Ubuntu 23.10 Failed to start ssh.service - OpenBSD Secure Shell Server

Question: How do you solve "Ubuntu 23.10 Failed to start ssh.service - OpenBSD Secure Shell Server" error?

Login to See the Rest of the Answer

Answer: This means that the Host has changed IP address hashed into the ssh Keys. In order to resolve this issue, you need to reginerate the ssh private keys on the server by issueing this command.

sudo/usr/bin/ssh-keygen -A

Ubuntu 23.10 Failed to start ssh.service - OpenBSD Secure Shell Server

Edited Version 2

Title
Troubleshooting SSH Service Failure in Ubuntu 23.10
A Comprehensive Guide

Introduction

The OpenSSH server, which provides secure remote access to your Ubuntu system using the Secure Shell (SSH) protocol, is an essential component of any Linux distribution. However, sometimes you might encounter issues starting the SSH service in Ubuntu, preventing you from accessing your system remotely. In this blog post, we will explore the common causes of SSH service failure in Ubuntu 23.10 and provide you with practical solutions to help you get your SSH server up and running again.

Understanding SSH Service Failure

When you encounter an error while starting the SSH service in Ubuntu, you will typically see an error message similar to the following


sudo systemctl status ssh.service
? ssh.service - OpenSSH SSH Daemon
     Loaded
 loaded (/lib/systemd/system/ssh.service; enabled; vendor preset
 enabled)
     Active
 failed (Result
 Exited) since Sun 2023-03-11 15
45
34 EDT; 15s ago
       Docs
 man
sshd(8)
             man
sshd_config(5)
             man
ssh-keys(5)
Mar 11 15
45
34 ubuntu systemd[1]
 Starting OpenSSH SSH Daemon...
Mar 11 15
45
34 ubuntu sshd[14567]
 error
 bind
 Address already in use 127.0.0.1
22
Mar 11 15
45
34 ubuntu systemd[1]
 ssh.service
 Control process exited, code=exited status=1Mar 11 15
45
34 ubuntu systemd[1]
 Failed to start OpenSSH SSH Daemon.

This error message indicates that there is already an SSH server running on your system on port 22, which is preventing the new instance from starting. Let's explore some common causes of this issue and how to resolve them.

Cause #1
SSH Server Already Running

The most common cause of SSH service failure is an already-running SSH server. To check if this is the case, you can use the following command


sudo netstat -tulpn | grep 
22

This command will display all processes listening on port 22. If you see an output similar to the following, then another SSH server is already running


tcp        0      0 127.0.0.1
22              0.0.0.0
*               LISTEN     14567/sshd

To stop the existing SSH server and allow the new one to start, use the following command

sudo systemctl stop ssh.service

sudo systemctl start ssh.service

Cause #2
Firewall Rules

Another common cause of SSH service failure is firewall rules that block incoming SSH connections. To check if this is the issue, you can use the following command to check the status of your firewall