Sign up ×
Ask Ubuntu is a question and answer site for Ubuntu users and developers. It's 100% free.

I know how to modify xorg.conf and get it to start at about 1024x768, but I can't get it to start at 1600x1200. It is quite an inconvenience to have to go and manually start them up each time. We are using these servers as automation agents. We are browser testing using sikuli so we can't go headless.

share|improve this question
This answer may help you. – Takkat Aug 16 '11 at 9:02
@Takkat, this works if ubuntu started with the monitor plugged in. However, if I do those steps after starting without the monitor plugged in, then I just get 1024x768. – justspamjustin Aug 17 '11 at 16:45

1 Answer 1

By default, X will use DDC to probe the monitor for its supported resolutions. If the monitor is not plugged in, then this will not be possible. If you know the characteristics of the monitor, you can program in additional modes through the xorg.conf file.

If you haven't already, add a Monitor section. This can be hooked in in one of two ways: either a Monitor "$IDENTIFIER" directive in the Screen section (the old way), or a Option "monitor-$OUTPUT" "$IDENTIFIER" directive in the Device section (the new multi-head aware way). If you use the second method, it uses the same output names as the xrandr utility.

In the Monitor section, add one or more ModeLine directives for each of the modes you want to program. According to the man page, the format is as follows:

ModeLine "name" clock hdisp hsyncstart hsyncend htotal vdisp vsyncstart vsyncend vtotal options

If the monitor is plugged in, you should be able to get this information from the xrandr --verbose command. For instance, if it shows the following:

  1920x1080 (0x59)  148.5MHz +HSync +VSync *current +preferred
        h: width  1920 start 2008 end 2052 total 2200 skew    0 clock   67.5KHz
        v: height 1080 start 1084 end 1089 total 1125           clock   60.0Hz

Then the corresponding ModeLine would be:

ModeLine "1920x1080" 148.5 1920 2008 2052 2200 1080 1084 1089 1125 +HSync +VSync

You should then be able to configure that mode even though the monitor is not initially connected.

share|improve this answer
new ModeLines can be generated with gtf – Takkat Aug 16 '11 at 9:03
Ok. I tried this configuration. And it didn't work. I got the modeline from gtf and everything. What is wrong? – justspamjustin Aug 16 '11 at 23:16
You need to link reference the monitor section in the screen section with Monitor "Monitor1". – James Henstridge Aug 17 '11 at 0:02
@James Henstridge, So what you are saying is that this should work then? – justspamjustin Aug 17 '11 at 15:47

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.