Openssh

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.

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.

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.

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.