SSH

Getting started

ssh is a network client and server program for Unix-like operating systems such as Linux, macOS, and Windows.

Connecting

Connect to a server (default port 22)

$ ssh [email protected]

Connect on a specific port

$ ssh [email protected] -p 6222

Connect via pem file (0400 permissions)

$ ssh -i /path/file.pem [email protected]

See: SSH Permissions

Executing

Executes remote command

$ ssh [email protected] 'ls -l'

Invoke a local script

$ ssh [email protected] bash < script.sh

Compresses and downloads from a server

$ ssh [email protected] "tar cvzf - ~/source" > output.tgz

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 Path Description
/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 Logged in host
~/.ssh/authorized_keys Authorized login key

SCP Options

Options Description
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

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

See also