Note: credit to and retrieved from https://wiki.ubuntu.com/X/Config/Resolution
- 1 TableOfContents
- 1.1 Resetting an out-of-range resolution
- 1.2 Dynamically testing different resolutions
- 1.3 Adding undetected resolutions
- 1.4 Setting xrandr changes persistently
- 1.4.1 Setting xrandr commands in .xprofile
- 1.4.2 Setting xrandr commands in kdm/gdm startup scripts
- 1.4.3 Setting resolution changes in xorg.conf
- 1.4.4 Setting resolution changes in xorg.conf -- resolution lower than expected
- 1.5 Obtaining modelines from Windows program PowerStrip
Resetting an out-of-range resolution
If you set a resolution inappropriate for your monitor in the Screen Resolution GUI tool, you can reset it by running rm ~/.config/monitors.xml from a terminal.
Dynamically testing different resolutions
You can either use the Screen Resolution GUI tool to experiment with different resolutions, or the more powerful xrandr command-line tool:
shows you the names of different outputs available on your system (LVDS, VGA-0, etc.) and resolutions available on each:
Screen 0: minimum 320 x 200, current 1400 x 1050, maximum 1400 x 1400 VGA disconnected (normal left inverted right x axis y axis) LVDS connected 1400x1050+0+0 (normal left inverted right x axis y axis) 286mm x 214mm 1400x1050 60.0*+ 50.0 [...]
You can direct xrandr to set a different resolution like this:
$ xrandr --output LVDS --mode 1024x768
The refresh rate may also be changed, either at the same time or independently:
$ xrandr --output LVDS --mode 1024x768 --rate 75
Note that changes you make using xrandr only last through the current session. xrandr has a lot more capabilities - see man xrandr for details.
Adding undetected resolutions
Due to buggy hardware or drivers, your monitor's correct resolutions may not always be detected. For example, the EDID data block queried from your monitor may be incorrect.
If the mode already exists, but just isn't associated for the particular output, you can add it like this:
$ xrandr --addmode S-video 800x600
If the mode doesn't yet exist, you'll need to create it first by specifying a modeline:
$ xrandr --newmode <Mode Line>
You may create a modeline using the gtf or cvt utility. For example, if you want to add a mode with resolution 800x600, you can enter the following command: (The output is shown following.)
$ cvt 800 600 # 800x600 59.86 Hz (CVT 0.48M3) hsync: 37.35 kHz; pclk: 38.25 MHz Modeline "800x600_60.00" 38.25 800 832 912 1024 600 603 607 624 -hsync +vsync
Then copy the information after the word "Modeline" into the xrandr command:
$ xrandr --newmode "800x600_60.00" 38.25 800 832 912 1024 600 603 607 624 -hsync +vsync
Setting xrandr changes persistently
There are several ways to make xrandr customizations permanent from session to session: a) .xprofile, b) kdm/gdm, c) xorg.conf. Each of these mechanisms will be discussed in turn.
Setting xrandr commands in .xprofile
A user's ~/.xprofile file is executed on Xorg startup if it exists and is executable. You can copy and paste xrandr command line strings into this file so they're executed when you log in. For example:
$ xrandr --output VGA-0 --mode 800x600
There are two disadvantages to using .xprofile for xrandr settings. First, it occurs fairly late in the startup process, so you'll see some resolution resizing during the initial screen draw; in some cases panel windows may resize improperly as a result. Second, as this is a per-user setting, it won't affect the resolutions of other users, nor will it alter the resolution on the login screen.
Setting xrandr commands in kdm/gdm startup scripts
Both KDM and GDM have startup scripts that are executed when X is initiated. For GDM, these are in /etc/gdm/ , while for KDM this is done at /etc/kde4/kdm/Xsetup. In either case, you can paste in an xrandr command line string into one of these scripts. For GDM, try putting them right before initctl -q emit login-session-start DISPLAY_MANAGER=gdm in /etc/gdm/Init/Default
This process requires root access and mucking around in system config files, but will take effect earlier in the startup process than using .xprofile, and will apply to all users including the login screen.
