SSH - Secure Shell #

https://selectel.ru/blog/ssh-ubuntu-setup/

Enabling SSH #

sudo apt update && sudo apt install openssh-server

sudo systemctl status ssh

sudo ufw allow ssh

Disabling SSH #

sudo systemctl disable --now ssh

Re-enable SSH #

sudo systemctl enable --now ssh

Disable password authentication in SSH #

sudo nano /etc/ssh/sshd_config

PasswordAuthentication no

sudo systemctl restart ssh

Create an RSA key pair #

ssh-keygen -t rsa

Correct file permissions for ssh keys and config #

ssh-keygen -t rsa -b 4096 -N '' -C "email@gmail.com" -f ~/.ssh/id_rsa
ssh-keygen -t rsa -b 4096 -N '' -C "email@gmail.com" -f ~/.ssh/github_rsa
ssh-keygen -t rsa -b 4096 -N '' -C "email@gmail.com" -f ~/.ssh/mozilla_rsa

chmod 700 ~/.ssh
chmod 644 ~/.ssh/authorized_keys
chmod 644 ~/.ssh/known_hosts
chmod 644 ~/.ssh/config
chmod 600 ~/.ssh/id_rsa
chmod 644 ~/.ssh/id_rsa.pub

chmod 600 ~/.ssh/github_rsa
chmod 644 ~/.ssh/github_rsa.pub

chmod 600 ~/.ssh/mozilla_rsa
chmod 644 ~/.ssh/mozilla_rsa.pub

ssh-agent #

eval "$(ssh-agent -s)"
ssh-add ~/.ssh/id_rsa
ssh-add ~/.ssh/github_rsa
ssh-add ~/.ssh/mozilla_rsa

Convert OpenSSH keys to Putty (.ppk) #

sudo apt install putty-tools

puttygen -t rsa -C ~/.ssh/id_rsa -o ~/.ssh/id_rsa.ppk

cd ~/.ssh/

puttygen id_rsa -o id_rsa.ppk

Custom cert #

ssh demo@ip-adress.my -i ~/.ssh/id_demo

.ssh/config #

Host demo
    HostName ip-adress.my
    User demo
    Port 7654
    IdentityFile ~/.ssh/id_demo
    LogLevel INFO
    Compression yes

Copy the public key file to your account on the remote system #

ssh-copy-id -i ~/.ssh/id_rsa.pub <server-user>@<server-public-ip-address>

with non-standard SSH Port #

ssh -o StrictHostKeyChecking=no deploy@${HOST} -p ${PORT} 'rm -rf site_${BUILD_NUMBER} && mkdir site_${BUILD_NUMBER}'

SSH tunnel to forward port #

ssh <host> -L<local_port>:<target_host>:<target_port>

# Example:
ssh <host> -L5306:localhost:3306
mysql -u<mysql_user> -p<mysql_pass> --protocol=tcp --port=5306 -hlocalhost <mysql_database>