SSH Command Cheat Sheet

This cheat sheet provides a quick reference for common SSH commands and options. These commands are essential for remote server management, file transfers, and configuring secure connections.

Basic SSH Commands

Connecting to a Remote Server

ssh user@hostname

Establishes an SSH connection to the remote server. Replace user with the username and hostname with the server’s domain or IP address.

Specifying a Non-Default Port

ssh -p 2222 user@hostname

Connects to a remote server using a non-default port (e.g., 2222 instead of the default port 22).

Running a Command Remotely

ssh user@hostname 'command'

Executes a command on the remote server without opening an interactive session.

Using SSH with a Specific Identity File (Private Key)

ssh -i /path/to/private_key user@hostname

Specifies an identity file (private key) for the SSH connection.

File Transfers with SSH

Copying Files to a Remote Server (scp)

scp localfile.txt user@hostname:/remote/directory/

Copies localfile.txt from the local machine to the specified remote directory.

Copying Files from a Remote Server (scp)

scp user@hostname:/remote/directory/remotefile.txt /local/directory/

Copies remotefile.txt from the remote server to the specified local directory.

Using rsync for Efficient File Synchronization

rsync -avz -e ssh localfile.txt user@hostname:/remote/directory/

Uses rsync to efficiently synchronize files between the local system and the remote server over SSH, transferring only the differences.

Port Forwarding and Tunneling

Local Port Forwarding

ssh -L local_port:remote_host:remote_port user@hostname

Forwards a local port to a remote host and port, making it possible to securely access services running on the remote machine. For example:

ssh -L 8080:localhost:80 user@hostname

Remote Port Forwarding

ssh -R remote_port:local_host:local_port user@hostname

Forwards a port from the remote server to the local machine. This is useful for exposing local services to the remote server.

Dynamic Port Forwarding (SOCKS Proxy)

ssh -D local_port user@hostname

Sets up a SOCKS proxy on the local machine, routing traffic through the SSH connection. This can be useful for browsing securely through a remote server.

Other Common Options

Verbose Mode

ssh -v user@hostname

Enables verbose output for debugging purposes. Additional verbosity can be added with -vv or -vvv.

Disabling Host Key Checking

ssh -o StrictHostKeyChecking=no user@hostname

Disables the host key verification step, often used in automated scripts. Be cautious, as this reduces security by not verifying the server’s identity.

Using an SSH Proxy (Jump Host)

ssh -J user@jump-host user@internal-host

Connects to a remote internal server by routing the connection through a jump host.

This cheat sheet provides a summary of essential SSH commands and options. These commands enable secure and efficient remote server management, file transfers, and tunneling over SSH.