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Make the --append* options have more warnings.

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Wayne Davison
2020-07-27 15:05:11 -07:00
parent e1e546d67e
commit 3f83bcb4af
1 changed files with 21 additions and 20 deletions
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rsync.1.md
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@@ -938,30 +938,31 @@ your home directory (remove the '=' for that).
0. `--append`
This causes rsync to update a file by appending data onto the end of the
file, which presumes that the data that already exists on the receiving
side is identical with the start of the file on the sending side. If a
file needs to be transferred and its size on the receiver is the same or
longer than the size on the sender, the file is skipped. This does not
interfere with the updating of a file's non-content attributes (e.g.
permissions, ownership, etc.) when the file does not need to be
transferred, nor does it affect the updating of any non-regular files.
Implies `--inplace`.
This special copy mode only works to efficiently update files that are
known to be growing larger where any existing content on the receiving side
is also known to be the same as the content on the sender. The use of
`--append` **can be dangerous** if you aren't 100% sure that all the files
in the transfer are shared, growing files. You should thus use filter
rules to ensure that you weed out any files that do not fit this criteria.
The use of `--append` can be dangerous if you aren't 100% sure that the
files that are longer have only grown by the appending of data onto the
end. You should thus use include/exclude/filter rules to ensure that such
a transfer is only affecting files that you know to be growing via appended
data.
Rsync updates these growing file in-place without verifying any of the
existing content in the file (it only verifies the content that it is
appending). Rsync skips any files that exist on the receiving side that
are not shorter than the associated file on the sending side (which means
that new files are trasnferred).
This does not interfere with the updating of a file's non-content
attributes (e.g. permissions, ownership, etc.) when the file does not need
to be transferred, nor does it affect the updating of any directories or
non-regular files.
0. `--append-verify`
This works just like the `--append` option, but the existing data on the
receiving side is included in the full-file checksum verification step,
which will cause a file to be resent if the final verification step fails
(rsync uses a normal, non-appending `--inplace` transfer for the resend).
It otherwise has the exact same caveats for files that have not grown
larger, so don't use this for a general copy.
This special copy mode works like `--append` except that all the data in
the file is included in the checksum verification (making it much less
efficient but also potentially safer). This option **can be dangerous** if
you aren't 100% sure that all the files in the transfer are shared, growing
files. See the `--append` option for more details.
Note: prior to rsync 3.0.0, the `--append` option worked like
`--append-verify`, so if you are interacting with an older rsync (or the