Does rsync delete unmatched files by default?

[Lennart Sorensen]

On Mon, Jan 03, 2011 at 10:12:20PM -0500, Kevin Cozens wrote:
> I haven't used rsync very often but my observation is that it copies  
> changed/new files *before* it does the deletion. Normally, this is fine 
> but if the target drive does not have a lot of spare space on it you run 
> the risk of filling the target drive when rsync copies the changed/new 
> files before it gets around to deleting files that no longer exist on the 
> source drive.

Actually it often deletes first (or along the way), at least in newer
rsync versions.  --delete-after explicitly makes it only delete when
all other stuff is done.  Without that option, it makes no promises
about when it will do deletes.

Essentially, --delete means --delete-during on rsync version 3 (when
both ends is version 3), since it does incremental file list transfers.
Older versions always sent the full file list first before doing anything
else (which was a lot less efficient), and on those --delete meant
--delete-before, so it always deleted fiels first.  If you want the
old behaviour back, use --delete-before, but you loose the advantages of
incremental file list transfers.  If transfering locally to an external
disk, that is probably not a problem.

-- 
Len Sorensen
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