To SSH from your Mac to your Linux machine, you’ll need to ensure both machines are set up properly for SSH communication. Here’s a step-by-step guide for setting everything up from scratch:

On Linux (Mini PC):

1. Install SSH Server: If SSH is not already installed on your Linux machine, you’ll need to install the OpenSSH server. To do this:

   1. Open a terminal.
   2. Run the following command:

      sudo apt update
      sudo apt install openssh-server

   3. Once installed, check if the SSH service is running:

      sudo systemctl status ssh

   4. If SSH is not running, start the service:

      sudo systemctl start ssh

   5. Ensure the service starts on boot:

      sudo systemctl enable ssh

2. Check Your Linux Machine’s IP Address: You’ll need the IP address of the Linux machine to connect from your Mac. To find it:

   1. Open a terminal.
   2. Run the following command:

      ip a

   3. Look for the section related to your active network interface (e.g., eth0 for wired or wlan0 for Wi-Fi) and find the IP address (something like 192.168.x.x).

On Mac:

1. Install OpenSSH (if not already installed): Most modern macOS systems come with OpenSSH pre-installed, but you can check if it's installed by running:

   ssh -V

   If it shows a version, you’re good to go. If not, you may need to install it using Homebrew:

   1. Install Homebrew (if you don’t have it):

      /bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"

   2. Install OpenSSH:

      brew install openssh

2. Connect to the Linux Machine:

   1. Open a terminal on your Mac.
   2. Use the SSH command to connect to your Linux machine (replace user with your Linux username and 192.168.x.x with the Linux machine’s IP):

      ssh user@192.168.x.x

   3. The first time you connect, you may be prompted to accept the server’s fingerprint. Type yes and hit Enter.
   4. Enter your Linux user password when prompted.

3. Configure SSH Key-Based Authentication (Optional but recommended): To avoid entering the password each time, you can set up SSH keys:

   1. On your Mac, generate an SSH key (if you don’t have one already):

      ssh-keygen -t rsa

      Press Enter to save the key in the default location (~/.ssh/id_rsa).
   2. Copy the SSH public key to your Linux machine:

      ssh-copy-id user@192.168.x.x

   3. Now, when you SSH, you should be able to connect without needing a password:

      ssh user@192.168.x.x

Troubleshooting:

• Ensure both machines are on the same network.
• If the connection fails, check the firewall settings on your Linux machine:

  sudo ufw allow ssh
  sudo ufw enable

Details on Public Key Copy from host to remote

After generating the SSH key on your Mac, you need to copy the public key to your Linux machine. This allows you to log into the Linux machine without entering a password each time, enabling key-based authentication. Below are the detailed steps:

1. Generate the SSH Key on Your Mac (if you haven’t done it already)

If you haven’t generated an SSH key, do it with the following command:

ssh-keygen -t rsa

• Explanation:
  • -t rsa specifies the type of key (RSA in this case).
• You will be prompted to enter a location to save the key. Press Enter to save it in the default location: ~/.ssh/id_rsa.
• You may also be asked to provide a passphrase for extra security. If you don't want a passphrase, just press Enter to leave it blank.

2. View the Generated Public Key

You’ll now have two files in the ~/.ssh/ directory:

• id_rsa (your private key)
• id_rsa.pub (your public key)

To confirm the public key, you can view it with:

cat ~/.ssh/id_rsa.pub

3. Copy the SSH Key to Your Linux Machine

The next step is to copy the public key to your Linux machine. This is where the ssh-copy-id command is used.

1. Make sure SSH is running on your Linux machine and you have its IP address and username ready.

   • You can check the SSH service with:

     sudo systemctl status ssh

2. Copy the Public Key to the Linux machine:

   In your Mac terminal, run the following command (replacing user with your Linux username and 192.168.x.x with your Linux machine’s IP address):

   ssh-copy-id user@192.168.x.x

   • Explanation:
     • ssh-copy-id is a convenient command that copies your public key to the Linux machine's ~/.ssh/authorized_keys file, which is used for authentication.
     • user@192.168.x.x is the Linux username and IP address you want to log in to.

3. Authenticate with Your Password:

   • You will be asked to enter the password for the Linux user account you are copying the SSH key to. This is necessary just for the first time to authorize the key copy.
   • Once the password is entered, ssh-copy-id will automatically add your public key to the Linux machine’s ~/.ssh/authorized_keys file.

4. Verify SSH Key-Based Authentication

Now that the public key has been copied to the Linux machine, you can log in without needing a password.

1. From your Mac, try SSHing into the Linux machine again:

   ssh user@192.168.x.x

2. This time, you should be logged in without being prompted for a password.

5. (Optional) Disable Password Authentication on the Linux Machine

For extra security, you may want to disable password-based SSH logins, ensuring only SSH keys can be used.

1. On the Linux machine, open the SSH configuration file for editing:

   sudo nano /etc/ssh/sshd_config

2. Find the following lines (uncomment them if needed) and change the values:

   PasswordAuthentication no
   PermitRootLogin no

   This disables password logins and root login via SSH.

