Flexible Strategies for Customizing Ubuntu Display Resolution

After installing the system, why is the maximum resolution only 800×600? How can you increase the monitor resolution? In many cases, these problems are caused by incorrect display configuration.

Quite a few readers have found that after running dpkg-reconfigure xserver-xorg and restarting the computer, X Window only offers two resolutions, 800×600 and 640×480, while the previously normal 1024×768 option disappears.

The key cause of this problem is usually an incorrect setting for the monitor's horizontal scan frequency range and vertical scan frequency range. Below are several relatively flexible solutions.

Modify the xorg.conf file

Identify the monitor's horizontal and vertical scan frequencies

You can use the following three methods to confirm the frequency ranges supported by the monitor.

  1. Look up the monitor manual and find the horizontal scan frequency and vertical scan frequency ranges. This is the most accurate and direct method.
  1. Use the ddcprobe command.
sudo ddcprobe

Example output:

...
monitorname: Topsonic
monitorrange: 28-49, 43-72
  1. Run the xvidtune command.

After starting xvidtune in the graphical interface, you can use the eight buttons in the middle to adjust the screen position and size, and you can also view the monitor's horizontal and vertical scan frequency ranges.

After clicking these buttons, you need to click Apply for the changes to take effect. If you are unsure, you can click Test first, confirm that everything is fine, and then click Apply.

Once the adjustment is satisfactory, click the Show button. When you exit xvidtune, the terminal window will also display the monitor's scan frequency range. Copy that line of parameters for later use.

xvidtune

Example output:

Vendor: , model:
Num hsync: 1, Num vsync: 1
hsync range 0: 28.00 - 49.00
vsync range 0: 43.00 - 72.00

Back up xorg.conf

Before making changes, back up the configuration file:

sudo cp /etc/X11/xorg.conf /etc/X11/xorg.conf.bak

Modify the xorg.conf file

Add the required resolutions and refresh rates to the xorg.conf file:

sudo gedit /etc/X11/xorg.conf

Find Section "Monitor" and modify the configuration according to the horizontal and vertical scan frequencies obtained above, for example:

Section "Monitor"
    Identifier "Topsonic"
    Option "DPMS"
    HorizSync 28-49
    VertRefresh 43-72
EndSection

Then find Section "Screen" and add the required resolutions to the SubSection "Display" for the corresponding color depth:

SubSection "Display"
    Depth 16
    Modes "1024x768" "832x624" "800x600" "720x400" "640x480"
EndSubSection

SubSection "Display"
    Depth 24
    Modes "1024x768" "832x624" "800x600" "720x400" "640x480"
EndSubSection

Here, we have only added the previously missing 1024×768 resolution. You can also add other resolutions supported by your monitor as needed.

Other methods

If you still find the method above a bit complicated, you can try reconfiguring Xorg:

sudo dpkg-reconfigure xserver-xorg

Follow the prompts step by step: choose "Yes" for "Attempt monitor auto-detection" → select the resolutions you want to keep → choose "Simple". After that, you only need to select the monitor size; for example, I chose "17 inches", and the remaining steps can use the default settings. This method usually works.

With the methods above, you can customize your monitor resolution in a fairly flexible way.

Leave a Reply