find-ssh-host

name	find_ssh_host
description	Find an SSH host on the local network and update ~/.ssh/config with its current IP address

Find SSH Host

This skill uses the ssh-find script to scan the local network for an SSH host defined in ~/.ssh/config, identify it by hostname, and update the config file with the host's current IP address.

Prerequisites

• nmap must be installed (brew install nmap on macOS, sudo apt-get install nmap on Linux)
• The ~/opt/bin/ssh-find script must be available (installed via dotfiles)
• The target host alias must already exist in ~/.ssh/config
• The SSH key referenced in the config must be present locally

Steps

1. Prompt for the Host Alias

Ask the user which SSH host alias they want to find. The alias must match a Host entry in ~/.ssh/config.

If the user has already provided a host alias in their request, use that value directly without prompting.

2. Validate the Host Alias

Run the following command to confirm the alias exists in the SSH config:

ssh -G <HOST_ALIAS> 2>/dev/null | head -5

• If the command succeeds (exit code 0), the alias is valid. Extract and display the current hostname and user from the output for the user's reference.
• If the command fails, inform the user that the alias was not found in ~/.ssh/config and stop.

3. Run ssh-find

Execute the ssh-find script via the terminal. This script is interactive — it will scan the network and prompt for confirmation before updating the config.

~/opt/scripts/network/ssh-find <HOST_ALIAS>

Important: This command is interactive. It will:

1. Scan the local subnet for SSH-enabled hosts using nmap (may require sudo)
2. Test each discovered IP by connecting with the configured SSH key
3. For each successful connection, display the remote hostname and ask: Is this the correct host for '<HOST_ALIAS>'? (y/n):

You must monitor the terminal output and:

• When prompted with (y/n), ask the user whether the displayed hostname matches the host they are looking for.
• Send y or n based on the user's answer.

4. Report Results

After the script completes, report the outcome to the user:

• Success: The SSH config was updated. Show the new IP address and note that a backup was created at ~/.ssh/config.bak.
• No match found / No SSH hosts found: The script scanned all discovered hosts but none were confirmed.
  • If a MAC address for <HOST_ALIAS> exists in ~/.ssh/wol_map.json, the ssh-find script will automatically offer to send a Wake-on-LAN magic packet.
  • Follow the script's interactive prompts (confirm with the user if they want to wake the host).
  • If the script doesn't offer WOL but the user provides a MAC address, you can run wol <MAC_ADDRESS> manually.
  • Inform the user if a packet was sent and suggest waiting a minute before retrying.

5. Verify the Update (on success)

If the config was updated, verify by running:

ssh -G <HOST_ALIAS> 2>/dev/null | grep "^hostname "

Display the updated hostname value to confirm the change took effect.