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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

moon.musick
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BlackScorp
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4 Answers4

25

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.

Oli
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    well the problem it seems, that inotify is not able to check shared nfs folders. to make sure, what i want to,tryin to describe i have virtual box installed with vagrant, there i have a shared folder "projects" it is mounted on boot, all my webserver files are located there so i can modify them on my host system(win7) as i told virtual box shared folders are really slow, so solution could be to sync the mounted nfs folder to another place e.g /var/www but the common ways are not working, i tryed fileschanged, icrontab, gues gamin or fam would help, but i dont know how to start or use them – BlackScorp Aug 30 '13 at 10:55
  • @BlackScorp realistically you're stuck with just cronning rsync and letting it decide what needs syncing. As I lead with in the answer, that's not an awful bad option. – Oli Aug 30 '13 at 13:15
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    The other option is to push the files from the host rather than trying to detect changes remotely. – Oli Aug 30 '13 at 13:16
  • well this solution i used before, it has 2 problems: 1) i had to reconect everytime to my virtual box to edit files, which means, my virtual must running, quick editing is not working anymore 2) i dont know why, but because of the project scanning process of my IDE(Netbeans) samba shows 99% CPU Usage and everything within the virtual box is just slow while developing i will try the rsyn + cronjob solution or the php build in webserver – BlackScorp Oct 22 '13 at 06:29
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    The `inotifywait` solution has one slight but important drawback: it does not detect changes which happened when `rsync` is running. Consider the following situation: file A is changed; rsync is triggered; when rsync is *almost* done synchronizing file A, file B is changed. Now, `rsync` finished and `inotifywait` is running, but file B is **not synchronized** and won't be synchronized until some next change. **Consider using `lsyncd`** as suggested by @Arigion. – MarSoft Jul 25 '19 at 13:54
  • this will re-apply all events on all files after each change... and when it's applying it won't see any change in that period... – Somebody Nov 27 '19 at 10:19
12

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.

Arigion
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6

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
silgon
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    This won't detect changes happened while rsync is running. Consider using `lsyncd` as suggested by @Arigion. – MarSoft Jul 25 '19 at 14:00
  • this will re-apply all events on all files after each change... and when it's applying it won't see any change in that period... – Somebody Nov 27 '19 at 10:19
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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.

Robin Macharg
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