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SSH
SSH allows accessing a remote computer via a "secure shell". This provides a command line interface to a remote system that is accessible via your network.
ssh username@machine_address
It's usually best to configure public key authentication (and even disable password authentication).
Key pair is created (typically by the user). Typically:
ssh-keygen
Private key stays with the user (and only there), while the public key is sent to the server. Typically with the ssh-copy-id utility.
Server stores the public key (and "marks" it as authorized).
Server will now allow access to anyone who can prove they have the corresponding private key.
via: https://www.ssh.com/ssh/public-key-authentication
Use ssh-copy-id to transfer the public key to the machine you want to be able to log in to:
ssh-copy-id user@hostname.example.com
Or, if you're adding the id to a remote service like Github, show the public key:
cat .ssh/id_rsa.pub
SSH Server (SSHD)
If the machine doesn't have an ssh server running, you can install one:
sudo apt-get update
sudo apt-get -y install openssh-server
To find out ip
ip address
On older systems it was:
ifconfig
Known Hosts
ssh-keygen -R hostname
Migrating keys
If you migrate keys from one machine to another, be sure to update the ~/.ssh directory to have the correct permissions:
mkdir ~/.ssh
chmod 700 ~/.ssh
chmod 600 ~/.ssh/*mkdir ~/.ssh
chmod 700 ~/.ssh
chmod 600 ~/.ssh/*SSH Agent Forwarding
It's possible to use your local keys on machines that you connect to with
ssh -A
Make sure you're running sshagent
ps -aux | grep sshagent
https://developer.github.com/v3/guides/using-ssh-agent-forwarding/
SSH Port Forwarding
aka simple VPN.
Encrypts only the ports that you request to forward.
local port : remote address : remote port (??? TODO: confirm)
ssh account@address -L 5900:192.168.2.81:5900
For example, VNC often uses 5900
SSH Key Conversion
If a user sends a public key in an SSH2 text format, convert it to the form expected in authorized_keys:
ssh-keygen -i -f publickeyssh-keygen -i -f publickeyhttps://serverfault.com/questions/380712/ssh-public-key-format