PetexSpace

SSH Cheatsheet

This quick reference cheat sheet provides various for using SSH.

Getting Started

Public IP

Check this machine's public IP

$ curl myip.dog

Check a remote server's public IP (requires curl on the server)

$ ssh user@server 'curl myip.dog'

More IP tools: myip.dog

SCP

Copies from remote to local

$ scp user@server:/dir/file.ext dest/

Copies between two servers

$ scp user@server:/file user@server:/dir

Copies from local to remote

$ scp dest/file.ext user@server:/dir

Copies a whole folder

$ scp -r user@server:/dir dest/

Copies all files from a folder

$ scp user@server:/dir/* dest/

Copies from a server folder to the current folder

$ scp user@server:/dir/* .

Config location

File PathDescription
/etc/ssh/ssh_config
System-wide config
~/.ssh/config
User-specific config
~/.ssh/id_{type}
Private key
~/.ssh/id_{type}.pub
Public key
~/.ssh/known_hosts
Known Servers
~/.ssh/authorized_keys
Authorized login key

SCP Options

OptionsDescription
scp -r
Recursively copy entire directories
scp -C
Compresses data
scp -v
Prints verbose info
scp -P 8080
Uses a specific Port
scp -B
Batch mode (Prevents password)
scp -p
Preserves times and modes

Config sample

Host server1
    HostName 192.168.1.5
    User root
    Port 22
    IdentityFile ~/.ssh/server1.key

Launch by alias

$ ssh server1

See: Full Config Options

ProxyJump

$ ssh -J proxy_host1 remote_host2
$ ssh -J user@proxy_host1 user@remote_host2

Multiple jumps

$ ssh -J user@proxy_host1:port1,user@proxy_host2:port2 user@remote_host3

ssh-copy-id

$ ssh-copy-id user@server

Copy to alias server

$ ssh-copy-id server1

Copy specific key

$ ssh-copy-id -i ~/.ssh/id_rsa.pub user@server

SSH keygen

ssh-keygen

$ ssh-keygen -t rsa -b 4096 -C "[email protected]"
-t
Type of key
-b
The number of bits in the key
-C
Provides a new comment

Generate an RSA 4096 bit key with email as a comment, or use SSH Key Generator online

Generate

Generate a key interactively

$ ssh-keygen

Specify filename

$ ssh-keygen -f ~/.ssh/filename

Generate public key from private key

$ ssh-keygen -y -f private.key > public.pub

Change comment

$ ssh-keygen -c -f ~/.ssh/id_rsa

Change private key passphrase

$ ssh-keygen -p -f ~/.ssh/id_rsa

Key type

  • rsa

  • ed25519

  • dsa

  • ecdsa

known_hosts

Search from known_hosts

$ ssh-keygen -F <ip/hostname>

Remove from known_hosts

$ ssh-keygen -R <ip/hostname>

Key format

  • PEM

  • PKCS8

SSH Tunneling

SSH Tunnel Options

OptionDescription
-L
Local port forwarding
-R
Remote port forwarding
-D
Dynamic port forwarding
-f
Run in background
-N
Do not execute a remote command
-g
Allow remote hosts to connect to local forwarded ports

more details on flag above with man ssh

Local Port Forwarding

# Forward a local port to a remote server
ssh -L local_port:remote_host:remote_port user@ssh_server

# Example: Forward local port 8080 to remote port 80 on example.com
ssh -L 8080:example.com:80 user@ssh_server

Dynamic Port Forwarding

# Create a SOCKS proxy on a local port
ssh -D local_port user@ssh_server

# Create a SOCKS proxy on local port 1080 in the background
ssh -f -N -D 1080 user@ssh_server

Background Tunnel

# Create a local port forwarding tunnel in the background
ssh -f -N -L local_port:remote_host:remote_port user@ssh_server

Multiple Tunnels

# Create multiple tunnels in a single SSH command
ssh -L 8080:example.com:80 -L 3306:db.example.com:3306 user@ssh_server

Combining Options

# In background, no command, allow remote host, local port forward, identity_file
ssh -f -N -g -L 8080:example.com:80 -i ~/.ssh/custom_key user@ssh_server

Also see

Adapted from Fechin/referenceGPL-3.0 licenseMarkdown sourceChanges and attribution