How do I trigger rsync on file modification?

I can sync folders with rsync -avz /directory /target, now I wish to do it if I changed a file in /directory so rsync should be called automatically.

I am using Virtual Box and the shared folder of Virtual Box is really slow, especially if you have a webpage which is using the shared folder as document root. With rsync i would be able to work with my local files on shared folder and sync it automatically with document root.

I hope someone has an idea how to do so,crontab would be not good, because it is executed each x minutes, so if i don't do anything, it will still call rsync but not if I modified my file.

Best regards

4 Answers

crontab would be not good, cause it is executed each x seconds/minutes, so if i dont do anything, it will still call rsync but not if i modified my file

rsync will only sync the files that have been changed. If nothing has changed, it will exit. That's really a minimal overhead.

If you're unhappy with that you could use inotifywait:

while inotifywait -r /directory/*; do rsync -avz /directory /target
done

That will be more instant but it will do things every time you save.

6

You could use Lsyncd (Live Syncing Daemon):

Lsyncd watches a local directory trees event monitor interface (inotify or fsevents). It aggregates and combines events for a few seconds and then spawns one (or more) process(es) to synchronize the changes. By default this is rsync. Lsyncd is thus a light-weight live mirror solution that is comparatively easy to install not requiring new filesystems or block devices and does not hamper local filesystem performance.

Here is for example a tutorial for Ubuntu 16.04.

You can use inotifywait and rsync. inotifywait with the event modify,create,delete enabled. This way you will synchronize with your server only when the file changes, otherwise it will sync whenever a file is read (editors read several times your file to check if there are any changes). Thus said:

while inotifywait -r -e modify,create,delete /directory; do rsync -avz /directory /target
done

2

Expanding slightly on a comment to the accepted answer I've had success using fswatch to trigger an scp of changed files to the guest. On Linux this is a wrapper around inotify but it's also cross-platform (I'm on a Mac with an Arm-based QEMU guest). I've tacked on an ssh remote build as well. The push approach works well with shares that behave in less than ideal ways.

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