Fix: SSH Blocked by VS Code? 5 Steps for Ubuntu [2025]

Understanding the Problem: Why Does VS Code Block SSH?

You’ve been there. You open your Ubuntu terminal, type ssh your-user@your-server.com, and you’re in. It’s seamless. But when you try the exact same connection through the Visual Studio Code Remote - SSH extension, you’re met with a frustrating, cryptic error: "Could not establish connection to...", "Permission denied (publickey)", or an endless loading bar. It feels like VS Code itself is blocking the connection, but the reality is often more nuanced.

This common issue rarely stems from VS Code actively blocking SSH. Instead, it's usually caused by a discrepancy between the SSH environment of your system's terminal and the one VS Code's extension uses. These differences can arise from:

• Different SSH Configurations: VS Code might not be reading your custom ~/.ssh/config file correctly or at all.
• SSH Agent Issues: The extension may not have access to the SSH agent that has your keys loaded.
• Firewall Rules: A server-side or even client-side firewall might be scrutinizing the specific way VS Code initiates its connection.
• Path and Environment Variables: VS Code's integrated terminal can sometimes have a different $PATH than your default shell, leading it to use a different SSH executable.
• Extension-Specific Bugs: Though less common, an outdated or buggy Remote - SSH extension can be the culprit.

In this guide, we'll walk through a systematic, 5-step process designed for Ubuntu users in 2025 to diagnose and resolve this issue for good.

The 5-Step Fix for SSH Issues in VS Code on Ubuntu

Follow these steps in order. Often, the problem is solved in the first couple of steps, but a systematic approach guarantees you'll find the root cause.

Step 1: Verify Your Baseline SSH Connection

Before diving into VS Code's settings, we must confirm that your fundamental SSH connection is solid from the command line. This isolates the problem to the VS Code environment.

Open a standard Ubuntu terminal (not the one inside VS Code) and run your SSH command with the verbose flag (-v):

ssh -v your-user@your-server.com

This command will print out a detailed log of the connection process. Look for lines that say Authentication succeeded. If you can connect successfully here, you can be 100% certain the issue lies within VS Code's configuration or execution. If this command fails, your problem is with your general SSH setup (keys, server permissions, etc.), and you should fix that before proceeding.

Step 2: Decode the VS Code Remote-SSH Output Log

VS Code provides its own detailed output log for the Remote - SSH extension, which is the most crucial tool for debugging. Don't ignore it!

1. In VS Code, open the Command Palette (Ctrl+Shift+P).
2. Type View: Show Output and press Enter.
3. In the Output panel's dropdown menu (usually on the right), select Remote - SSH.

Now, try to connect to your remote host again. The panel will fill with logs. Scrutinize this output. It will often point directly to the problem. For example, you might see it trying to use the wrong username, a non-existent identity file (key), or failing at a specific stage of the handshake. This log tells you exactly what VS Code thinks it should be doing.

Step 3: Audit Your SSH Configuration File (`~/.ssh/config`)

This is the most common point of failure. The VS Code extension heavily relies on the ~/.ssh/config file to understand how to connect to your hosts. A misconfigured or incomplete entry is a frequent culprit.

Open the file with your favorite editor: nano ~/.ssh/config

Ensure your host entry is correct and explicit. A robust configuration looks like this:

Host my-remote-server
    HostName 192.168.1.100 # or your-server.com
    User myuser
    Port 22 # Change if you use a non-standard port
    IdentityFile ~/.ssh/id_rsa_server_specific # Be explicit!
    IdentitiesOnly yes

Key directives to check:

• Host: This is the alias you use in VS Code to connect.
• HostName: The actual IP address or domain name of the server.
• User: The username for the remote server.
• IdentityFile: This is critical. Explicitly point to the private key file for this specific server. Don't assume VS Code will find the default id_rsa if you use multiple keys.
• IdentitiesOnly yes: A very useful directive that forces SSH to only use the key specified in IdentityFile, preventing it from trying other keys and failing.

After saving your changes, go to the "Remote Explorer" in VS Code and click the refresh button. It will re-read your config file. Try connecting again.

Step 4: Investigate Firewalls on Client and Server

Even if terminal SSH works, a firewall might be configured to be extra strict about the type or pattern of connections. On your Ubuntu server, check the status of the Uncomplicated Firewall (UFW).

Connect to your server via the terminal and run:

sudo ufw status

You should see an entry allowing SSH traffic. It will look like 22/tcp (ALLOW) Anywhere or simply OpenSSH (ALLOW) Anywhere. If it's not there, or if the firewall is inactive, you can allow SSH with:

sudo ufw allow ssh
sudo ufw enable # Only if it was disabled

Also, consider cloud firewalls. If your server is on AWS, GCP, or Azure, check the Security Group or VPC Firewall Rules. Ensure that the inbound rule for port 22 allows traffic from your IP address.

Step 5: Address Advanced Issues & Common Pitfalls

If you're still stuck, the issue might be more subtle. Here are a few final checkpoints:

• File Permissions: SSH is very picky about security. Incorrect permissions on your local machine can cause authentication to fail. Run these commands on your local Ubuntu machine:
  chmod 700 ~/.ssh
chmod 600 ~/.ssh/config
chmod 600 ~/.ssh/id_rsa*
  On the server, ensure your ~/.ssh/authorized_keys file has 600 permissions.
• SSH Agent Forwarding: Sometimes VS Code struggles to communicate with the SSH agent. You can manually add your key to the agent before trying to connect.
  eval $(ssh-agent -s)
ssh-add ~/.ssh/your_private_key
  Then attempt the connection from VS Code.
• Update Everything: Make sure VS Code, the Remote - SSH extension, and your Ubuntu system packages (sudo apt update && sudo apt upgrade) are all up to date. A bug may have been fixed in a recent release.
• Check Server's `sshd_config`: On the remote server, inspect the SSH daemon's configuration file at /etc/ssh/sshd_config. Look for restrictive directives like AllowUsers or DenyUsers that might not include your user, or ensure PubkeyAuthentication yes is set.

Conclusion: Unblocked and Back to Coding

Navigating SSH connection issues within VS Code on Ubuntu can be a detour from your development workflow, but it's a solvable one. By systematically working through these five steps—from verifying the baseline connection to auditing your configurations and checking firewall rules—you can pinpoint the exact cause of the failure. The key is to understand that VS Code relies on a standard SSH foundation, and any discrepancy in that foundation can cause a breakdown. With a corrected configuration and a clear understanding of the troubleshooting process, you can ensure reliable, secure access to your remote environments and get back to what you do best: building great software.