ssh

Connect with specific key Specify an identity file explicitly ssh -i ~/.ssh/id_ed25519 user@host #ssh ProxyJump through bastion Single-hop jump through bastion host ssh -J bastion.example.com user@internal-host #ssh#network Multi-hop jump chain Chain multiple jump hosts in one command ssh -J user@bastion1,user@bastion2 user@target #ssh#network Local port forward Forward localhost:5432 to db.internal:5432 via bastion ssh -L 5432:db.internal:5432 user@bastion -N #ssh#network Remote port forward Expose local port 3000 as port 8080 on VPS ssh -R 8080:localhost:3000 user@vps -N #ssh#network Dynamic SOCKS proxy Create a local SOCKS5 proxy tunnelled through VPS ssh -D 1080 user@vps -N -f #ssh#network#security SSH multiplexing (ControlMaster) Reuse existing connection for subsequent SSH commands ssh -o ControlMaster=auto -o ControlPath=~/.ssh/mux-%r@%h:%p -o ControlPersist=10m user@host #ssh#performance Run remote command Execute a command over SSH without interactive shell ssh user@host 'sudo systemctl status nginx' #ssh Copy file via SCP Recursive copy on non-standard port scp -r -P 2222 ./dist/ user@host:/var/www/app/ #ssh Agent forwarding Forward local SSH agent to the remote host (use with caution) ssh -A user@bastion #ssh#security Add key to agent Start agent and load a key for the session eval $(ssh-agent) && ssh-add ~/.ssh/id_ed25519 #ssh SSH config file host entry Shorthand alias: 'ssh dev' triggers all options cat >> ~/.ssh/config <<'EOF' Host dev HostName 10.0.0.5 User ubuntu IdentityFile ~/.ssh/dev_key ProxyJump bastion EOF #ssh Escape sequences in session Terminate a frozen/hung SSH session: type tilde then dot ~. #ssh#debug Check SSH server host key Fetch and fingerprint server host keys without connecting ssh-keyscan -t ed25519,rsa host 2>/dev/null | ssh-keygen -lf - #ssh#security Restrict authorized key Force-command and restrict source IP in authorized_keys echo 'from="10.0.0.0/8",no-agent-forwarding,no-port-forwarding,command="/usr/bin/backup.sh" <pubkey>' >> ~/.ssh/authorized_keys #ssh#security