Setting static IP and Connect to Ubuntu Linux VM via SSH form host OS with Key-Based Authentication.

Assign a static IP address in Ubuntu 24.04 Linux inside VMware

Check your network

ip a

Backup the file (just in case):

sudo cp /etc/netplan/50-cloud-init.yaml /etc/netplan/50-cloud-init.yaml.bak

Set a Static IP in Ubuntu

Now edit your Ubuntu Netplan config:

sudo nano /etc/netplan/50-cloud-init.yaml

network:
  version: 2
  renderer: networkd
  ethernets:
    ens33:
      dhcp4: no
      addresses:
        - 172.16.25.150/24
      routes:
        - to: default
          via: 172.16.25.2
      nameservers:
        addresses:
          - 8.8.8.8
          - 1.1.1.1

Then apply:

sudo netplan apply

Verify

ip addr show ens33
ip route
ping 8.8.8.8
ping google.com

Connect to your Linux Virtual Machine (VM) terminal from an host via SSH.

output

Understand What SSH Is

SSH (Secure SHell) is a protocol used to securely log into another computer over a network. It encrypts all communication between two systems.

Check If SSH Server Is Installed on Linux VM

Most Linux distributions do not install the SSH server by default for security reasons.

To check if openssh-server is installed:

sudo systemctl status ssh

If you get something like “active (running)”, then SSH is already installed and running.

If not:

Install OpenSSH Server

For Ubuntu/Debian-based distros:

sudo apt install ssh

After installing, start the SSH service:

sudo systemctl start ssh

Enable it to start automatically on boot:

sudo systemctl enable ssh

Configure VM Firewall (UFW/firewalld):

UFW (Uncomplicated Firewall) in Linux is a user-friendly command-line tool designed to simplify the management of firewall rules. It acts as a frontend for the more complex iptables firewall system, making it easier for users to allow or block network traffic on their Linux systems, particularly Ubuntu and Debian-based distributions.

Ensure the VM’s internal firewall allows incoming SSH connections (default port 22).

Now, install the ufw package. (Ubuntu/Debian):

sudo apt install ufw

sudo ufw allow ssh  # This allows port 22/tcp OR sudo ufw allow 22/tcp 
sudo ufw enable         # If not already enabled
sudo ufw status verbose # helps to provide a richer and more detailed description of their operation.

Find the IP Address of the Linux VM

ip a
# OR
ifconfig # if net-tools is installed

Connect to the VM Using SSH From Host Machine

Now open a terminal on your host machine (your main OS), and type:

ssh [email protected]

Then press Enter and type the password when prompted.

If successful, you’ll now be inside the Linux VM’s terminal — but connected via SSH!

Set up SSH key-based authentication.

This method is more secure than using passwords and allows you to log in without typing a password every time.

What Is SSH Key-Based Authentication?

SSH keys are a pair of cryptographic keys:

Private Key: You keep this on your local machine (host), and it must be kept secret.
Public Key: You copy this to the server (your Linux VM). It’s safe to share.

When you connect via SSH, the system checks if your private key matches the public key on the server.

Guide to Set Up SSH Keys

We’ll do this from your host machine and then copy the public key to your Linux VM.

Generate an SSH Key Pair on Your Host Machine

Open a terminal on your host machine (not the VM).

Type:

ssh-keygen -t rsa -b 4096

This command generates a strong RSA key pair with 4096 bits.

Then it asks:

Enter passphrase (empty for no passphrase):

You can leave it empty or set a passphrase for extra security.

Done! Your keys are now created:

Private key: ~/.ssh/id_rsa
Public key: ~/.ssh/id_rsa.pub

Copy the Public Key to Your Linux VM

There are two common ways to do this:

🔹 Option A: Use `ssh-copy-id` (Recommended)

Run this on your host machine:

sudo ssh-copy-id -i ~/.ssh/id_rsa.pub [email protected]

Replace:

username with your Linux VM username.
vm-ip-address with the IP of your VM.

If successful, you’ll see:

Number of key(s) added: 1

🔹 Option B: Manually Copy the Key (if `ssh-copy-id` not available)

On your host machine, view your public key:

cat ~/.ssh/id_rsa.pub

Now, log in to your Linux VM normally via SSH:

ssh [email protected]

Once inside, create the .ssh directory and edit the authorized_keys file:

mkdir -p ~/.ssh
chmod 700 ~/.ssh
nano ~/.ssh/authorized_keys

Paste the public key into the file and save it (Ctrl+O, Enter, Ctrl+X in nano).

Set correct permissions:

chmod 600 ~/.ssh/authorized_keys

Test SSH Without Password

Now try logging in again:

ssh [email protected]

If everything went well, you should be logged in without being asked for a password!

Based on your ip a output, your primary network interface is ens33. To set a static IP, you’ll need to edit the network configuration file and specify the new static details for this interface.

How to Set a Static IP on Debian

Identify the Network Interface: From your output, the interface with a dynamic IP is ens33. You can see its current dynamic IP is 192.168.193.128.
Edit the Network Configuration File: Open the /etc/network/interfaces file using a text editor like nano with administrative privileges.
```
sudo nano /etc/network/interfaces
```
Add Static IP Configuration: Locate the section for ens33 and change it from dhcp (or similar) to static. Add the following lines, replacing the placeholder values with your desired settings.
```
# The primary network interface
auto ens33
iface ens33 inet static
    address 192.168.193.150  # Your new static IP address
    netmask 255.255.255.0
    gateway 192.168.193.1    # Your router's IP address
    dns-nameservers 8.8.8.8 8.8.4.4
```
- address: Choose a static IP within the same subnet as your current IP (192.168.193.x), but outside of your router’s DHCP range to avoid conflicts. For this example, 192.168.193.150 is a good choice.
- netmask: This is typically 255.255.255.0 for home networks.
- gateway: This is your router’s IP address. Based on your current IP, your gateway is likely 192.168.193.1. You can confirm this with the ip route command.
- dns-nameservers: These are the IP addresses of your DNS servers. Google’s public DNS (8.8.8.8) is a reliable option.
Save and Exit: Press Ctrl + X, then Y, and Enter to save the changes and close the editor.
Restart the Network Service: Apply the changes by restarting the networking service.
```
sudo systemctl restart networking
```
Verify the New IP: Run ip a again to confirm that ens33 now shows the static IP address you assigned.