How To Restart SSH Service? (Linux Restart SSHD Server)

SSH, short for Secure Shell, is the most commonly used network protocol facilitating secure communication between computers over potentially insecure networks. This protocol, along with its corresponding tools, enables system administrators and users to remotely access and administer computers with high security. By employing robust encryption techniques and authentication methods like passwords and public keys, SSH ensures that data transmission remains confidential and integrity intact.

SSH operates through a client-server architecture where a Secure Shell client program establishes a secure session with an SSH server. This setup enables users to remotely execute commands, transfer files, and even run graphical sessions securely across networks, including the Internet.

Restarting SSH involves restarting the SSH agent or service responsible for managing SSH connections on a system. This action is often necessary for troubleshooting, security updates, or configuration changes. However, the specific steps to restart SSH may vary depending on the operating system and the configuration of the SSH service.

In this guide, we will demonstrate how to restart an SSH agent or SSH service in different Linux distributions.

Restart SSH Service in Linux (Linux Restart SSHD Server): A Detailed Guide

To restart or reboot SSH service on your system, you'll need to execute a command with root privileges. The specific command varies depending on the Linux distribution or Unix variant you're using.

• To restart SSHD, log in as the root user or a user with sudo privileges.
• Open a terminal or command prompt. Now, enter the command on your system to restart SSHD. This command typically involves invoking a service management tool or using the systemctl command for systemd-based systems.

Restart SSH Service on CentOS, RHEL, Fedora, Redhat, Alma, or Rocky Linux

Restarting SSH on CentOS, RHEL, Fedora, Redhat, Alma, or Rocky Linux is a straightforward process. You have a few options to accomplish this:

If you are using an older CentOS system or RHEL version, you can restart the SSH server using the init system. To do this, use the following command:

$ /etc/init.d/sshd restart

Alternatively, you can use the service command:

$ service sshd restart

For RHEL, CentOS, Fedora, Alma, or Rocky Linux systems running systemd (such as RHEL or CentOS versions 7, 8, 9), do the following:

Utilize the systemctl command, which is the preferred method for systemd-based systems:

$ sudo systemctl restart sshd

How To Restart SSH in Debian/ Ubuntu (Ubuntu Restart SSH) 

Restarting SSH in Debian or Ubuntu Linux is quite easy and simple. You can restart the SSH server in Linux using the different options that we have explained below:

Restart SSH Service Using Init Method

You can restart the SSH server using the init script method. Restart an SSH server by using the following command:

$ /etc/init.d/ssh restart

OR

$ service ssh restart

If you're not logged in as the root user, you can use the sudo to execute commands with root privileges:

$ sudo service ssh restart

Restart SSH Service Using systemd:

Utilize the systemctl command, which is the preferred method for systemd-based systems:

$ sudo systemctl restart ssh

If you are using a Linux VPS server, by executing any of these commands, you can effectively restart the SSH service, ensuring that any configuration changes take effect and allowing for secure remote connections to your system.

Command Line SSH Restart for Apple macOS 

To restart SSH on Apple macOS via the command line, open the Terminal application. Now, execute the following commands:

$ sudo launchctl unload /System/Library/LaunchDaemons/ssh.plist

$ sudo launchctl load -w /System/Library/LaunchDaemons/ssh.plist

Alternatively, you can use the below commands:

$ sudo launchctl stop com.openssh.sshd

$ sudo launchctl start com.openssh.sshd

SSH Restart on Windows

To restart the OpenSSH server on Windows, do the following:

1. Open PowerShell as an administrator.
2. Stop the OpenSSH server by running:

> Stop-Service sshd

1. Verify that the service has stopped by running:

> Get-Service sshd

1. Start the OpenSSH server again with the following:

> Start-Service sshd

1. Confirm that the service is running by re-running:

.> Get-Service sshd

Once restarted, you can connect to the OpenSSH server using an SSH client.

Basic SSHD Commands

Here, we listed some of the most commonly used SSHD commands that every system administrator or Linux user should know:

sshd: Controls the SSH server process, allowing you to start, stop, or restart the SSH service.

ssh-keygen: Generates pairs of public and private keys used for secure authentication and encryption.

ssh-copy-id: Simplifies setting up passwordless SSH login by copying your public key to a remote server's authorized_keys file.

ssh-agent: Manages private keys for SSH authentication, allowing you to enter your passphrase once per session.

ssh-add: Adds private keys to the ssh-agent, enabling it to use them for authentication.

SCP: Securely transfers files between local and remote hosts over SSH, ensuring encryption and authentication.

SFTP: Provides a secure alternative to FTP for file transfers, allowing encrypted file transfers over SSH.

These commands are essential for managing SSH connections, keys, and secure file transfers on a network.

Conclusion

In this tutorial, we demonstrated different methods to restart the SSH service on Linux or Unix-like systems. For further details, refer to the official OpenSSH documentation available on its official website. Additionally, if you want to learn more about the SSH client and SSH server, you can use the manual (man) command ‘man ssh’ in your terminal.