The SSH Commands Cheat Sheet You’ll Regret Missing Out On

May 17, 2023 / By Cassandra Lee

Whether you need a quick recap of SSH commands or you’re learning SSH from scratch, nothing beats a handy guide. It’s easy to get overwhelmed knowing what SSH or OpenSSH commands are important enough for your current task. SSH is necessary for network administrators and anyone who needs to log in to remote computers and servers.

The good news is: we’ve brought you a neat, no-nonsense SSH cheat sheet suitable for beginners and advanced users. It covers basic SSH commands, SSH configurations and options, remote server management, advanced SSH commands, and tunneling, including using a router and Wireshark to capture web traffic on a remote host.

Download our SSH commands cheat sheet here. When you’re ready, let’s dive in.

What Is SSH?

SSH (short for “Secure Shell” or “Secure Socket Shell”) is a network protocol for accessing network services securely over unsecured networks. It includes the suite of utilities implementing it, such as:

• ssh-keygen: for creating new authentication key pairs for SSH;
• SCP (Secure Copy Protocol): for copying files between hosts on a network;
• SFTP (Secure File Transfer Protocol): for sending and receiving files. It’s an SSH-secured version of FTP (File Transfer Protocol), and it has replaced FTP and FTPS (FTP Secure) as the preferred mechanism for file sharing over the Internet.

An SSH server, by default, listens for connections on the standard Transmission Control Protocol (TCP) port 22. Your applications may listen for SSH connections on other ports.

SSH lets you securely manage remote systems and applications, such as logging in to another computer over a network, executing commands, and moving files from one computer to another. An advanced SSH functionality is the creation of secure tunnels to run other application protocols remotely.

Basic SSH Commands

The following are fundamental SSH commands. Commit as many to memory as you can.

SSH Configurations and Options

Have you ever wondered how SSH remembers your login credentials for various machines? This section is a brief reference on how to do so.

Remote Server Management

The operating systems of SSH servers are mostly Unix/Linux, so once you’ve logged in to a server via SSH, the following commands are largely the same as their counterparts in Unix/Linux. Check out our Unix commands cheat sheet and Linux command line cheat sheet for other file management commands applicable to SSH.

Using PowerShell to access a lab account on a network computer via SSH on Windows 10

Advanced SSH Commands

This table lists some complex SSH utilities that can help with network administration tasks: SSH File System (SSHFS), data compression, and X11 forwarding.

To conduct X11 forwarding over SSH, do these three things:

1. Set up your client (~/.ssh/config) to forward X11 by setting these parameters:
   Host *
ForwardAgent yes
ForwardX11 yes
2. Set up your server (/etc/ssh/sshd_config) to allow X11 by setting these parameters:
   X11Forwarding yes
X11DisplayOffset 10
X11UseLocalhost no
3. Set up X11 authentication on your server by installing xauth.

Tunneling

These SSH command line options create secure tunnels.

SSH Tunneling Demonstration

Let’s show you two ways to pipe traffic from your router into Wireshark and monitor your network activity. The first demonstration involves installing programs onto a system used as a router; the second, without.

Using Django

As a demonstration, we’re piping traffic from a router into Wireshark, so that we can monitor live web traffic through an SSH tunnel. (The router below is a macOS computer hosting a Kali Linux virtual machine using the Wireshark instance installed on the latter.)

The setup is as follows:

1. On the router: Enable remote access via SSH. (NOTE: On the macOS system, go to System Preferences > Sharing > turn on Remote Login and note the login username and hostname. For your router setup, check your specific manufacturer's guide to enable remote access via SSH.)
2. On the router: Install Python Django and start up the Django template server on http://127.0.0.1:8000 using the Terminal command string django-admin startproject mysite; cd mysite; python manage.py runserver (or python3 manage.py runserver). Note the Django web app uses port 8000.
3. On Kali Linux: execute this command to listen on port 8080: ls | nc -l -p 8080
4. On Kali Linux: execute this command in a different Terminal tab/window. Below, 8000 is the router’s Django port, 8080 is the Kali Linux listening port on localhost, and the command involves remote port forwarding (-R): sudo ssh -R 8000:localhost:8080 user@router_ip
5. On Kali Linux: start Wireshark and select the loopback interface (lo) as the capture device. Wireshark should be sniffing packets on lo now.
6. On the router: visit http://127.0.0.1:8000 in a web browser. (Note localhost and 127.0.0.1 are equivalent.) The Django server wouldn’t load; it freezes instead because of the rerouted traffic.
7. On Kali Linux: You should expect the following results:

Piping traffic of Django web app http://127.0.0.1:8000 on the macOS router into the Wireshark instance on Kali Linux

Wireshark HTTP packet corresponding to the Django web app on the router

Using tcpdump

The following is an alternative method for capturing remote web traffic passing through a router.

In Kali Linux, you’ll log in to your router via SSH, capture packets with the command-line packet capturing tool tcpdump, and pipe the traffic into Wireshark.

Here is the required command with the option flags explained:

Example of piping router traffic to Wireshark via tcpdump

After executing the command above, Wireshark opens:

Wireshark triggered

Next, the SSH client will prompt you to input your router password. Pasting it suffices:

SSH login successful. Now, tcpdump packet capture begins:

Meanwhile, Wireshark receives the piped traffic from tcpdump:

That’s it.

Conclusion

We have covered SSH, SCP, SFTP, SSH configuration commands such as ssh-agent, ssh-add, and ssh-copy-id, and various SSH tunneling commands.

Here are some tips for using SSH more efficiently and securely:

• Disable X11 and TCP forwarding because attackers can use such weaknesses to access other systems on your network. Change the options on sshd_config to be AllowTcpForwarding no and X11Forwarding no.
• Change the default options on sshd_config, such as changing the default port from 22 to another number.
• Authenticate clients using SSH certificates created with ssh-keygen.
• Use a bastion host with the help of tunneling commands.
• Restrict SSH logins to specific IPs, such as adding user filtering with the AllowUsers option in sshd_config.

Thanks to its security measures and the ubiquity of networking tasks, SSH is indispensable for computer data communications. Hence every student and professional in IT and cyber security needs a working knowledge of SSH commands, and we hope this SSH cheat sheet is a good starter or refresher for you.

To learn more about SSH and secure network administration, check out the following courses from us: