btrfs-progs: docs: update btrfs-send

Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/Documentation/btrfs-send.asciidoc b/Documentation/btrfs-send.asciidoc
index e05342f..1d54788 100644 (file)
--- a/Documentation/btrfs-send.asciidoc
+++ b/Documentation/btrfs-send.asciidoc
@@ -3,7 +3,7 @@ btrfs-send(8)
 
 NAME
 ----
 
 NAME
 ----

-btrfs-send - send data of subvolume(s) to stdout/file.
+btrfs-send - generate a stream of changes between two subvolumes

 
 SYNOPSIS
 --------
 
 SYNOPSIS
 --------


@@ -11,38 +11,49 @@ SYNOPSIS
 
 DESCRIPTION
 -----------
 
 DESCRIPTION
 -----------

-Sends the subvolume(s) specified by <subvol> to stdout.
-<subvol> should be read-only here.

 
 

-By default, this will send the whole subvolume. To do an incremental
-send, use '-p <parent>'.
+This command will generate a stream of instructions that describe changes
+between two subvolumes. The stream can be consumed by the *btrfs receive*
+command to replicate the sent subvolume on a different filesystem.
+The command operates in two modes: full and incremental.

 
 

-If you want to allow btrfs to clone from any additional local snapshots,
-use '-c <clone-src>' (multiple times where applicable). 
+All subvolumes involved in one send command must be read-only (ie. the
+read-only snapshots and this status cannot be changed if there's a running send
+operation that uses the subvolume).

 
 

-You must not specify clone sources unless you guarantee that these snapshots
-are exactly in the same state on both sides, the sender and the receiver.
+In the full mode, the entire subvolume data and metadata will end up in the
+stream.
+
+In the incremental mode (options '-p' and '-c'), there can be one or more
+parent subvolumes that will establish the base for determining the changes.
+The final stream will be smaller compared to the full mode.

 
 It is allowed to omit the '-p <parent>' option when '-c <clone-src>' options
 are given, in which case *btrfs send* will determine a suitable parent among the
 clone sources itself.
 
 
 It is allowed to omit the '-p <parent>' option when '-c <clone-src>' options
 are given, in which case *btrfs send* will determine a suitable parent among the
 clone sources itself.
 

+You must not specify clone sources unless you guarantee that these snapshots
+are exactly in the same state on both sides, the sender and the receiver.
+

 `Options`
 
 -v::
 `Options`
 
 -v::

-Enable verbose debug output. Each occurrence of this option increases the
-verbose level more.
+enable verbose output, print generated commands in a readable form, (each
+occurrence of this option increases the verbosity level)

 -e::
 -e::

-If sending multiple subvols at once, use the new format and omit the <end cmd> between the subvols.
+if sending multiple subvolumes at once, use the new format and omit the
+'end cmd' marker in the stream separating the subvolumes

 -p <parent>::
 -p <parent>::

-Send an incremental stream from <parent> to <subvol>.
+send an incremental stream from 'parent' to 'subvol'

 -c <clone-src>::
 -c <clone-src>::

-Use this snapshot as a clone source for an incremental send (multiple allowed).
+use this snapshot as a clone source for an incremental send (multiple allowed)

 -f <outfile>::
 -f <outfile>::

-Output is normally written to stdout. To write to a file, use this option.
-An alternative would be to use pipes.
+output is normally written to standard outout so it can be eg. piped to
+receive, use this option to write it to a file

 --no-data::
 --no-data::

-Send in NO_FILE_DATA mode. The output stream does not contain any file
+send in 'NO_FILE_DATA' mode
++
+The output stream does not contain any file

 data and thus cannot be used to transfer changes. This mode is faster and
 useful to show the differences in metadata.
 
 data and thus cannot be used to transfer changes. This mode is faster and
 useful to show the differences in metadata.