SSH operator

Answer quick OpenSSH questions with a compact reference for connection flags, key generation and inspection, client configuration keywords, port forwarding forms, agent commands, scp and rsync syntax, and host key handling. Use when someone asks which SSH flag or config keyword to use, how a forwarding form is written, or wants a fast lookup rather than a guided workflow.

Add and repair entries in the SSH client configuration, covering host aliases, hostnames, users, ports, identity files, jump hosts, keep-alive settings, connection multiplexing, wildcard and pattern matching, Include files, and first-match-wins precedence. Use when a host alias must be created or fixed, when the wrong key or user is being used, when a jump host is needed, or when config changes appear to have no effect.

Inspect the SSH client version, key inventory, agent contents, effective per-host configuration, known-hosts entries, and reachability without changing anything or connecting where it is not needed. Use before an SSH operation, when a connection behaves unexpectedly, when it is unclear which key or user a host will use, or when the user asks whether SSH is set up.

Copy and synchronize files over SSH with scp, rsync, and sftp, covering direction, trailing-slash semantics, dry runs, deletion policy, permissions and ownership, excludes, resumable transfers, bandwidth limits, and verification by checksum or size. Use when files must move between a local machine and a remote host, when a directory must be synchronized, or when a previous transfer produced the wrong layout or deleted something.

Connect SSH to the systems around it, covering Git hosting authentication and signing, deploy keys, pipeline access through ephemeral keys, bastion and jump host chains, restricted authorized_keys entries for automation, remote Docker contexts, rsync-based deploys, and editor remote development. Use when a pipeline or another service needs SSH access to a host, when a repository must authenticate over SSH, or when access must be routed through a bastion.

Create, inspect, authorize, rotate, and revoke SSH key pairs, covering key types, passphrases, fingerprints, agent loading, authorized_keys entries with command and source restrictions, and separate keys per identity or per machine. Use when a key must be generated or replaced, when a key needs authorizing on a host, when a key is being retired, or when it is unclear which key a host trusts.

Open interactive SSH sessions and run remote commands non-interactively, covering batch mode and timeouts, quoting and here-documents, exit status and output capture, jump hosts, connection multiplexing, long-running work under tmux or screen, and safe handling of commands that change a remote host. Use when a command must run on a remote machine, when a session must be opened or kept alive, or when remote output has to be captured reliably.

Install or verify an OpenSSH client, create a first key pair, load it into the agent so a passphrase is typed once, set the correct file permissions, add a host entry, and authorize the public key on a server. Use when SSH is missing or unconfigured on a new machine, when a first key must be created and installed, or when the user asks how to get SSH working.

Diagnose SSH failures from reproducible evidence, covering unreachable ports, refused connections, publickey denials, wrong user or key selection, file permission problems, agent and passphrase failures, changed host keys, too many authentication failures, forwarding failures, and dropped or hanging sessions. Use when an SSH command fails, when a key that should work does not, when a host key warning appears, or when a session stalls.

Forward ports through SSH, covering local forwarding to reach a private service, remote forwarding to expose a local one, dynamic SOCKS proxies, jump hosts, bind addresses, background tunnels, and how to verify and tear one down. Use when a database or internal service must be reached through a bastion, when a local port must be reachable from a remote host, or when a tunnel is open but nothing connects through it.