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SSH Server with Rift

Run an SSH server on a GPU-enabled machine managed by CloudRift and learn how to:

  • Start an Ubuntu container and access its bash shell.
  • Install and configure an SSH server within the container.
  • Connect to the SSH server remotely.

Pull and Run the Ubuntu Image​

Once you have rented a GPU and installed CloudRift CLI, run the following Docker command to pull and start the Ubuntu container:

rift docker run --rm -p='2222:22' -it ubuntu /bin/bash

The rift docker run command will automatically select the executor (machine) in your rift cluster and start the Ubuntu container. If you have multiple executors in your cluster, you can specify the executor using -x <executor-name> command line parameter. Names of the executors in your cluster can be found by running rift cluster info.

Here's what this command does:

  • rift docker run: Pulls the Docker image and starts the container.
  • --rm: Automatically removes the container when it exits.
  • -p='2222:22': Maps port 2222 on your server to port 22 on the container, allowing SSH access.
  • -it: Runs the container in interactive mode with a pseudo-TTY.
  • ubuntu: Specifies the Docker image to be run (latest Ubuntu image).
  • /bin/bash: Starts a bash shell in the container.

After running this command, you'll be in the container's bash shell.

caution

If you need to close the terminal window, but you want your container to keep running, press Ctrl-P followed by Ctrl-Q. This will detach the terminal from the container.

If you press Ctrl-C or Ctrl-D, the container will stop. Also, you can specify -d flag instead of -it to run the container in the background when launching it.

Set Up the SSH Server​

Now that you're in the container's bash shell, set up the SSH server:

  1. Update the package list and install OpenSSH server:

    apt-get update && apt-get install -y openssh-server

  2. Set a password for the root user:

    passwd root

  3. Configure SSH to allow root login:

    sed -i 's/#PermitRootLogin prohibit-password/PermitRootLogin yes/' /etc/ssh/sshd_config

  4. Start the SSH service:

    service ssh start

Connect to the SSH Server​

To connect to your SSH server, you'll need the IP address of the executor. You can find this by running:

rift cluster info

Connect to the SSH server using:

ssh -p 2222 root@<executor-ip-address>

Replace <executor-ip-address> with the IP address from the previous step.

Configuring SSH Access with Public/Private Keys​

For improved security and convenience, you can set up SSH access using public/private key pairs instead of password authentication.

  1. On your local machine, generate an SSH key pair if you don't already have one:

    ssh-keygen -t rsa -b 4096

  2. Copy the contents of your public key (usually located at ~/.ssh/id_rsa.pub):

    cat ~/.ssh/id_rsa.pub

  3. In the SSH server container, create the .ssh directory and authorized_keys file:

    mkdir -p /root/.ssh
    touch /root/.ssh/authorized_keys
    chmod 700 /root/.ssh
    chmod 600 /root/.ssh/authorized_keys

  4. Add your public key to the authorized_keys file:

    echo "your_public_key_here" >> /root/.ssh/authorized_keys

    Replace your_public_key_here with the content you copied in step 2.

  5. Modify the SSH configuration to disable password authentication:

    sed -i 's/#PasswordAuthentication yes/PasswordAuthentication no/' /etc/ssh/sshd_config

  6. Restart the SSH service:

    service ssh restart

Now you can connect to your SSH server using your private key:

ssh -p 2222 -i /path/to/your/private_key root@<executor-ip-address>

This method is more secure as it doesn't rely on password authentication, and it's more convenient as you don't need to enter a password each time you connect.

caution

Make sure to keep your private key secure and never share it. If you lose access to your private key, you won't be able to connect to the server without resetting the authentication method.

Remember to stop the container when you're done to avoid unnecessary charges.