Forem: gautam-droid

🔑 Setting Up SSH Key-Based Authentication

gautam-droid — Tue, 01 Apr 2025 06:06:04 +0000

Before Proceeding ⏳👉 If you're interested in learning how to retrieve a username and IP, be sure to check out my first post for a detailed explanation! 🔍💡
How to log in to a remote server using SSH with a username and password

1️⃣ Start the SSH Server on the Host Machine

🚀 Run the following command on your host machine to start the SSH server:

sudo systemctl start ssh

🔍 To check the status, run:

sudo systemctl status ssh

2️⃣ Generate an SSH Key on the Client Machine

✅ Before proceeding, check if any key is present in the host machine's .ssh folder:

cd ~/.ssh
ls

If there are any keys present, like id_rsa, id_ed25519, or any other name, choose a different file name unless you want to overwrite it.

💻 Now, on your client machine (yes, you heard it right), generate an SSH key pair by running:

sudo ssh-keygen -b 4096

ℹ️ Note: The -b flag specifies the key length in bits (4096 in this case).

✅ When prompted for the filename, hit enter to use the default location (~/.ssh/id_rsa) if no existing keys are present.

For a passphrase, if you don’t want one, hit Enter ✅🔑

⚠️ If a file already exists in ~/.ssh/, it's recommended to specify a custom filename (don't forget to provide the full path, or it will be created in your current directory):

~/.ssh/customFileName

🎯 Press enter to continue.

3️⃣ Copy the Public Key to the Host Machine

💡 Tip: It doesn't matter where you generate the key. What matters is that the private key should remain on the client machine, and the public key should be on the host machine. If needed, you can also transfer it manually.

📤 To copy the public key to the host machine from the client machine, run:

ssh-copy-id -i ~/.ssh/customFileName.pub username@ip

📌 This command specifies which public key to send to the host machine. In turn, it will be added to ~/.ssh/authorized_keys.

🔄 Alternatively, if you want to automatically pick the default public key from ~/.ssh/, use:

ssh-copy-id username@ip

4️⃣ Verify the Key on the Host Machine (Optional)

🛠️ On your host machine, check if the key was copied successfully:

cat ~/.ssh/authorized_keys

The key in this file should be exactly the same as the public key on your client machine. If there are multiple keys, look for the one that matches your public key.

5️⃣ Log in to the Host Machine from the Client Machine

🔑 Now, try logging into your host machine from the client machine:

ssh username@ip

🔐 The first attempt will still ask for a password.

🎉 On the second attempt, key-based authentication should work.

⚠️ Troubleshooting: Still Asking for Password?

If SSH still prompts for a password after the first attempt:

1️⃣ On your host machine, edit the SSH configuration file:

sudo nvim /etc/ssh/sshd_config

2️⃣ 🔎 Search for the following settings and update them if necessary:

PasswordAuthentication → Change yes to no

Public Key Authentication → Change no to yes

AuthorizedKeysFile → Uncomment this line

3️⃣ 💾 Save and exit (:wq in nvim).

4️⃣ 🔄 Restart the SSH server:

sudo systemctl restart ssh

🎉 You're Done!

✅ Now, you should be able to log in without a password using SSH key-based authentication. 🚀

Thank you all for taking the time to read this post! 🙌
I truly appreciate your support and hope you found it helpful. 🚀

🖥️ HOW TO LOGIN INTO A REMOTE SERVER USING SSH WITH USER LOGIN (USERNAME AND PASSWORD)

gautam-droid — Tue, 01 Apr 2025 05:44:09 +0000

🔹 Step 1: Install Required Packages

📥 Install OpenSSH Server (for self-hosting your Linux distro) or Dropbear (a lightweight SSH server and client).

To install OpenSSH Server:

Debian/Ubuntu:

  sudo apt install openssh-server -y

Arch Linux:

  sudo pacman -S openssh

Fedora:

  sudo dnf install openssh-server

CentOS/RHEL:

  sudo yum install -y openssh-server

🔹 Note: For Dropbear, replace openssh-server with dropbear in the installation commands.

🔹 Step 2: Check SSH Server Status

🛠️ Run the following command to check the status:

If you are using Dropbear:

  sudo systemctl status dropbear

If you are using OpenSSH Server:

  sudo systemctl status ssh

⚡ In the further steps, we will continue with OpenSSH. Everything will be the same for Dropbear.

🔹 Step 3: Start the SSH Server (If Inactive)

🚀 If the status shows inactive, start the server using:

  sudo systemctl start ssh

(Replace "start" with "stop" to stop the server.)

🔹 Step 4: Open a Terminal for Connection

🖥️ Open a new terminal,PuTTY, Termux, or any other terminal to connect to the host computer.

🔹 Step 5: Find the Host's IP and Username

🌐 To get the IP address, run:

  ifconfig

🔍 Search for "inet"—the digits following the colon are the user’s IP(private).

👤 To get the username, run:

  whoami

📌 Note:

If the client and host are on the same network (e.g., same WiFi router), use the local IP to connect.
If the client and host are on different networks (e.g., the host is on home WiFi and the client is on cellular data or different WiFi), use the public IP of the host. Get it by visiting WhatIsMyIP.com on the host machine.
Ensure port forwarding for port 22 on your host machine’s WiFi router to allow the connection.
Ignore port forwarding if on the same network, as you can directly connect using the host machine’s private IP.

Note: My host is connected to a WiFi router, and my client machine (phone) is on a cellular network, so I need to consider my public IP.

🔹 Step 6: Connect to the Remote Server

🔑 Run the following command:

ssh username@ip

🔐 You will be asked for a password to run the sudo command and another password to log into the server.

🔹 Step 7: Log into the Server

💻 Now, connect to the server using the command from Step 6, replacing it with the host’s username and IP, then enter the password.

Type Yes, here!!! ✅🎯

Enter the password and hit Enter 🔑➡️⏎

🔹 Step 8: Verify the SSH Connection

🔍 To check if the connection is active, run:

who

📋 It will show a list of users currently using your distro.
Look for something like /pts/0 or /pts/any_number—if it's present, your session is active, or a user is logged in.

🔹 Step 9: Kill an Active SSH Connection (If Needed)

⚠️ To terminate a particular SSH session, run:

  sudo fuser -k /dev/pts/<the_number>

🔌 This will disconnect the user from the SSH session.

🔹 Step 10: Confirm Disconnection

🔁 Again, check the active connections using the who command.(Look at the above screenshot 👆👆👆)

A message appears showing the connection has been closed 👇👇👇

🔹 Step 11: Logout or Stop the SSH Server

🔓 To log out, type:

  exit

Successfully exited!! ✅🚪

⛔ To stop the SSH server, run the command listed in Step 2.

Thanks for reading! 🎉 You've now set up an SSH server, connected remotely, and managed your sessions. Stay secure by using SSH keys (more on that in my next post—stay tuned!), disabling root login, and using firewalls or VPNs.

If connecting over the internet, be mindful of your public IP, enable port forwarding, and use strong passwords or SSH keys.

Got questions? Drop a comment! Don't forget to follow for more tech guides. Happy SSH-ing! 🚀🔑