I see on the rsync man page that there are a number of delete options, but don't really understand the differences between them. What are the differences between these options?

 --del                   an alias for --delete-during
 --delete                delete extraneous files from dest dirs
 --delete-before         receiver deletes before transfer (default)
 --delete-during         receiver deletes during xfer, not before
 --delete-delay          find deletions during, delete after
 --delete-after          receiver deletes after transfer, not before
 --delete-excluded       also delete excluded files from dest dirs
  • 2
    Why --delete-before is described as (default)? I cannot understand what (default) means. – Marco Marsala Nov 4 '16 at 7:56
  • 1
    It's no longer specified as default in the man page for rsync version 3.1.2 protocol version 31. However, my guess on the version with the quoted text is that if you only use --delete rather than --delete-WHEN, then it's as if you specified --delete-WHEN where WHEN defaults to before. – Tom Hale Jan 14 '17 at 2:15
  • --del/--delete_during: Deletes files from the destination dir as they are copied (saves memory compared to --delete-before: --delete-before makes a separate scan to look for deleteables)

  • --delete: Deletes files in the destination directory if they don't exist in the source directory.

  • --delete-before: Delete files in the destination directory before copying file-with-same-name from source directory

  • --delete-during: Delete files in the destination directory WHILE copying file-with-same-name from source directory

  • --delete-delay: Mark deletes during transfer, but wait until transfer is complete

  • --delete-after: Receiver deletes after transfer, not before...If some other part of the rsync moved extra files elsewhere, you'd want this instead of --delete-delay, because --delete-delay decides what it's going to delete in the middle of transfer, whereas --delete-after checks the directory for files that should be deleted AFTER everything is finished.

  • --delete-excluded: Deletes files from the destination directory that are explicitly excluded from transferring from the source directory.

The point of rsync is not copying, it is archiving. This is an important distinction. Processing deleted/changed files is critical, and in many cases nuanced.

The --delete flag in particular is one I've seen screwed up many times. A lot of people use rsync to move files to low priority storage, and in this case you want the files you're moving to still EXIST in the destination directory. That's not what delete does: --delete makes sure that, when you delete a file from the source directory, it is ALSO deleted from your destination directory, so your destination doesn't get full of junk... Once saw a guy wipe out his backup by putting in a new drive, and not turning off his nightly rsync script. Script saw that the source dir was now empty, and it deleted every file in the destination dir, so they'd match.

Most of the other options are space or performance related. When you delete the files is important if you want to make sure the transfer is successful before you do anything, but if your device is too small to handle 2 copies of all the information, you need to delete as you go, etc. It's a little wacky because of its long history across multiple platforms: some options have been added so that people who were used to certain behaviour wouldn't be confused.

  • 3
    So is --delete and --delete-before the same? man rsync doesn't say when --delete deletes files. – ppr Jul 3 '15 at 15:07
  • @ppr: Depends on the system. The reason it has so many specific options is because delete on Solaris != delete on HP-UX != delete on AIX != delete on Linux. – Satanicpuppy Jul 6 '15 at 14:39
  • When rsyncing a whole directory, does delete-after delete each file in between syncing, or only after the whole dir has been mirrored? I thought delete-after was sufficient for my needs but i'm getting no space left on device when backup up one of my drives. – Sridhar Sarnobat Aug 3 '15 at 21:56
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    @Sridhar-Sarnobat: Either. It moves everything it's going to move, and when it's done, it's starts deleting things. If you want it to delete before it's moved everything, use --delete-during – Satanicpuppy Aug 4 '15 at 18:58
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    After some experience, I'm finding that even delete-during doesn't always prevent no space left on device (on Linux). So delete-before is the only guaranteed way to avoid it (like when mirroring a drive that is almost full, and the destination drive is almost full too). – Sridhar Sarnobat Jan 26 '17 at 22:58

There are two things going on:

  1. Who does the deleting
  2. When it happens

Either the sender or the receiver can be instructed to do the deleting (I'm not sure why this matters). So when rsync from one computer connects to the rsync server on the other side, this determines who is effectively issuing the delete command.

When it happens is pretty easy... before means all the files are deleted, and THEN rsync copies over the files. during means as it goes through the list of files, it deletes them when it comes to them, and after means it waits until all the files are transferred over and then deletes the remote side. This matters only when the transfer gets interrupted.

  • I'm pretty sure none of these options are related to deleting things from the sender's side. All of them (AFAIK) relate to deleting things from the receiver's side. Also, you say: "before means all the files are deleted, and THEN rsync copies over the files" — is this right? I'd expect --delete-before to delete only those files that needed to be gone, not all the files! But I guess it's possible that rsync deletes everything and then transfers over the "new" (possibly unchanged) data... – Quuxplusone May 15 '16 at 1:59
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    Ah, "delete from sender's side" is supported by rsync, but the name of that option is --remove-source-files. – Quuxplusone May 15 '16 at 2:02

One other point worth mentioning is that if your source directory ends with /*, then rsync will only consider those files and not the directory itself (and thus the absence of files that you want deleted on the destination).

If you're specifying a delete option above, but rsync looks like it isn't deleting, then check to make sure you're not accidentally globing and providing a list of files when you mean the directory itself.

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