Linux SSH Commands

ssh user@host starts a remote shell. Per-host defaults live in ~/.ssh/config: IdentityFile, Port, ProxyJump for bastions, and StrictHostKeyChecking policies. Keys beat passwords—protect private keys with passphrases and ssh-agent. Copy files with scp or rsync -e ssh. Review server settings with sshd -T on the host.

Task	Command	Tip
Jump host	ssh -J bastion user@internal	ProxyJump in config for teams
Forward agent	ssh -A	Risky on untrusted servers
Debug	ssh -vvv	Shows KEX and auth steps

Linux security commands, bastion hosts, sudo, networking commands

It stores per-host aliases, ports, identities, and jump settings so you avoid long command lines.

A malicious admin on the remote host can use your forwarded agent to authenticate to other systems as you.

Publish new keys, update known_hosts with ssh-keygen -R, then verify fingerprints out-of-band.

Older ProxyCommand chains for bastion access—ProxyJump is simpler for multi-hop SSH.

Pass the command after the host: ssh user@host 'systemctl is-active nginx'.

They are short, fast, and avoid legacy RSA parameter choices—use modern OpenSSH key types.

Host key checks may warn if IP changes—verify the key fingerprint matches the same server identity.

scp is simple for small copies; rsync adds delta sync and resumes for large trees.

Task	Command	Tip
Jump host	ssh -J bastion user@internal	ProxyJump in config for teams
Forward agent	ssh -A	Risky on untrusted servers
Debug	ssh -vvv	Shows KEX and auth steps