Add merlin_rmount documentation

pages/merlin6/02-How-To-Use-Merlin/transfer-data.md

@@ -2,13 +2,34 @@
 title: Transferring Data
 #tags:
 keywords: transferring data, data transfer, rsync, winscp, copy data, copying, sftp, import, export, hop, vpn
-last_updated: 07 September 2022
+last_updated: 24 August 2023
 #summary: ""
 sidebar: merlin6_sidebar
 permalink: /merlin6/transfer-data.html
 ---
 
-## Transferring Data from the PSI Network to/from Merlin6
+## Overview
+
+Most methods allow data to be either transmitted or received, so it may make sense to
+initiate the transfer from either merlin or the other system, depending on the network
+visibility.
+
+- Merlin login nodes are visible from the PSI network, so direct data transfer
+  (rsync/WinSCP) is generally preferable. This can be initiated from either endpoint.
+- Merlin login nodes can access the internet using a limited set of protocols
+  - SSH-based protocols using port 22 (rsync-over-ssh, sftp, WinSCP, etc)
+  - HTTP-based protocols using ports 80 or 445 (https, WebDav, etc)
+  - Protocols using other ports require admin configuration and may only work with
+    specific hosts (ftp, rsync daemons, etc)
+- Systems on the internet can access the Remote Access Merlin servers
+  (ra-merlin*.psi.ch) using ssh-based protocols
+
+
+## Direct transfer via Merlin6 login nodes
+
+The following methods transfer data directly via the [login
+nodes](/merlin6/interactive.html#login-nodes-hardware-description). They are suitable
+for use from within the PSI network.
 
 ### Rsync
 
@@ -37,9 +58,10 @@ from the Software Kiosk on PSI machines. Add `merlin-l-01.psi.ch` as a host and
 connect with your PSI credentials. You can then drag-and-drop files between your
 local computer and merlin.
 
-## Transferring Data to/from outside PSI
 
-Two servers are enabled for exporting data from Merlin outside PSI, as well as for importing data. 
+## Remote Access Servers
+
+Two servers are enabled for data transfers originating from outside PSI.
 This is a central service managed by a different team, which is managing the different Remote Access 
 services at PSI for the different facilities (including the one for Merlin). However, any problems 
 or questions related to it can be directly [reported](/merlin6/contact.html) to the Merlin adminstrators, 
@@ -132,3 +154,18 @@ Merlin6 is fully accessible from within the PSI network. To connect from outside
 - [No Machine](nomachine.md)
    * Remote Interactive Access through [**'rem-acc.psi.ch'**](https://www.psi.ch/en/photon-science-data-services/remote-interactive-access)
    * Please avoid transferring big amount of data through **NoMachine**
+
+## Connecting from Merlin6 to outside file shares
+
+### `merlin_rmount` command
+
+Merlin provides a command for mounting remote file systems, called `merlin_rmount`. This
+provides a helpful wrapper over the Gnome storage utilities, and provides support for a wide range of remote file formats, including
+- SMB/CIFS (Windows shared folders)
+- WebDav
+- AFP
+- FTP, SFTP
+- [others](https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/8/html/using_the_desktop_environment_in_rhel_8/managing-storage-volumes-in-gnome_using-the-desktop-environment-in-rhel-8#gvfs-back-ends_managing-storage-volumes-in-gnome)
+
+
+[More instruction on using `merlin_rmount`](/merlin6/merlin-rmount.html)