How to install Dropbear SSH on Centos and Ubuntu

Table of Contents

Introductions

SSH (Secure Shell) is a network protocol to secure connection between client and server. Most SSH servers are using OpenSSH by default, Here we will show you how to install a lightweight SSH server, called Dropbear for the low resource server.

Requirements

centos 6.x 64 bit (or higher) / ubuntu 16.04 64 bit (or higher)

Starting the Installation

Connect to the SSH Servers (default port 22) and make sure you are up to date
Centos

yum update -y

Ubuntu

apt-get update -y

install Dropbear
Centos

yum install epel-release -y
yum install dropbear -y

Ubuntu

apt-get install dropbear -y

small configuration to specify which port to open
Centos

nano /etc/sysconfig/dropbear

then write this configuration to open port 443, 80 and enable the login banner from /etc/issue.net file

KEYGEN=/usr/bin/dropbearkey
DROPBEAR=/usr/sbin/dropbear
RSA_KEY=/etc/dropbear/dropbear_rsa_host_key
DSS_KEY=/etc/dropbear/dropbear_dss_host_key
ECDSA_KEY=/etc/dropbear/dropbear_ecdsa_host_key
PID_FILE=/var/run/dropbear.pid
OPTIONS="-p 443 -p 80 -b /etc/issue.net"

Ubuntu

nano /etc/default/dropbear

Then set NO_START to 0 to enable dropbear and you can change the port on DROPBEAR_PORT, this a minimal configuration to open port 80,443 and enable the login-banner

NO_START=0
DROPBEAR_PORT=443
DROPBEAR_EXTRA_ARGS="-p 80"
DROPBEAR_BANNER="/etc/issue.net"
DROPBEAR_RECEIVE_WINDOW=65536

next, you can write something for the login banner, open /etc/issue.net using your favorite editor,
you can use the nano command for the easiest editor but you need to install it first on CENTOS