SSH

SSH#

#

Connecting#

Connect to a server (default port 22)

$ ssh root@192.168.1.5

Connect on a specific port

$ ssh root@192.168.1.5 -p 6222

Connect via pem file (0400 permissions)

$ ssh -i /path/file.pem root@192.168.1.5

Executing#

Executes remote command

$ ssh root@192.168.1.5 'ls -l'

Invoke a local script

$ ssh root@192.168.1.5 bash < script.sh

Compresses and downloads from a server

$ ssh root@192.168.1.5 "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

Known Servers

~/.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 "your@mail.com"

-

-

-

-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

SSH Tunneling#

SSH Tunnel Options#

Option

Description

-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#

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