Remote Desktop Access via DCV and VNC Connections
Last update: June 08, 2023
Establishing a remote desktop connection from one system to another allows the desktop on the remote computer (TACC resources) to be displayed on the local system (your desktop). For HPC purposes remote desktops are used for visualization applications and other graphics-library enabled applications.
Remote Desktop Methods
TACC provides three methods of setting up a remote desktop:
VNC connection: A (Virtual Network Computing) VNC connection allows you to harness TACC resources' compute or visualization nodes to display an image on your own desktop display. After logging on, submit a special interactive batch job that:
allocates one or more compute nodes
- starts a
vncserverprocess on the first allocated node
- sets up an SSH tunnel through the login node to the vncserver access port
vncserver process is running on the compute node and a tunnel through the login node is created, the job script writes the connection port to the job output file,
vncserver.out. Then, connect the VNC viewer application to that port. The remote system's desktop is then presented.
TACC Vis Portal: Available to all Frontera and Stampede2 users, the TACC Analysis Portal provides an easy-to-use web interface to submit a VNC job script.
DCV connection: Desktop Cloud Visualization (DCV) traffic is encrypted using Transport Layer Security (TLS) through your web browser, obviating the need to create a separate SSH tunnel. A DCV connection is easier to set up than a VNC connection, however TACC is limited to the number of concurrent DCV licenses. Stampede2 and Frontera are currently the only TACC resources allowing DCV connections. The DCV job script writes connection information to a file,
dcvserver.out. You can connect to a DCV session with any modern web browswer.
TACC Analysis Portal
Connect to the TACC Analysis Portal at https://tap.tacc.utexas.edu. Everyone with a project allocation on Frontera or Stampede2 may use the TACC Analysis Portal.
DCV & VNC at TACC
TACC resources Frontera, Stampede2 and Lonestar6 all offer remote desktop capabilities via a VNC (Virtual Network Computing) connection. Frontera and Stampede2 also provide remote desktop access through a DCV (Desktop Cloud Visualization) connection to one or more nodes.
TACC has a limited number of DCV licenses available, so concurrent DCV sessions may be limited. TACC has provided two DCV job scripts for two different scenarios:
/share/doc/slurm/job.dcv2vnc- request a DCV session, if none is available, then a VNC session is submitted
/share/doc/slurm/job.dcv- request a DCV session, if none is available, then exit
You can modify or overwrite script defaults with
sbatch command-line options:
-t hours:minutes:secondsmodify the job runtime
-A projectnamespecify the project/allocation to be charged
-N nodesspecify number of nodes needed
-p partitionspecify an alternate queue
sbatch options in the Stampede2 User Guide: Common
Table 1. Job Scripts
|System||Connection Type||Script Location||Description of Default Behavior||Frontera||DCV||
||Requests a DCV session, if no license is available then the job exits.
Requests 1 node for 2 hours in Frontera's
||Requests a DCV session, but if no DCV licenses are available then a VNC session is submitted.
Requests 1 node for 2 hours Frontera's
||Requests 1 node for 2 hours in Frontera's
||Stampede2||DCV||Requests a DCV session, if no license is available then the job exits.
Requests 1 node for 2 hours in Stampede2's
|DCV|| ||Request a DCV session, tried to launch a DCV session but if none is available then a VNC session is submitted.
Requests 1 node for 2 hours Stampede2's the
|VNC||Requests 1 node for 2 hours in Stampede2's
||Lonestar6||VNC||Requests 1 node for 2 hours in Lonestar6's
Start a DCV Session
Both Frontera and Stampede2 allow DCV connections. Follow the steps below to start an interactive DCV session on either resource. The command-line examples below demonstrate creating a session on Stampede2. You can follow the same steps to establish a session on Frontera.
Connect to Stampede2 or Frontera in your usual manner, e.g.:
login1$ ssh -l username stampede2.tacc.utexas.edu
Submit one of two standard job scripts. If you submit the
job.dcv2vncscript, then either a DCV or VNC session is created. The following instructions demonstrate submitting the
Copy into your home directory, then edit either of the job scripts listed above to include your project allocation:
#SBATCH -A projectname
or you can provide the allocation number on the command line as an argument to the
login1$ sbatch -A projectname /share/doc/slurm/job.dcv login1$ sbatch -A projectname /share/doc/slurm/job.dcv2vnc
In the following example we also override the time option, requesting one hour instead of the script's default of two hours.
login4(689)$ sbatch -A projectname -t 01:00:00 /share/doc/slurm/job.dcv ... --> Verifying access to desired queue (skx-dev)...OK --> Verifying job request is within current queue limits...OK --> Checking available allocation (TG-123456)...OK Submitted batch job 1965942
Poll the queue, waiting till the job runs...
You can poll the job's status with the
squeuecommand, waiting till the submitted job actually runs, or by waiting for the job output file, (
vncserver.outdepending on the connection type and job script submitted), to appear in the submission directory.
login4(690)$ squeue -u slindsey JOBID PARTITION NAME USER ST TIME NODES NODELIST(REASON) 1965942 skx-dev dcvserve slindsey R 0:16 1 c506-082
If your job could not acquire a DCV license and launched a VNC session instead, jump to step 3 of the VNC connection instructions below.
Display the contents of the job output file to extract the web URL.
Once the DCV job starts running, a file called
dcvserver.outwill be created in the submission directory.
login4(691)$ cat dcvserver.out TACC: job 1965942 execution at: Tue Aug 21 14:25:54 CDT 2018 TACC: running on node c506-082 TACC: local (compute node) DCV port is 8443 TACC: got login node DCV port 18606 TACC: Created reverse ports on Stampede2 logins TACC: Your DCV session is now running! TACC: To connect to your DCV session, please point a modern web browser to: TACC: https://stampede2.tacc.utexas.edu:18606
Load this generated URL in your favorite browser and then authenticate using your Stampede2 or Frontera password.
