I recently had an issue where my new 4k Dell U2720Q wasn’t showing up at full resolution in Kali Linux. The monitor is connected to a Macbook Pro via USB-C and the VM is running on a VMware ESXi 6.7 U2 release. My monitor maxes out at 3840×2160 60 Hz. Kali was seeing the 60hz, but not the full 3840×2160, just 2560×1600.

I originally used xrandr and gtf, but I noticed that as soon as I clicked apply, the VM froze and became completely unresponsive. What I failed to realize was that in ESXi, the VM was set to something like 4 MB of video RAM. Zeroing in on this issue, I wasn’t sure how much video RAM to add.

I found this on Quora: https://www.quora.com/How-much-VRAM-do-I-need-to-run-4K-and-5K-smoothly and set my video RAM to around 130 MB just to be safe.

I then rebooted and followed the steps outlined here: https://gist.github.com/debloper/2793261

➜ ~ gtf 3840 2160 60
3840x2160 @ 60.00 Hz (GTF) hsync: 134.10 kHz; pclk: 712.34 MHz
Modeline "3840x2160_60.00" 712.34 3840 4152 4576 5312 2160 2161 2164 2235 -HSync +Vsync

➜ ~ xrandr --newmode "3840x2160_60.00" 712.34 3840 4152 4576 5312 2160 2161 2164 2235 -HSync +Vsync

➜ ~ xrandr --addmode Virtual1 "3840x2160_60.00"

➜ ~ xrandr --output Virtual1 --mode "3840x2160_60.00"

After following these steps, the new resolution 3840×2160 at 60 Hz showed up in the display manager. I selected, applied, and it worked.