Setting resolution changes in xorg.conf
While xorg.conf is largely empty these days, it can still be used for setting up resolutions. For example:
Section "Monitor" Identifier "External DVI" Modeline "1280x1024_60.00" 108.88 1280 1360 1496 1712 1024 1025 1028 1060 -HSync +Vsync Option "PreferredMode" "1280x1024_60.00" EndSection Section "Device" Identifier "ATI Technologies, Inc. M22 [Radeon Mobility M300]" Driver "ati" Option "Monitor-DVI-0" "External DVI" EndSection Section "Screen" Identifier "Primary Screen" Device "ATI Technologies, Inc. M22 [Radeon Mobility M300]" DefaultDepth 24 SubSection "Display" Depth 24 Modes "1280x1024" "1024x768" "640x480" EndSubSection EndSection Section "ServerLayout" Identifier "Default Layout" Screen "Primary Screen" EndSection
See man xorg.conf for full details on how to craft an xorg.conf file.
Setting resolution changes in xorg.conf -- resolution lower than expected
Try this first
If you video card is recognized but the resolution is lower than you expect, you may try this.
Background: ATI X1550 based video card and two LCD monitors DELL 2408(up to 1920x1200) and Samsung 206BW(up to 1680x1050). Upon first login after installation, the resolution default to 1152x864. xrandr does not list any resolution higher than 1152x864. You may want to try editing /etc/X11/xorg.conf, add a section about virtual screen, logout, login and see if this helps. If not then read on.
Change the default xorg.conf
Section "Device" Identifier "Configured Video Device" EndSection Section "Monitor" Identifier "Configured Monitor" EndSection Section "Screen" Identifier "Default Screen" Monitor "Configured Monitor" Device "Configured Video Device" EndSection
Section "Monitor" Identifier "Configured Monitor" EndSection Section "Screen" Identifier "Default Screen" Monitor "Configured Monitor" Device "Configured Video Device" -> SubSection "Display" -> Virtual 3600 1200 -> EndSubSection EndSection Section "Device" Identifier "Configured Video Device" EndSection
About the numbers: DELL on the left and Samsung on the right. So the virtual width is of sum of both LCD width 3600=1920+1680; Height then is figured as the max of them, which is max(1200,1050)=1200. If you put one LCD above the other, use this calculation instead: (max(width1, width2), height1+height2).
Use cvt/xrandr tool to add the highest mode the LCD can do
The actual order was different, as I tried to add new mode to one LCD at a time. Below is the combined/all-in-one quote
aa@aa-desktop:/$ cvt 1920 1200 60 # 1920x1200 59.88 Hz (CVT 2.30MA) hsync: 74.56 kHz; pclk: 193.25 MHz Modeline "1920x1200_60.00" 193.25 1920 2056 2256 2592 1200 1203 1209 1245 -hsync +vsync aa@aa-desktop:/$ cvt 1680 1050 60 # 1680x1050 59.95 Hz (CVT 1.76MA) hsync: 65.29 kHz; pclk: 146.25 MHz Modeline "1680x1050_60.00" 146.25 1680 1784 1960 2240 1050 1053 1059 1089 -hsync +vsync aa@aa-desktop:/$ xrandr --newmode "1920x1200_60.00" 193.25 1920 2056 2256 2592 1200 1203 1209 1245 -hsync +vsync aa@aa-desktop:/$ xrandr --newmode "1680x1050_60.00" 146.25 1680 1784 1960 2240 1050 1053 1059 1089 -hsync +vsync aa@aa-desktop:/$ xrandr --addmode DVI-1 "1920x1200_60.00" aa@aa-desktop:/$ xrandr --addmode DVI-0 "1680x1050_60.00"
Obtaining modelines from Windows program PowerStrip
X.Org Wiki [an article about this].