How to test the sshd configuration for configuration errors?
Before reloading the SSH configuration, perform a configuration test first. This may avoid locking yourself out of a remote system or break any existing communications between the server and any clients. Testing can be done using the sshd command. For this purpose, it has the -t option available.
Command line usage
To use this option on the command line, run the following command:
sshd -t
