(3.5.0 and earlier) DCV virtual session on Ubuntu 20.04 might show a black screen

The issue

ParallelCluster 3.5.0 and earlier versions are impacted by a known issue with DCV 2022.1-13300 and earlier, which intermittently causes a blank (black) screen in virtual sessions on Ubuntu 20.04. The issue triggers at the start of a virtual session due to a race condition, therefore it may happen for some virtual sessions and not others.

Affected versions

• ParallelCluster version 3.5.0 and earlier are impacted.

Mitigation

Upgrading DCV on the head node solves the problem. Below is a guide for upgrading DCV for your reference:

1. SSH into the head node of the affected cluster:

pcluster ssh --cluster-name <cluster-name>

2. List active DCV sessions

dcv list-sessions

3. Close running DCV sessions (You may need to run the command multiple times if there are multiple sessions)

dcv close-session <session-id>

4. Stop and disable the DCV server

sudo systemctl stop dcvserver
sudo systemctl disable dcvserver

5. Backup the DCV configuration file

sudo cp /etc/dcv/dcv.conf /etc/dcv/dcv.conf.bak

6. Upgrade DCV (You can simply follow the commands below or learn more at https://docs.aws.amazon.com/dcv/latest/adminguide/setting-up-installing-linux-server.html#linux-server-install)

• Install the NICE DCV server, remember to enter Y to install the new version during the installation

wget https://d1uj6qtbmh3dt5.cloudfront.net/NICE-GPG-KEY
gpg --import NICE-GPG-KEY
wget https://d1uj6qtbmh3dt5.cloudfront.net/2022.2/Servers/nice-dcv-2022.2-14521-ubuntu2004-x86_64.tgz
tar -xvzf nice-dcv-2022.2-14521-ubuntu2004-x86_64.tgz && cd nice-dcv-2022.2-14521-ubuntu2004-x86_64
sudo apt install ./nice-dcv-server_2022.2.14521-1_amd64.ubuntu2004.deb

• Install nice-dcv-web-viewer, add the dcv user to the video group, install nice-xdcv and nice-dcv-gl

sudo apt install ./nice-dcv-web-viewer_2022.2.14521-1_amd64.ubuntu2004.deb
sudo usermod -aG video dcv
sudo apt install ./nice-xdcv_2022.2.519-1_amd64.ubuntu2004.deb
sudo apt install ./nice-dcv-gl_2022.2.1012-1_amd64.ubuntu2004.deb

7. Restore DCV configuration file

sudo mv /etc/dcv/dcv.conf.bak /etc/dcv/dcv.conf

8. Restart and enable the DCV server

sudo systemctl restart dcvserver
sudo systemctl enable dcvserver