fbset - show and modify frame buffer device settings


fbset [''options''? [''mode''?


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fbset is a system utility to show or change the settings of the frame buffer device. The frame buffer device provides a simple and unique interface to access different kinds of graphic displays.

Frame buffer devices are accessed via special device nodes located in the /dev directory. The naming scheme for these nodes is always fb__nn'' is the number of the used frame buffer device.

fbset uses its own video mode database located in /etc/fb.modes. An unlimited number of video modes can be defined in this database. For further information see fb.modes(5).


If no option is given, fbset will display the current frame buffer settings.

General options:

--help, -h

display usage information

--now, -n

change the video mode immediately. If no frame buffer device is given via -fb , then this option is activated by default

--show, -s

display the video mode settings. This is the default if no further option or only a frame buffer device via -fb is given

--info, -i

display all available frame buffer information

--verbose, -v

display information about what fbset is currently doing

--version, -V

display the version information about fbset

--xfree86, -x

display the timing information as it's needed by XFree86

Frame buffer device nodes:

-fb __device

device gives the frame buffer device node. If no device via -fb is given, /dev/fb0 is used

Video mode database:

-db __file

set an alternative video mode database file (default is /etc/fb.modes), see also fb.modes(5)

Display geometry:

-xres __value

set visible horizontal resolution (in pixels)

-yres __value

set visible vertical resolution (in pixels)

-vxres __value

set virtual horizontal resolution (in pixels)

-vyres __value

set virtual vertical resolution (in pixels)

-depth __value

set display depth (in bits per pixel)

--geometry, -g ...

set all geometry parameters at once in the order xresyresvxres vyresdepth-g__ 640 400 640 400 4


make the physical resolution match the virtual resolution

Display timings:

-pixclock __value

set the length of one pixel (in picoseconds). Note that the frame buffer device may only support some pixel lengths

-left __value

set left margin (in pixels)

-right __value

set right margin (in pixels)

-upper __value

set upper margin (in pixel lines)

-lower __value

set lower margin (in pixel lines)

-hslen __value

set horizontal sync length (in pixels)

-vslen __value

set vertical sync length (in pixel lines)

--timings, -t ...

set all timing parameters at once in the order pixclockleft rightupper lowerhslen vslen-g__ 35242 64 96 35 12 112 2

Display flags:

-hsync {low|high}

set the horizontal sync polarity

-vsync {low|high}

set the vertical sync polarity

-csync {low|high}

set the composite sync polarity

-extsync {false|true}

enable or disable external resync. If enabled the sync timings are not generated by the frame buffer device and must be provided externally instead. Note that this option may not be supported by every frame buffer device

-bcast {false|true}

enable or disable broadcast modes. If enabled the frame buffer generates the exact timings for several broadcast modes (e.g. PAL or NTSC). Note that this option may not be supported by every frame buffer device

-laced {false|true}

enable or disable interlace. If enabled the display will be split in two frames, each frame contains only even and odd lines respectively. These two frames will be displayed alternating, this way twice the lines can be displayed and the vertical frequency for the monitor stays the same, but the visible vertical frequency gets halved

-double {false|true}

enable or disable doublescan. If enabled every line will be displayed twice and this way the horizontal frequency can easily be doubled, so that the same resolution can be displayed on different monitors, even if the horizontal frequency specification differs. Note that this option may not be supported by every frame buffer device

Display positioning:

-move {left|right|up|down}

move the visible part of the display in the specified direction

-step __value

set step size for display positioning (in pixels or pixel lines), if -step is not given display will be moved 8 pixels horizontally or 2 pixel lines vertically


To set the used video mode for X insert the following in rc.local:

fbset -fb /dev/fb0 vga

and make the used frame buffer device known to X:

export FRAMEBUFFER=/dev/fb0


/dev/fb* /etc/fb.modes


fb.modes(5), fbdev(4)?


Geert Uytterhoeven

Roman Zippel

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