For Nvidia GPUs there is a tool nvidia-smi that can show memory usage, GPU utilization and temperature of GPU.
For Intel GPU's you can use the intel-gpu-tools.
AMD has two options
fglrx (closed source drivers):
aticonfig --odgc --odgtAnd for mesa (open source drivers), you can use RadeonTop
sudo apt install radeontop radeontop
Source:GPU usage monitoring
Answer from Mitch on askubuntu.comFor Nvidia GPUs there is a tool nvidia-smi that can show memory usage, GPU utilization and temperature of GPU.
For Intel GPU's you can use the intel-gpu-tools.
AMD has two options
fglrx (closed source drivers):
aticonfig --odgc --odgtAnd for mesa (open source drivers), you can use RadeonTop
sudo apt install radeontop radeontop
Source:GPU usage monitoring
You can use gpustat, which is a simple command-line script (wrapper for nvidia-smi) for querying and monitoring GPU status:

Is there a way to monitor my vram and Temp for my GPU in ubuntu?
GPU usage monitoring (CUDA) - Unix & Linux Stack Exchange
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Just built a PC and am using ubuntu as my daily driver. Super sick. I have an amd 9060xt 16gb. I want to monitor it's temp and vram usage. I can't find any straight forward ways to do it. Anyone else know of a way?
For Nvidia GPUs there is a tool nvidia-smi that can show memory usage, GPU utilization and temperature of GPU. There also is a list of compute processes and few more options but my graphic card (GeForce 9600 GT) is not fully supported.
Sun May 13 20:02:49 2012
+------------------------------------------------------+
| NVIDIA-SMI 3.295.40 Driver Version: 295.40 |
|-------------------------------+----------------------+----------------------+
| Nb. Name | Bus Id Disp. | Volatile ECC SB / DB |
| Fan Temp Power Usage /Cap | Memory Usage | GPU Util. Compute M. |
|===============================+======================+======================|
| 0. GeForce 9600 GT | 0000:01:00.0 N/A | N/A N/A |
| 0% 51 C N/A N/A / N/A | 90% 459MB / 511MB | N/A Default |
|-------------------------------+----------------------+----------------------|
| Compute processes: GPU Memory |
| GPU PID Process name Usage |
|=============================================================================|
| 0. Not Supported |
+-----------------------------------------------------------------------------+
For linux, use nvidia-smi -l 1 will continually give you the gpu usage info, with in refresh interval of 1 second.