Improved Geo documentation to include SSH keys detailed instructions

doc/gitlab-geo/configuration.md

@@ -56,8 +56,13 @@ primary node (**Admin Area > Geo Nodes**) when adding a new one:
 sudo -u git -H ssh-keygen
 ```
 
-The public key for Omnibus installations will be at `/var/opt/gitlab/.ssh/id_rsa.pub`,
-whereas for installation from source it will be at `/home/git/.ssh/id_rsa.pub`.
+Remember to add your primary node to the `known_hosts` file of your `git` user.
+
+You can find ssh key files and `know_hosts` at `/var/opt/gitlab/.ssh/` in
+Omnibus installations or at `/home/git/.ssh/` when following the source
+installation guide.
+
+
 
 If for any reason you generate the key using a different name from the default
 `id_rsa`, or you want to generate an extra key only for the repository
@@ -170,6 +175,9 @@ to fix (all commands and path locations are for Omnibus installs):
       expect something like: `#<GeoNode id: 2, schema: "https", host: "gitlab.example.com", port: 443, relative_url_root: "", primary: false, ...>`
     - By running the command above, `primary` should be `true` when executed in
       the primary node, and `false` on any secondary
+- Did I defined the correct SSH Key for the node?
+    - You must create an SSH Key for `git` user
+    - This key is the one you have to inform at `Admin > Geo`
 - Can primary node communicate with secondary node by HTTP/HTTPS ports?
 - Can secondary nodes communicate with primary node by HTTP/HTTPS/SSH ports?
 - Can secondary nodes execute a succesfull git clone using git user's own