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qodeninja
Asked: 2011-12-06 16:29:13 +0800 CST

How can I automatically sync files on my CentOS VM?

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I have to keep copying files over from my ~/src to /home/httpd directory, which is a pain when I'm making front end changes. Is there a way I can have changed files sync automagically? -- and specifically only while I'm developing -- something I can turn on and off.

cron rsync

3 Answers

  1. I am not entirely sure what your objective is, but a few suggestions that might be of some use:

    Instant, on modification (save): If you want the files to be updated as soon as one is modified, I might ask why you don't just make your changes in /home/httpd and then once everything is to your satisfaction copy them back. The idea of a working directory for safeguards (or to prevent taking down your site with a bad edit) is negated if the changes are to be copied immediately.

    Near-instant, on modification: If for some reason, you wish to have your changes applied nearly instantly, on file modification (i.e. as soon as a file is saved, it gets copied over) then I would suggest looking into incron. It can be set to trigger a script when a directory changes.

    On demand (not instant):

    If you are looking to complete all your edits and then push the changes (which is what I expect you are looking for), then you have several options. I presume that the annoyance lies in determining what files were changed, and copying them from a variety of different directories.

    Shell script: One simple solution to this is to use rsync. It will determine what the changes are in your ~/src directory relative to your /home/httpd directory, and make the changes needed to get your /home/httpd in sync with your source directory.

    Version Control: The most effective solution, although, considerably more complex than rsync, is version control - for instance, Subversion. Basically:

    • Create a repository on your server
    • Import your files into the respository
    • Check out a working copy to /home/httpd
    • Setup a post-commit hook that will update /home/httpd
    • Check out a working copy to ~/src
    • Make your changes and commit them to the repository (svn commit) - the hook will automatically update /home/httpd

    While more difficult to setup, initially, this approach allows the greatest control, and will easily let you rollback changes, list the modified files, and see what changes (diffs) were made at each revision - you can also add a description to your changes with each commit.

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  2. Best Answer

    Although not automatic, once you are done doing modifications, use rsync:

    $ rsync -r --delete /home/username/src/ /home/httpd

    You could even create an alias:

    $ alias sync='rsync -r --delete /home/username/src/ /home/httpd'

    As I emphasize to everyone, before using this you should check out man rsync for additional options.

    Also, I'd strongly suggest version control (svn or git perhaps) for a multitude of reasons.

    Edit:

    What I would personally do is use a bash loop---specifically while loop with a sleep. Enter the following in the shell:

    while true; do 
    sleep 300 # Every 5 minutes
    rsync -r --delete /home/username/src/ /home/httpd
done &

    This will make it a background job that you could kill at anytime. Just type jobs to see the index of the job and, when you do not need it anymore, type kill %(index).

    Alternatively, to add the command as a cron job for, e.g., every 10 minutes, append the following to your crontab:

    */10 * * * * rsync -r --delete /home/username/src/ /home/httpd

    To edit your crontab:

    $ crontab -e
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  3. Look at lsyncd. It uses inotify to get info about changes in files and sync them over rsync.

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