master: ssh: connect to host master port 22: No route to host

This error message indicates that your SSH client is unable to connect to the specified host (in this case, "master") on port 22.

There are several possible reasons for this error, including:

1. The host is not reachable: Check if the host is online and if there is any network issue preventing your client from reaching the host. You can try pinging the host to see if it is reachable.

2. The SSH service is not running: Make sure that the SSH service is running on the remote host. You can check if the SSH service is running using the command "systemctl status ssh" on the remote host.

3. The firewall is blocking the connection: Check if there is any firewall or security group configuration that is blocking the SSH connection. You can try disabling the firewall temporarily to see if it resolves the issue.

4. Incorrect SSH configuration: Check if the SSH configuration on the client and server is correct. Make sure that the hostname, port number, and SSH key are all correct.

5. DNS resolution issue: Check if the hostname is resolving to the correct IP address. You can try using the IP address instead of the hostname to connect to the host.

Once you have identified the root cause of the issue, you can take appropriate action to resolve it.