This tutorial will help you to install and secure the OpenSSH server on Pop!_OS Linux. In this tutorial, we will cover the following topics:

1. Installing OpenSSH server on Pop!_OS
2. Configuring the OpenSSH server
3. Using the OpenSSH client to connect to a remote system
4. Securing the OpenSSH server

Step 1: Installing OpenSSH Server on Pop!_OS

The OpenSSH server packages are available under the default system repositories. You first need to update the package manager cache by running the following command:

sudo apt update 

Next, install the OpenSSH server by the below-mentioned command:

sudo apt install openssh-server 

Press ‘y’ when prompted for confirmation. This will install the OpenSSH server and all the necessary dependencies.

Once the installation is complete, the OpenSSH server will be automatically started and enabled to start on boot. You can check the service status by running the ‘systemctl status ssh’ command.

Step 2: Configuring the OpenSSH Server:

Once the OpenSSH server is installed, you can configure it by editing the main configuration file, which is located at “/etc/ssh/sshd_config“. This file contains a number of options that control the behavior of the OpenSSH server.

Some of the most important options that you might want to configure include:

• Port: This option specifies the port number that the OpenSSH server listens on. By default, the OpenSSH server listens on port 22, but you can change this to any unused port number if you want to.

  Port 22

• PermitRootLogin: This option controls whether root login is allowed over SSH. By default, root login is disabled, but you can enable it by setting this option to “yes”.

  PermitRootLogin yes

• PubkeyAuthentication: This option controls whether public key authentication is allowed. By default, public key authentication is enabled, but you can disable it by setting this option to “no”.

  PubkeyAuthentication yes

• PasswordAuthentication: This option controls whether password authentication is allowed. By default, password authentication is enabled, but you can disable it by setting this option to “no”.

  PasswordAuthentication no

Once you have edited the OpenSSH server configuration file, you need to restart the OpenSSH server to apply the changes. You can do this by running the following command:

sudo systemctl restart ssh 

Step 3: Using the OpenSSH Client to Connect to a Remote System:

To connect to a remote system using OpenSSH, you will need to use the OpenSSH client, which is included in most Linux distributions. To connect to a remote system, you need to know the IP address or hostname of the system, as well as the username and password of a user account on the remote system.

To connect to a remote system, open a terminal and enter the following command:

# Syntax
ssh username@remote_system

Replace “username” with the username of the user account on the remote system, and “remote_system” with the IP address or hostname of the remote system. For example, to connect to a remote system with the IP address 192.168.1.100 as the user “user1”, you would enter the following command:

ssh user1@192.168.1.100 

If this is the first time you are connecting to the remote system, you will be prompted to confirm the authenticity of the host. Type “yes” to continue. You will then be prompted to enter the password for the user account on the remote system. Once you have entered the correct password, you will be logged in to the remote system.

Step 4: Securing the OpenSSH Server:

To secure the OpenSSH server, there are several steps you can take:

• Use strong passwords: Make sure that all user accounts on the OpenSSH server have strong, unique passwords. Avoid using easy-to-guess passwords, and use a combination of letters, numbers, and special characters.
• Use public key authentication: Instead of using passwords for authentication, consider using public key authentication. With public key authentication, you generate a public and private key pair, and the public key is copied to the remote system. When you connect to the remote system, you use the private key to authenticate, instead of a password. This is more secure than password authentication, as the private key is much harder to guess than a password.
• Limit access to specific users: Instead of allowing any user to connect to the OpenSSH server, consider limiting access to specific users. You can do this by adding the names of the allowed users to the “AllowUsers” option in the OpenSSH server configuration file.
• Limit access to specific IP addresses: If you only want to allow connections from specific IP addresses, you can use the “AllowUsers” and “DenyUsers” options to specify which users are allowed to connect from which IP addresses.
• Use a firewall: Use a firewall to block access to the OpenSSH server from unwanted IP addresses. You can use the FirewallD service on Pop!_OS to set up a firewall and allow connections only from specific IP addresses.

Conclusion

In summary, OpenSSH is a powerful and flexible tool for securely accessing and managing remote systems. By following the steps outlined in this article, you can install and configure the OpenSSH server on Pop!_OS, use the OpenSSH client to connect to a remote system, and secure the OpenSSH server to protect against unauthorized access.

The post How to Install and Secure OpenSSH Server on Pop!_OS appeared first on TecAdmin.

Features of OpenSSH

• Open Source Project
• Free Licensing
• Strong Encryption (3DES, Blowfish, AES, Arcfour)
• X11 Forwarding (encrypt X Window System traffic)
• Port Forwarding (encrypted channels for legacy protocols)
• Strong Authentication (Public Key, One-Time Password and Kerberos Authentication)
• Agent Forwarding (Single-Sign-On)
• Data Compression

Click here to know more details about OpenSSH features.

Step 1 – Install/Update OpenSSH Server

OpenSSH Server packages is available under default apt repositories under all versions of operating systems. You can install or update latest OpenSSH server using following command.

sudo apt-get update
sudo apt-get install openssh-server

Step 2 – Start/Stop OpenSSH Service

After installing OpenSSH latest packages from default apt repository. You OpenSSH server will start automatically. But if you need to Start, Stop or Restart OpenSSH server from the command line, use the following commands

sudo service ssh start
sudo service ssh stop
sudo service ssh restart

Step 3 – Open Firewall Port

If you are using iptables to secure your server, use following command to open port for SSH access.

sudo iptables -A INPUT -s 192.168.1.0/24 -p tcp --dport 22 -j ACCEPT

Or if you are using ufw for managing firewall use following command.

sudo ufw allow from 192.168.1.0/24 to any port 22

What Next: 5 Tips to secure openssh-server

The post How to Install or Update OpenSSH Server on Ubuntu & LinuxMint appeared first on TecAdmin.

OpenSSH is the most widely used ssh server for Linux-based systems. This article describes how to install the OpenSSH server on Debian Linux systems. OpenSSH is used to connect securely to the server from remote ssh client systems.

Step 1 – Installing OpenSSH Server on Debian

OpenSSH server can be installed on Debian systems using the default Apt repositories. You can update Apt-cache and install OpenSSH using the following commands. If OpenSSH is already installed, it will be upgraded to the latest version.

sudo apt update 
sudo apt install openssh-server 

Step 2 – Secure OpenSSH Server

The /etc/ssh/sshd_config is the main configuration file for OpenSSH server. After successfully installing the OpenSSH server on your system, you may need to make few changes to secure your server.

• Change Default Port – OpenSSH runs on default port 22. We recommend changing the SSH port to another port.

  Port 2222
  

• Disable Root Login – By default root user are allowed to ssh from remote clients, For security purpose we recommend to disable direct root access. Use any non-root account for ssh and then switch ( su – ) to the root account. To do this add “PermitRootLogin no” in ssh configuration file

  PermitRootLogin no
  

Remember to restart the OpenSSH server after making changes to the configuration files.

For more details visit https://tecadmin.net/5-tips-to-secure-openssh-server/

Step 3 – Manage OpenSSH Service

Systemd is the default service manager for the latest Debian operating systems. You can manage the OpenSSH service state usign the systemctl command.

Use one of the below commands to start, stop, or restart the OpenSSH service:

sudo systemctl restart ssh 
sudo systemctl start ssh 
sudo systemctl stop ssh 

To check the current status, type:

sudo systemctl status ssh 

Conclusion

The procedure for installing or upgrading the OpenSSH server on Debian Linux is described in this tutorial. You also learn how to change the default SSH port and disable root login.

The post A Guide to Install or Update OpenSSH Server on Debian. appeared first on TecAdmin.