Ssh
How to see the SSH log?
SSH logs authentication attempts, but where? Find your SSH log file with these tips, such as in /var/log/auth.log or in the systemd journal.
How to test the sshd configuration for configuration errors?
A healthy service should not have configuration issues. Perform a configuration test of the SSH daemon (sshd) by first running it using the '-t' option.
What is SSH?
SSH (secure shell) is a network protocol to provide secure remote access to systems, comes with strong authentication and encrypted data communication.
How to add a SSH key to the SSH agent
Learn how to load and use your SSH key together with a SSH agent. This frequently asked question will explain the usage of ssh-add and ssh-agent.
SSH ProxyJump option
Learn about the SSH client option ProxyJump, that allows using a bastion host or jump server to connect to other systems.
SSH ForwardAgent option
Secure SSH connections and learn about the ForwardAgent option, the available values, relevant security risks, and how to configure it.
What is SSH agent forwarding?
The agent forwarding feature in SSH allows using your local SSH agent to be reached through an existing SSH connection. Learn when and how to use it.
How to start the SSH agent?
The OpenSSH agent helps with authentication by making SSH keys available. Learn how to start the SSH agent when it is not running on your Linux system.
What is the purpose of the SSH agent?
The SSH agent is a helper utility to temporarily store private keys when using public key authentication. Learn more about how this helps during daily tasks.
How to disable the usage of the SSH agent
The SSH agent can be used to simplify authentication. As that is not always preferred behavior, we can disable the SSH agent when authenticating.
SSH IdentityAgent option
OpenSSH can be configured to use an alternative SSH agent, or even none. Learn about the IdentityAgent option, available values, and how to configure it.
/etc/ssh/ssh_config
The configuration file /etc/ssh/ssh_config contains settings related to the OpenSSH client. Learn more about this file its configuration.
SSH client configuration
Linux systems are usually managed remotely with SSH. Learn how to configure and optimize the SSH client and improve its security.
SSH configuration files
OpenSSH can be configured on the server and client. Learn about the locations where SSH client settings are configured and what precedence they take.
SSH StrictHostKeyChecking option
Secure your OpenSSH configuration and learn about the StrictHostKeyChecking option, available values, and how to configure it.
SSH PasswordAuthentication option
Secure SSH connections and learn about the PasswordAuthentication option, its available values, and how to configure it.
How to disable the SSH host key check?
OpenSSH performs a host authenticity check when connecting to a system. Learn how to disable the check with the SSH option StrictHostKeyChecking.
Change SSH server port number
Learn how to make changes to your SSH configuration to have it running on a different port. Change it from port 22 to something like 2222.
Configure a SSH welcome message or banner
Configure a welcome message or banner for users to see before or after logging in via SSH. Here are the instructions to change the relevant configuration files.
SSH escape sequences
OpenSSH has escape sequences available to initiate special commands during an active SSH session. Learn about the available escape sequences with this overview.
How to terminate a SSH connection that does not respond to CTRL+C
Learn about SSH escape sequences and how they can help with terminating a SSH connection that does not respond to CTRL+C.
How to remove the passphrase from a SSH key
While protecting SSH keys is typically advised, it is not always feasible in automated processes. Learn how to remove the password or passphrase from a SSH key.
How to see the available SSH keys in the OpenSSH authentication agent
The SSH agent can load stored SSH keys into memory for authentication purposes. Use the ss-add command to show the available SSH keys that are loaded.
SSH: Frequently Asked Questions
Frequently asked questions about SSH, such as SSH keys, configuration, and usage.
/etc/ssh/sshd_config
The configuration file /etc/ssh/sshd_config contains settings related to the OpenSSH server daemon. Learn more about this file its configuration.
SSH Configuration
The configuration settings and suggestions related to the SSH client and SSH server daemon.
SSH
OpenSSH is one of the most-used components on Linux systems. This sections collects articles, commands, and settings to configure the SSH server and client.
How to find the OpenSSH version
Searching for the installed version of OpenSSH? Here are some commands to discover what software you are running, including the related packages.
Restrict SSH access to only allow rsync
Want to restrict SSH access to only allow rsync file synchronization? This article explains the steps and how to set it up.
OpenSSH security and hardening
The SSH configuration influences the security of your Linux system. This guide helps you to secure your OpenSSH server and client configuration.
Using Ed25519 for OpenSSH keys (instead of DSA/RSA/ECDSA)
Many years the default for SSH keys was DSA or RSA. There is a new kid on the block, with the fancy name Ed25519. Let's have a look at this new key type.
The real purpose of login banners (on Linux)
We are used seeing login banners everywhere. What is the point of them, and why would they be useful? The answer is more surprising than you expected.
Mosh, the SSH Alternative Option for System Administration
Learn about Mosh, an alternative for SSH. Let's dive into the reasons why it makes sense to learn about Mosh and how to use it.
Granting temporary access to your servers (using signed SSH keys)
SSH has the capabilities to give a colleague or vendor temporary access to your systems. Learn how to install and configure the related SSH settings.
Distributing SSH keys: using ssh-copy-id, manually, or automated
Learn how to get your SSH keys easier to another system using different available methods such as manually or a tool like ssh-copy-id
In-depth Linux Guide to Achieve PCI DSS Compliance and Certification
This is the technical Linux guide to achieve compliance with the PCI DSS standard. Become compliant, with Linux tips for configuration and auditing.
Using SSH keys instead of passwords
Linux systems are usually managed remotely with SSH, often still using passwords. Time to switch over to SSH keys and here is how to do that.
SSH server configuration
Linux systems are usually managed remotely with SSH. Learn how to configure the SSH server daemon and improve its security.
Audit SSH configurations: HashKnownHosts option
Information about the HashKnownHosts option in the SSH configuration file. Explains how to audit and tune this option to secure an Unix based system.