Explanations on possible values for transport.socket.ssl-cert-depth are missing

[johanneskastl]

glusterdocs/docs/Administrator-Guide/SSL.md

Line 166 in 78bfdf9

## Enabling TLS on the Management Path

The file /var/lib/glusterd/secure-access may or may not contain a line with the transport.socket.ssl-cert-depth option.

The Guide is missing something like the following:

Creating an empty file is enough to enable TLS encryption of the management traffic.

By specifying 'option transport.socket.ssl-cert-depth X' inside that file you can influence the verification of TLS certificates:
- a value of '0' means ...
- a value of '1' (which is the default) means that '/etc/ssl/glusterfs.ca' contains a list of TLS certificates that are to be allowed
- a value of '2' means that  '/etc/ssl/glusterfs.ca' contains a CA certificate, and all TLS certificates that are signed by this CA are to be allowed
- a value of '3' means that  '/etc/ssl/glusterfs.ca' contains a CA certificate, and all TLS certificates that are signed by this CA's intermediae CA are to be allowed 
...

I am fishy on the exact details, as there does not seem to be a comprehensive list of the values in the docs. When using an empty file, the value seems to default to 1 according to the output on one of our servers.

Edit:
It would make sense to point out that apparently (at least in our tests) an empty file is enough for a client, but the server needs the right setting, otherwise clients may not be allowed to mount...