After copying AMI to another region, can't get DCV working again, low memory and black screen with mouse pointer

The issue you're experiencing with DCV after copying your AMI to another region is likely related to user permissions and file access problems. When you used rsync to copy the root volume during the volume resize process, this may have altered file ownership or permissions that are critical for DCV operation.

In Linux environments, DCV sessions can fail to start when there are permission issues with accessing certain files and folders. Specifically, the DCV session processes might not be authorized to access:

1. The log files in the Amazon DCV log directory
2. The home folder of the user

The "low memory" message followed by a black screen with only a mouse pointer suggests that the DCV session is starting but failing to properly initialize the desktop environment due to these permission issues.

To resolve this problem:

1. Ensure that the home folder of the user and all files it contains have the correct user ID (UID) permissions
2. Remove old Amazon DCV log files that might have incorrect permissions
3. Check the DCV logs in the /var/log/dcv/ directory for specific error messages

If you're using Ubuntu with a GUI environment like GNOME or XFCE, you might also need to verify that the terminal is properly sourcing the available profiles. You can do this by running:

source /etc/profile && source $HOME/.bashrc

Additionally, if you're using a GPU-accelerated instance (like g4dn), ensure that the NVIDIA drivers are properly installed and functioning in the new region, as DCV may be trying to use GPU acceleration but failing.
Sources
Linux Sessions fail to start after UID change - Amazon DCV
Troubleshooting issues in Amazon DCV - AWS ParallelCluster
Amazon DCV fails to create sessions on EC2 (Ubuntu 22.04 + g4dn + Isaac Sim Setup) | AWS re:Post