3. Restart the SSH service:

   sudo systemctl restart ssh

Now, only key-based logins will be allowed, adding an extra layer of security.

Troubleshooting

• Permission issues: Ensure the ~/.ssh/authorized_keys file on the Linux machine has the correct permissions. Use:

  chmod 600 ~/.ssh/authorized_keys

• Firewall: If you're unable to connect, ensure that the firewall on the Linux machine allows SSH:

  sudo ufw allow ssh

That’s it! You’ve now set up passwordless SSH login using key-based authentication.

Using NetworkManager to manage network connections

It is best to assign a static IP through NetworkManager directly rather than manually editing Netplan files.

Here's how you can assign a static IP using NetworkManager:

Method 1: Using nmtui (Text User Interface)

1. Open the Terminal on your Linux machine.

2. Launch NetworkManager Text User Interface:

   sudo nmtui

3. Select "Edit a connection":

   • Use the arrow keys to highlight this option and press Enter.

4. Choose Your Wi-Fi Network:

   • You should see a list of available network connections (your wlp3s0 Wi-Fi interface should be listed). Highlight your Wi-Fi connection and press Enter.

5. Set Static IP Address:

   • In the Edit Connection window:
     • Set the IPv4 Configuration method to Manual.
     • Enter the following details:
       • Addresses: The static IP you want to use (e.g., 192.168.1.100).
       • Netmask: Usually 255.255.255.0.
       • Gateway: The IP address of your router (e.g., 192.168.1.1).
       • DNS servers: For example, you can use Google's DNS (8.8.8.8).

6. Save the Configuration:

   • Once you've entered the IP details, move to OK using the arrow keys and press Enter.

7. Restart the Network: After saving the settings, you can restart the NetworkManager service to apply the changes:

   sudo systemctl restart NetworkManager

8. Verify Your IP Address: Check if the static IP has been assigned by running:

   ip a

Method 2: Using nmcli (Command Line Interface)

If you prefer to work entirely in the command line, you can use the nmcli command to set a static IP address.

1. Check Your Wi-Fi Connection Name: Run the following command to list all available network connections:

   nmcli connection show

   • Look for the NAME of your Wi-Fi connection (likely something like wlp3s0).

2. Set Static IP Address: Replace wlp3s0 with your actual connection name. For example:

   sudo nmcli con modify wlp3s0 ipv4.method manual ipv4.addresses 192.168.1.100/24 ipv4.gateway 192.168.1.1 ipv4.dns 8.8.8.8

   • 192.168.1.100/24: Your desired static IP address and subnet mask.
   • 192.168.1.1: Your router's IP address (gateway).
   • 8.8.8.8: DNS server.

3. Apply the Changes: To bring the connection down and up again to apply the new settings:

   sudo nmcli con down wlp3s0 && sudo nmcli con up wlp3s0

4. Verify Your IP Address: Run the following command to ensure the static IP has been assigned:

   ip a

If everything is configured correctly, your Linux machine should now use a static IP address over Wi-Fi. Let me know if you encounter any issues!

Easy Access to Remote without typing IP everytime

Updating the /etc/hosts file or the SSH config (~/.ssh/config) is useful if you frequently SSH into the same machine. These methods allow you to associate a hostname or a shortcut name with the IP address of your Linux machine, so you don’t need to remember or type the full IP address each time you SSH.

1. Update the /etc/hosts File

The /etc/hosts file allows you to map a hostname (alias) to an IP address. This means you can type the hostname instead of the IP address when you SSH or access the machine.

Steps:

1. Open the Terminal on your Mac.

2. Edit the /etc/hosts file:

   • You will need superuser privileges to edit this file. Run the following command:

     sudo nano /etc/hosts

   • You will be prompted to enter your password.

3. Add the IP Address and Hostname:

   • At the bottom of the file, add a line with the new static IP of your Linux machine followed by a hostname (or alias) you want to use. For example:

     192.168.1.100 linuxpc

   • Replace 192.168.1.100 with the new IP of your Linux machine and linuxpc with any alias you prefer.

4. Save the File:

   • After adding the line, press Ctrl + O to save the file, then press Enter.
   • Press Ctrl + X to exit the editor.

5. Test the Change:

   • Now, instead of using the IP address to SSH into your Linux machine, you can use the alias (hostname) you just set. For example:

     ssh user@linuxpc

   • Replace user with your Linux username and linuxpc with the alias you assigned.

   This way, even if you change the Linux machine's IP again, you can just update the /etc/hosts file with the new IP, and the alias (linuxpc) will still work.

2. Update the SSH Config File (~/.ssh/config)

The SSH config file allows you to create shortcuts for SSH connections, where you can define specific settings for different hosts (like the IP address, username, port, etc.). This is very useful when you frequently SSH into multiple servers.

