Remote Development with VS Code

You can use Visual Studio Code with CRCD in three ways. Pick based on how much setup you want and whether you'd rather work in a browser or in your own local VS Code:

Method	Where VS Code runs	Best when
Code Server	In your browser, via Open OnDemand	You want the quickest start with nothing to install
VS Code via VNC	In a browser desktop (TurboVNC), via Open OnDemand	You want the full desktop VS Code UI in the browser
Remote tunnel	Your local VS Code, connected to a compute node	You want your own VS Code, extensions, and settings against cluster resources

The first two run through Open OnDemand and need no local setup. The tunnel is the most powerful but the most involved.

Code-Server

Code-Server runs VS Code on a compute node and serves it to your browser.

Once you login to https://ondemand.htc.crc.pitt.edu using your Pitt credentials (username in lowercase + Pitt password), you can click on Code Server from the Pinned Apps to bring up the job submission form

Installing extensions

Install extensions from the Extensions sidebar (only needed the first time, or when you need new ones). For example, search "Jupyter" in Extensions: Marketplace and click Install; extensions are stored under ~/.local/share/code-server. You can then open Jupyter notebooks.

Using a conda environment

To run notebooks against a specific conda environment, open the Command Palette, type Python: Select Interpreter, and enter the path to that environment's python. For example, the cell2location environment installed at /software/rhel9/manual/install/cell2location/0.1.4/python3.11/bin/python. (Install the Python extension first if you haven't.) See Python for creating your own environments.

VS Code via VNC

Log on to ondemand.htc.crc.pitt.edu, click Interactive Apps → VSCode on htc, choose a version, cores, and hours, then Launch. VS Code runs inside a TurboVNC desktop session in your browser.

Remote tunnel

This connects the VS Code installed on your own machine to a CRCD compute node using the Remote-SSH extension.

This is the advanced option

It requires SSH key setup and an SSH config. If you just want VS Code quickly, use Code Server above.

Prerequisites

• The latest VS Code on your local machine.
• The Remote Development extension pack.

One-time setup

1. Set up passwordless SSH. The tunnel needs your public key installed on the login node (so you connect without a password) and a key in your cluster home directory that the compute-node sshd will use as its host key. Both are covered on Passwordless SSH — follow it to create an ed25519 key pair before continuing.

2. Add an SSH config. On your local machine, add to ~/.ssh/config (replace <username> with your Pitt username):

Host htc
  HostName htc.crc.pitt.edu
  User <username>
  ControlMaster auto
  ControlPath ~/.ssh/master-%r@%h:%p

Host htcx
  ProxyCommand ssh htc 'nc $(squeue --me --name=tunnel --states=R -h -O NodeList,Comment)'
  StrictHostKeyChecking no
  User <username>

Windows

If ControlMaster isn't available on your machine, omit the ControlMaster and ControlPath lines from the Host htc block; the rest is unchanged.

3. Create the tunnel job script. On the cluster, create ~/tunnel.sbatch:

#!/bin/bash
#SBATCH --output="tunnel.log"
#SBATCH --job-name="tunnel"
#SBATCH --time=4:00:00
#SBATCH --cpus-per-task=2
#SBATCH --mem-per-cpu=8G

module load python   # any Python module works (see Discovering Software); used only to find a free port

# find an open port and record it in the job's Comment field
PORT=$(python -c 'import socket; s=socket.socket(); s.bind(("", 0)); print(s.getsockname()[1]); s.close()')
scontrol update JobId="$SLURM_JOB_ID" Comment="$PORT"

# start an sshd on that port, using your key as the host key
echo "Starting sshd on port $PORT"
/usr/sbin/sshd -D -p ${PORT} -f /dev/null -h ${HOME}/.ssh/id_ed25519

Connecting (each time)

From your local terminal, ssh htc, then start the tunnel job:

[user@login1 ~]$ sbatch tunnel.sbatch
Submitted batch job 1383495
[user@login1 ~]$ squeue -u $USER
  JOBID  PARTITION    NAME   USER  ST   TIME  NODES  NODELIST(REASON)
1383495        htc  tunnel   user   R   0:17      1  htc-1024-n0

Once the job is running, open VS Code locally and connect via Remote Explorer using htcx as the SSH target.

Requesting a GPU

Add a gpux host to your local ~/.ssh/config:

Host gpux
  ProxyCommand ssh htc 'nc $(squeue -M gpu --me --name=tunnel --states=R -h -O NodeList,Comment)'
  StrictHostKeyChecking no
  User <username>

And change the #SBATCH lines in ~/tunnel.sbatch to target the GPU cluster:

#SBATCH --time=0-01:00:00
#SBATCH --cpus-per-task=2
#SBATCH --cluster=gpu
#SBATCH --partition=a100      # a100 | l40s | h200 | ... (see the GPU hardware page)
#SBATCH --gres=gpu:1

Then connect using gpux as the SSH target instead of htcx. See the GPU cluster page for available partitions.

Related

• Browser access

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  Code Server, VNC, and other apps through Open OnDemand.

  Open OnDemand

• Set up SSH keys

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  Passwordless SSH, required for the remote tunnel.

  Passwordless SSH

• Interactive sessions

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  Other ways to get a shell on a compute node.

  Interactive Jobs

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