I just built my own computer (first time I have done this) and I am currently connected to my monitor via HDMI using Linux Mint version 18.03. Though, while I know my monitor supports 1920x1080, it is currently set to 1024x768. When I go into my settings, this is the only option available. I don't have a dedicated GPU, only onboard Intel Graphics. I have tried changing it with xrandr and here is the output:

sam@trinity: xrandr
xrandr: failed to get size of gamma for output default
Screen 0: minimum 1024x768+0+0 0mm x 0mm
 1024x768 76.00*

sam@trinity: sudo cvt 1920 1080 60
[sudo] password for sam:
# 1920x1080 59.96 Hz (CVT 2.07M9) hsync: 67.16 kHz; pclk: 173.00 MHz
Modeline "1920x1080_60.00" 173.00 1920 2048 2248 2576 1080 1083 1088 1120 -hsync +vsync
sam@trinity ~ $ sudo xrandr --newmode "1920x1080_60.00" 173.00 1920 2048 2248 2576 1080 1083 1088 1120 -hsync +vsync
xrandr: Failed to get size of gamma for output default
sam@trinity ~ $ xrandr -q
xrandr: Failed to get size of gamma for output default
Screen 0: minimum 1024 x 768, current 1024 x 768, maximum 1024 x 768
default connected primary 1024x768+0+0 0mm x 0mm
 1024x768 76.00*
 1920x1080_60.00 (0x279) 173.000MHz -HSync +VSync
 h: width 1920 start 2048 end 2248 total 2576 skew 0 clock 67.16KHz
 v: height 1080 start 1083 end 1088 total 1120 clock 59.96Hz
sam@trinity ~ $ sudo xrandr --addmode default 1920x1080_60.00
xrandr: Failed to get size of gamma for output default

I am not sure where to go from here. From what I'm seeing, max supported resolution seems to be only 1024x768. Am I reading this correctly? Any suggestions?

Issue at Hand

You are unable to change your screen resolution to the maximum supported resolution of your monitor.

Solution

I am referencing this post by user Sylvain Pineau for this answer. First start by restarting X by running killall Xorg. Once you have done that please follow along with what user Sylvain Pineau suggests.

You don't need sudo to register the new mode with xrandr, try without sudo. Then you'll have to apply the new resolution with:

xrandr --addmode <your_connection_type> 1920_1080_60.00

Where is usually VGA1, DP1 or HDMI1. Check the output of xrandr to know the exact name of the connected output.

Try this, you may need to run the following line to add support for your desired resolution:

xrandr --newmode "[target_resolution]_60.00" -hsync +vsync

Conclusion

I am including a link to the xrandr manpage for reference as well. Please review all links before attempting any solution.

Please comment if you have any questions or issues with this answer. I appreciate feedback to correct any misconceptions and to improve my posts. I can update my answer as needed.

Best of Luck!