Ssh Essentials

**Judgment:** This is a high-quality, practical SSH cheat sheet that covers nearly everything a typical developer or sysadmin needs for day-to-day SSH use, from basic connections through advanced tunneling, config, and file transfer. **Strengths** - Very comprehensive coverage: basic SSH, keys and ssh-agent, port forwarding (local/remote/dynamic), background tunnels, `~` escape sequences, config file usage, scp/sftp/rsync, hardening, and troubleshooting. - Commands are accurate, well-annotated, and largely aligned with modern OpenSSH practices (ed25519 keys, ProxyJump, multiplexing, etc.). - Good emphasis on security best practices (key-based auth, disabling passwords/root login, host key checking, permissions, fail2ban hint). - Strong usability: logically structured sections, clear comments, and examples that can be quickly adapted. **Key Risks / Caveats** - Some examples reduce security if copied blindly: - `ssh -o StrictHostKeyChecking=no` appears in multiple places; while one instance is marked “not recommended”, the earlier example isn’t, which may normalize insecure host key behavior. - Passphrase-less keys for automation are shown without explicit mention of mitigation steps (e.g., restricted accounts, limited privileges, key restrictions). - A few hardening recommendations (e.g. changing port, `Protocol 2`) are somewhat dated or of limited benefit on their own; they are not harmful but should be understood as part of a broader security posture. **Recommended Scenarios** - Teams standardizing on SSH for Linux/Unix server access and needing a single-page operational reference. - Individuals who already know the basics but want a compact guide to tunneling, ProxyJump, multiplexing, and rsync-over-SSH. - Use in internal docs or runbooks as an SSH appendix, with local security policies added to contextualize when to use riskier options (e.g., host key checking overrides, passwordless keys).