I had to use an adapter so I could plug an old monitor with VGA ports only into a somewhat old graphic card with HDMI outputs. The adapter worked great, but because of it, my Linux machine could no longer identify the display nor its optimal resolution and frequency. I was stuck in a 1024x768 resolution.

To fix that, first I had to go to the LG website and look up my monitor model (W1952TQ) to find out the correct settings. In there, I found the following specs:

Max resolution

1440 x 900 @ 75Hz

Vertical frequency

56 ~ 75 Hz

Horizontal frequency

28 ~ 83 Hz

After that, I read somewhere that I should add these parameters to my xorg.conf file. But this machine is running Ubuntu, and there is no such file. So I had to type the following for the file to be created:

nvidia-xconfig

After that a very basic xorg.conf is created inside /etc/X11. In that file, I added the following lines in the Monitor section:

HorizSync 28.0-83.0
VertRefresh 56.0-75.0

After that, I had to run cvt which is a helper program that generates the values that should be passed to xrandr to add the new resolution to the available resolutions:

cvt 1440 900 75

# The command returned the following line:
## 1440x900 74.98 Hz (CVT 1.30MA) hsync: 70.64 kHz; pclk: 136.75 MHz
# Modeline "1440x900_75.00" 136.75 1440 1536 1688 1936 900 903 909 943 -hsync +vsync

Which returned

After that, I created a shell script with the following content:

#!/bin/bash
xrandr --newmode "1440x900_75.00" 136.75 1440 1536 1688 1936 900 903 909 943 -hsync +vsync
xrandr --addmode DVI-I-0 1440x900_75.00
xrandr --output DVI-I-0 --mode 1440x900_75.00

I also had to give this script execution permissions:

chmod +x autoxrandr.sh

Now that we have all the necessary commands in a script, I added it to the list of auto-run commands upon Gnome logon by creating a .desktop file to ~/.config/autostart:

[Desktop Entry]
Name=Auto Xrandr Script
Exec=/path/to/the/script
Terminal=false
Type=Application
Hidden=true

Now, whenever I log in to Gnome, the script above will run and will set the monitor with the correct resolution.