ssh — remote server connection

💬 "ssh command"

ssh opens an encrypted shell session to a remote server. It is the fundamental access path for server operations.

In practice, you use key authentication instead of passwords, together with options such as -p/-i/-L.

• Concept: An encrypted protocol that connects to a remote host and executes commands.
• Left: The connection target in user@host format.
• Options: Specify -p port, -i key file, -L tunnel, etc.
• Exit: Close the session with exit or Ctrl+D.

Commonly used options

3 essential command combinations

• ssh -p 22022 deploy@10.0.0.9 — Connect to the deployment account on a non-standard port
• ssh -i ~/.ssh/id_ed25519_gamehub root@10.0.0.9 — Connect as admin using the specified key
• ssh -L 5433:127.0.0.1:5432 deploy@10.0.0.9 — Tunnel a remote DB to a local port

💬 "Show me an example of using this to improve deployment stability"

Here are common situations on real production servers, organized in order.

Step 1 · Check reachability

First, check whether the port is open.

nc -vz 10.0.0.9 22 || nc -vz 10.0.0.9 22022

Step 2 · Connect

Connect by specifying the key and port.

ssh -i ~/.ssh/deploy_ed25519 -p 22022 deploy@10.0.0.9

Step 3 · Diagnose if there is a problem

If the connection doesn't work, use -v to see which step is failing.

ssh -v -p 22022 deploy@10.0.0.9

This is how it is used in practice

1. Emergency access to a production server

Situation — You receive an incident alert and need to get into a production server.

ssh -i ~/.ssh/prod_ed25519 ops@10.0.0.9

Result — You're connected immediately without a password using key authentication.

Point — Set up key authentication in advance so you don't have to look for a password in an emergency.

2. Remote DB tunnel

Situation — You cannot connect directly to the DB from your local machine because of a firewall.

ssh -N -L 5433:127.0.0.1:5432 ops@10.0.0.9

Result — Local port 5433 is connected to remote port 5432, so you can access it with local tools.

Point — -N opens only the tunnel without a shell. Close the session after you're done to clean up the tunnel.

Things to watch out for

• Direct root access is not recommended. Use a deployment account + sudo.
• Key file permissions must be 600. If they are too open, ssh will refuse.
• Tunnels (-L) are valid only while the connection is maintained. If the connection drops, you must reopen the tunnel.
• A host key change warning can indicate a man-in-the-middle attack, so do not blindly delete known_hosts.

Actual execution screen

This is the result of accessing the production server with key authentication and checking its status.

!ssh command execution result: remote access and status check

Production server in operation

Source (HTML): https://games.aidebatehub.com/programs/linux/remote/ssh.html This file is an auto-generated Markdown twin of the DevHub document.