1/8/2024 0 Comments Ubuntu openssh serverOnce you’re satisfied with your configuration file, you can reload sshd to apply the new settings: In the event of a syntax error, there will be an output describing the issue. If your configuration file has a valid syntax, there will be no output. Now validate the syntax of your new configuration by running sshd in test mode: Note that this option most likely won’t already be present in the configuration file, so you may need to add it manually. You can now open the configuration file using your favorite text editor to begin implementing the initial hardening measures: ![]() This will run OpenSSH server in extended test mode, which will validate the full configuration file and print out the effective configuration values. This will save a backup copy of the file to /etc/ssh/sshd_config.bak.īefore editing your configuration file, you can review the options that are currently set. sudo cp /etc/ssh/sshd_config /etc/ssh/sshd_config.bak.Take a backup of the file using the following command: Before continuing with this tutorial, it is recommended to take a backup of your existing configuration file, so that you can restore it in the unlikely event that something goes wrong. Many of the hardening configurations for OpenSSH you implement using the standard OpenSSH server configuration file, which is located at /etc/ssh/sshd_config. However, the configuration you’ll use in this step is a general secure configuration that will suit the majority of servers. The exact hardening configuration that is most suitable for your own server depends heavily on your own threat model and risk threshold. In this first step, you will implement some initial hardening configurations to improve the overall security of your SSH server. Once you have this ready, log in to your server as your non-root user to begin. An Ubuntu 18.04 server set up by following the Initial Server Setup with Ubuntu 18.04, including a sudo non-root user.To complete this tutorial, you will need: ![]() In this tutorial, you will harden your OpenSSH server by using different configuration options to ensure that remote access to your server is as secure as possible. Properly securing your OpenSSH server is very important, as it acts as the front door or entry into your server. You can learn more about the SSH client-server model in SSH Essentials: Working with SSH Servers, Clients, and Keys. You can connect to an OpenSSH server using the OpenSSH client-the ssh command. OpenSSH server is the server side of SSH, also known as SSH daemon or sshd. Linux servers are often administered remotely using SSH by connecting to an OpenSSH server, which is the default SSH server software used within Ubuntu, Debian, CentOS, FreeBSD, and most other Linux/BSD-based systems. The author selected the Electronic Frontier Foundation Inc to receive a donation as part of the Write for DOnations program.
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