argument structure is defined
as follows:
struct fnt14 {
char fnt8x14[14*256];
};
PIO_FONT8x16 fnt16_t *font
GIO_FONT8x16 fnt16_t *font
Get or set the 8x16 font. The fnt16_t argument structure is defined
as follows:
struct fnt16 {
char fnt8x16[16*256];
};
CONS_GETINFO vid_info_t *info
Get information about the current video mode. The vid_info_t
structure is defined as follows:
struct vid_info {
short size;
short m_num;
u_short font_size;
u_short mv_row, mv_col;
u_short mv_rsz, mv_csz;
struct colors mv_norm,
mv_rev,
mv_grfc;
u_char mv_ovscan;
u_char mk_keylock;
};
CONS_GETVERS int *version
Get the version of the driver.
CONS_CURRENTADP int *adapter
Get the video adapter index. This is equivalent to FBIO_ADAPTER.
CONS_ADPINFO video_adapter_info_t *info
Get the video adapter information. This is equivalent to
FBIO_ADPINFO.
CONS_MODEINFO video_info_t *info
Get the video mode information. This is equivalent to
FBIO_MODEINFO.
CONS_FINDMODE video_info_t *info
Find a video mode. This is equivalent to FBIO_FINDMODE.
CONS_SETWINORG u_int *origin
Set the frame buffer window origin. This is equivalent to
FBIO_SETWINORG.
CONS_SETKBD int *kbd
Set a new keyboard.
CONS_RELKBD
Release the current keyboard.
CONS_SCRSHOT scrshot_t *data
Make a snapshot of the current video buffer. The scrshot_t
structure is defined as:
struct scrshot {
int xsize;
int ysize;
u_int16_t* buf;
};
CONS_GETTERM term_info_t *info
CONS_SETTERM term_info_t *info
Get or set terminal characteristics. The term_info_t structure is
defined as:
struct term_info {
int ti_index;
int ti_flags;
u_char ti_name[TI_NAME_LEN];
u_char ti_desc[TI_DESC_LEN];
};
VT_OPENQRY int *term
Get the next available terminal.
VT_SETMODE vtmode_t *mode
VT_GETMODE vtmode_t *mode
Get or set the terminal switching mode. The vtmode_t argument
structure is defined as follows:
struct vt_mode {
char mode;
char waitv;
short relsig;
short acqsig;
short frsig;
};
VT_RELDISP int *ack
Acknowledge the release or acquisition of a terminal. The ack
argument can be one of:
VT_FALSE The user refuses to release the screen, abort
VT_TRUE The user has released the screen, go on
VT_ACKACQ Acquisition of the screen acknowledged, switch completed
VT_ACTIVATE int *term
Activate the specified terminal.
VT_WAITACTIVE int *term
Wait until the specified terminal is active.
VT_GETACTIVE int *term
Get the currently active terminal.
VT_GETINDEX int *index
Get the index of the terminal.
VT_LOCKSWITCH int *lock
Prevent or permit terminal switching.
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 atkbdc0 at isa? port IO_KBD
device atkbd0 at atkbdc? irq 1
device vga0 at isa?
device sc0 at isa?
pseudo-device splash
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)
The following line will set the default border color of the terminal. If
the console is in framebuffer mode, or in raster (pixel) text mode, a
thin green border will be visible around the terminal if the screen size
is not an exact multiple of the font size. This border area can be much
larger if the column or row count is explicitly specified (for example
when using the kern.kms_columns tunable).
options SC_BORDER_COLOR=FG_GREEN
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 sc0 at isa?
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)).
SEE ALSO
kbdcontrol(1), login(1), vidcontrol(1), atkbd(4), atkbdc(4), keyboard(4),
screen(4), splash(4), sysmouse(4), ukbd(4), vga(4), kbdmap(5),
rc.conf(5), ttys(5), getty(8), kldload(8), moused(8)
HISTORY
The syscons driver first appeared in FreeBSD 1.0.
AUTHORS
The syscons driver was written by Soren Schmidt <sos@FreeBSD.org>. This
manual page was written by Kazutaka Yokota <yokota@FreeBSD.org> and
Sascha Wildner.
BUGS
This manual page is incomplete and needs revision.
DragonFly 6.5-DEVELOPMENT August 6, 2025 DragonFly 6.5-DEVELOPMENT