From fb001b6c01e910030c3b184321185970ebba7ef5 Mon Sep 17 00:00:00 2001
From: edwardxml <56691903+edwardxml@users.noreply.github.com>
Date: Mon, 23 Nov 2020 16:34:27 +0000
Subject: [PATCH] docs: improve "rclone about" docs and relate to union mfs
 limitation in ftp remote

See: https://forum.rclone.org/t/rclone-union-mfs-most-free-space-not-working-for-ftp/20346
---
 docs/content/ftp.md      |  5 +++++
 docs/content/overview.md | 17 +++++++++--------
 2 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/docs/content/ftp.md b/docs/content/ftp.md
index 94827dba2..b80da56d5 100644
--- a/docs/content/ftp.md
+++ b/docs/content/ftp.md
@@ -236,6 +236,11 @@ through rclone are time of upload.
 Rclone's FTP backend does not support any checksums but can compare
 file sizes.
 
+`rclone about` is not supported by the FTP backend. Backends without
+this capability cannot determine free space for an rclone mount or
+use policy `mfs` (most free space) as a member of an rclone union
+remote. [More](https://rclone.org/overview/#optional-features)
+
 The implementation of : `--dump headers`,
 `--dump bodies`, `--dump auth` for debugging isn't the same as
 for rclone HTTP based backends - it has less fine grained control.
diff --git a/docs/content/overview.md b/docs/content/overview.md
index 19e9bd8bb..cc235c733 100644
--- a/docs/content/overview.md
+++ b/docs/content/overview.md
@@ -318,9 +318,8 @@ remote itself may assign the MIME type.
 
 ## Optional Features ##
 
-All the remotes support a basic set of features, but there are some
-optional features supported by some remotes used to make some
-operations more efficient.
+All rclone remotes support a base command set. Other features depend
+upon backend specific capabilities.
 
 | Name                         | Purge | Copy | Move | DirMove | CleanUp | ListR | StreamUpload | LinkSharing | About | EmptyDir |
 | ---------------------------- |:-----:|:----:|:----:|:-------:|:-------:|:-----:|:------------:|:------------:|:-----:| :------: |
@@ -424,13 +423,15 @@ on the particular cloud provider.
 
 ### About ###
 
-This is used to fetch quota information from the remote, like bytes
-used/free/quota and bytes used in the trash.
+Rclone `about` prints quota information for a remote. Typical output
+includes bytes used, free, quota and in trash.
 
-This is also used to return the space used, available for `rclone mount`.
+If a remote lacks about capability `rclone about remote:`returns
+an error.
 
-If the server can't do `About` then `rclone about` will return an
-error.
+Backends without about capability cannot determine free space for an
+rclone mount, or use policy `mfs` (most free space) as a member of an
+rclone union remote.
 
 ### EmptyDir ###