Steps:

1. Open the Terminal on your Mac.

2. Create/Edit the SSH Config File:

   • The SSH config file is located in the ~/.ssh directory. If it doesn't exist, you can create it. Run the following command to open it for editing:

     nano ~/.ssh/config

3. Add SSH Configuration for Your Linux Machine:

   • Add a new entry with the following format:

     Host linuxpc
         HostName 192.168.1.100
         User your_username
         Port 22

     • Host: This is the alias or shortcut you want to use for SSH. It can be any name you choose (e.g., linuxpc).
     • HostName: The actual IP address or hostname of your Linux machine.
     • User: Your username on the Linux machine (so you don’t need to type it every time).
     • Port: The SSH port (default is 22). If your SSH server is running on a different port, change this value.

4. Save the File:

   • After adding the configuration, press Ctrl + O to save the file, then press Enter.
   • Press Ctrl + X to exit the editor.

5. Set Correct Permissions for the Config File:

   • SSH requires this file to have correct permissions. Run the following command to set the correct permissions:

     chmod 600 ~/.ssh/config

6. Test the Change:

   • Now, you can use the alias to SSH into your Linux machine without typing the full IP and username each time. For example:

     ssh linuxpc

   • This will automatically use the IP (192.168.1.100) and username you specified in the ~/.ssh/config file.

Example of Multiple Hosts in SSH Config:

If you connect to multiple servers, you can add multiple entries in your ~/.ssh/config file, like so:

Host linuxpc
    HostName 192.168.1.100
    User your_username

Host workserver
    HostName 203.0.113.10
    User your_work_username
    Port 2222

• In this example, you can SSH into linuxpc or workserver with simple commands:

  ssh linuxpc
  ssh workserver

Summary:

• Updating /etc/hosts allows you to map a custom hostname (alias) to the IP address, so you can use the alias instead of the IP when connecting via SSH or accessing the machine on the network.
• Updating ~/.ssh/config allows you to create SSH shortcuts and store specific settings like username, IP address, and port, making it easier to SSH into frequently accessed machines.

These methods save you time and prevent you from having to remember or type IP addresses repeatedly.

Save Passphrase to Mac KeyChain for easy access

You can save the passphrase for your SSH key to avoid entering it every time you use the key for authentication. The most common way to achieve this is by using an SSH agent, which stores your passphrase in memory for the duration of your session.

Here’s how you can set this up on macOS:

1. Start the SSH Agent

The SSH agent is usually started by default on macOS, but you can ensure it’s running by starting it manually.

Open your terminal and run:

eval "$(ssh-agent -s)"

This will start the SSH agent and return the process ID (PID), indicating that it's running.

2. Add Your SSH Private Key to the Agent

Once the SSH agent is running, you need to add your private key to it. This allows the agent to cache the key and manage the passphrase for you.

To add your private key:

ssh-add ~/.ssh/id_rsa

• Replace ~/.ssh/id_rsa with the path to your private key if it’s located somewhere else.

You will be prompted to enter your passphrase one last time. After that, the agent will store the passphrase for the duration of your session, so you won’t have to enter it again.

3. Configure SSH to Automatically Use the Agent

To make the SSH agent automatically load your key when the system starts, you can modify or create a configuration file:

1. Open or create the SSH config file:

   nano ~/.ssh/config

2. Add the following lines:

   Host *
       AddKeysToAgent yes
       UseKeychain yes
       IdentityFile ~/.ssh/id_rsa

   • AddKeysToAgent yes: This tells SSH to automatically add keys to the agent.
   • UseKeychain yes: On macOS, this stores the passphrase in the macOS Keychain.
   • IdentityFile ~/.ssh/id_rsa: Specifies the location of your private key. Change the path if your key is located elsewhere.

3. Save and close the file by pressing Ctrl + O to save and Ctrl + X to exit.

4. Store the Passphrase in macOS Keychain

macOS allows you to store your SSH key passphrase in the Keychain, so you don’t need to enter it again after rebooting. You can do this by using the ssh-add command with the -K option (on older macOS versions) or simply by following the steps above (UseKeychain yes).

To store the passphrase in the macOS Keychain:

ssh-add --apple-use-keychain ~/.ssh/id_rsa

• After running this command, the passphrase will be saved to the Keychain, so you won’t need to enter it again for future logins.

On macOS Monterey (12.x) and later, ssh-add automatically uses the Keychain without needing the -K option.

5. Verify SSH Key is Loaded

To check that your key has been successfully added to the agent, run:

ssh-add -l

This will list the keys currently loaded in the SSH agent. You should see your key listed here.

6. Restarting the SSH Agent Automatically

To ensure your keys are automatically loaded into the SSH agent on system startup, you can add the following to your shell’s configuration file (.bash_profile, .zshrc, etc.):

1. Open your shell’s config file: For example, if you are using zsh:

   nano ~/.zshrc

2. Add the following lines:

   eval "$(ssh-agent -s)"
   ssh-add -A

   • ssh-add -A: Automatically adds all identities stored in the macOS Keychain to the SSH agent when a new session is started.

3. Save and close the file.

Now, every time you start a new terminal session or log into your Mac, the SSH agent will automatically start, and your keys will be loaded from the Keychain.

---

By following these steps, you’ll avoid having to enter the passphrase for your SSH key every time you SSH into a machine, without compromising the security of your key.