SSH (Secure Shell) is a widely used protocol that enables secure, encrypted remote access to Linux systems. This guide explains how to install and configure the OpenSSH server across different Linux distributions.
Understanding SSH
SSH provides secure command-line access, file transfers, and remote command execution while protecting against unauthorized access. Most Linux distributions include the OpenSSH client by default, but the server component may require manual installation.
Client vs. Server
- OpenSSH Client: Connects securely to remote systems, enabling command-line access and file transfers.
- OpenSSH Server: Hosts SSH connections, allowing remote users to access and control the system securely.
SSH Requirements
Target Machine (system you want to connect to):
- OpenSSH Server installed
- SSH daemon (sshd) running
- Port 22 open (or custom SSH port)
Source Machine (system you connect from):
- OpenSSH Client installed
- Used to initiate connections
- Most Linux distributions include SSH client by default
Installation Instructions
Debian-based distributions
Target Machine:
sudo apt install openssh-server
Source Machine:
sudo apt install openssh-client
Red Hat-based distributions
Target Machine:
sudo dnf install openssh-server
Source Machine:
sudo dnf install openssh-clients
Arch-based distributions
Target Machine:
sudo pacman -S openssh
Source Machine:
sudo pacman -S openssh
openSUSE-based distributions
Target Machine:
sudo zypper install openssh
Source Machine:
sudo zypper install openssh-clients
Post-Installation Steps (Target Machine)
Start SSH Service
Debian-based:
sudo systemctl start ssh
Red Hat, Arch, openSUSE:
sudo systemctl start sshd
Enable at Boot
Debian-based:
sudo systemctl enable ssh
Red Hat, Arch, openSUSE:
sudo systemctl enable sshd
Check Status
Debian-based:
sudo systemctl status ssh
Red Hat, Arch, openSUSE:
sudo systemctl status sshd
Note: Debian-based systems name the service ssh, while other distributions use sshd.
Firewall Configuration
Ensure the firewall allows traffic on port 22 (or your custom SSH port) for remote connections.
Basic Usage
From the source machine, connect to the target machine using:
ssh username@target_ip_address
Example:
ssh john@192.168.1.100
Only the target machine requires the SSH server. The source machine only needs the SSH client.
By following these steps, you can install and configure an SSH server on Linux, enabling secure remote access and system management.
With SSH properly set up, you’ll have a reliable and secure way to connect to your Linux systems remotely for administration, development, and file transfers.