Add 'zfs send --saved' flag

This commit adds the --saved (-S) to the 'zfs send' command.
This flag allows a user to send a partially received dataset,
which can be useful when migrating a backup server to new
hardware. This flag is compatible with resumable receives, so
even if the saved send is interrupted, it can be resumed.
The flag does not require any user / kernel ABI changes or any
new feature flags in the send stream format.

Reviewed-by: Paul Dagnelie <[email protected]>
Reviewed-by: Alek Pinchuk <[email protected]>
Reviewed-by: Paul Zuchowski <[email protected]>
Reviewed-by: Christian Schwarz <[email protected]>
Reviewed-by: Matt Ahrens <[email protected]>
Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: Tom Caputi <[email protected]>
Closes #9007 

1 files changed, 21 insertions, 0 deletions

diff --git a/man/man8/zfs-send.8 b/man/man8/zfs-send.8
index 0171166eb..2561cb61c 100644
--- a/man/man8/zfs-send.8
+++ b/man/man8/zfs-send.8
@@ -60,6 +60,10 @@
 .Fl t
 .Ar receive_resume_token
 .Nm
+.Cm send
+.Op Fl Pnv
+.Fl S Ar filesystem
+.Nm
 .Cm redact
 .Ar snapshot redaction_bookmark
 .Ar redaction_snapshot Ns ...
@@ -503,6 +507,23 @@ See the documentation for
 for more details.
 .It Xo
 .Nm
+.Cm send
+.Op Fl Pnv
+.Op Fl i Ar snapshot Ns | Ns Ar bookmark
+.Fl S
+.Ar filesystem
+.Xc
+Generate a send stream from a dataset that has been partially received.
+.Bl -tag -width "-L"
+.It Fl S, -saved
+This flag requires that the specified filesystem previously received a resumable
+send that did not finish and was interrupted. In such scenarios this flag
+enables the user to send this partially received state. Using this flag will
+always use the last fully received snapshot as the incremental source if it
+exists.
+.El
+.It Xo
+.Nm
 .Cm redact
 .Ar snapshot redaction_bookmark
 .Ar redaction_snapshot Ns ...