Start your graphics-enabled application. Once the desktop is generated (Figure 3.), you can launch your applications. Here we run a simple visualization program,
glxgears. (Figure 4.)
The "Terminal" button at the bottom of the DCV window creates a terminal without
To create an xterm with full
xterm &in the initial xterm window.
Once you've completed your work and closed the browser window, remember to kill the job you submitted in Step 2.
login4(692)$ scancel 1965942 login4(693)$ exit
Start a VNC Session
Follow the steps below to start an interactive session.
If this is your first time connecting to a resource, you must run
vncpasswd to create a password for your VNC servers. This should NOT be your login password! This mechanism only deters unauthorized connections; it is not fully secure, as only the first eight characters of the password are saved. All VNC connections are tunneled through SSH for extra security, as described below.
Connect to the TACC resource in your usual manner, e.g.:
login1$ ssh -l slindsey ls5.tacc.utexas.edu
Submit the standard job script,
job.vnc, see Table 1..
TACC has provided a VNC job script (
/share/doc/slurm/job.vnc) that requests one node in Frontera's
developmentqueue for two hours.
login1$ sbatch /share/doc/slurm/job.vnc
All arguments after the job script name are sent to the
vncservercommand. For example, to set the desktop resolution to 1440x900, use:
login1$ sbatch /share/doc/slurm/job.vnc -geometry 1440x900
Poll and wait till the job runs...
login1$ squeue -u slindsey JOBID PARTITION NAME USER ST TIME NODES NODELIST(REASON) 1974882 development vncserve slindsey STYLEBLUER 0:16 1 c455-084
Display the job's output file,
vncserver.out, to extract the port connection number:
job.vncscript starts a vncserver process and writes the connect port for the vncviewer to the output file,
vncserver.outin the job submission directory.
The lightweight window manager,
xfce, is the default VNC desktop and is recommended for remote performance. Gnome is available; to use gnome, open the
~/.vnc/xstartupfile (created after your first VNC session) and replace
gnome-session. Note that gnome may lag over slow internet connections.
Create an SSH Tunnel to Stampede2
TACC requires users to create an SSH tunnel from the local system to the Stampede2 login node to assure that the connection is secure. On a Unix or Linux system, execute the following command once the port has been opened on the Stampede2 login node:
In a new local terminal window, create the SSH tunnel:
localhost$ ssh -f -N -L xxxx:stampede2.tacc.utexas.edu:yyyy \ email@example.com
yyyyis the port number given by the vncserver batch job
xxxxis a port on the remote system. Generally, the port number specified on the Stampede2 login node,
yyyy, is a good choice to use on your local system as well
-finstructs SSH to only forward ports, not to execute a remote command
sshcommand into the background after connecting
-Lforwards the port
On Windows systems find the menu in the Windows SSH client where tunnels can be specified, and enter the local and remote ports as required, then
Connect the VNC viewer
Once the SSH tunnel has been established, use a VNC client to connect to the local port you created, which will then be tunneled to your VNC server on Stampede2. Connect to
xxxxis the local port you used for your tunnel. In the examples above, we would connect the VNC client to
localhost::xxxx. (Some VNC clients accept
TACC staff recommends the TigerVNC VNC Client, a platform independent client/server application.
Once the desktop is generated (Figure 6.), you can start your graphics-enabled application. Here we run a simple visualization program,
glxgears. (Figure 7.)
Once the desktop has been established an initial xterm window appears. (Figure 6.) This window manages the lifetime of the VNC server process. Killing this window (typically by typing
ctrl-Dat the prompt) will cause the vncserver to terminate and the original batch job to end.
Once you've completed your work and closed the browser window, remember to kill the job you submitted in Step 2.
login4(692)$ scancel 1974882 login4(693)$ exit
Sample VNC session
Submit a VNC job for user
localhost$ ssh firstname.lastname@example.org ... login4(804)$ sbatch -A TG-123456 -t 01:00:00 /share/doc/slur m/job.vnc ... --> Verifying access to desired queue (development)...OK --> Verifying job request is within current queue limits...OK --> Checking available allocation (UserServStaff)...OK Submitted batch job STYLEBLUE1974882 login4(805)$ squeue -u slindsey JOBID PARTITION NAME USER ST TIME NODES NODELIST(REASON) 1974882 development vncserve slindsey R 0:16 1 c455-084 login4(806)$ cat vncserver.out job execution at: Wed Aug 22 15:43:46 CDT 2018 running on node c455-084 using default VNC server /bin/vncserver memory limit set to 93767542 kilobytes set wayness to got VNC display :1 local (compute node) VNC port is 5901 got login node VNC port 18455 Created reverse ports on Stampede2 logins Your VNC server is now running! To connect via VNC client: STYLEBLUESSH tunnel port 18455 to stampede2.tacc.utexas.edu:18455 Then connect to localhost::18455 login4(807)$ scancel 1974882 login4(808)$ squeue -u slindsey JOBID PARTITION NAME USER ST TIME NODES NODELIST(REASON) login4(809)$ exit logout Connection to stampede2.tacc.utexas.edu closed. bash-3.2$ exit
Create the SSH tunnel from your local machine to Stampede2
localhost$ ssh -f -N -L 18455:stampede2.tacc.utexas.edu:18455 email@example.com ... Password: TACC Token Code: localhost$
Running Apps on the Desktop
From an interactive desktop, applications can be run from icons or from
xterm command prompts.
See the Stampede2 User Guide Visualization and Frontera User Guide Visualization sections for details on running parallel applications on the desktop.