OS X Developer Tip: Slim Time Machine Backups

January 8th, 2009

Ray Drainville

If you’re using Mac OS X and you’re a developer and you’re too busy working to think about backing up your work, then Time Machine is fantastic & a lifesaver. Time Machine will automatically back up your work on an hourly basis. Coupled with a Time Capsule—which provides both the storage for those backups and your wireless connection—backing up is seamless, which is as it should be: if it isn’t seamless, you’re not going to back up nearly as often as you should.

However, Time Machine is not without its faults. I found it frustrating to set up initially, as I was setting up individual accounts (with passwords) & the setup for this is not clearly laid out. Worse, however, is that you can’t set up default rules—like ignore any directory named logs (those developing in Rails will know the files in logs can get huge), although you can set directories (or files) to be ignored manually.

Worst is the lack of any idea of what Time Machine is backing up. When you’re a developer, this can be very frustrating, as periodically you’ll find that you’re suddenly backing up gigabytes of data without knowing why. This is bad: when Time Machine runs out of space, it removes the oldest backups, so you can’t go “back in time” as far as you may need to. For instance, my last backup is 4 October when it should be something back in June, when I first bought the Time Capsule. Something was eating up space.

You could adopt a Zen attitude to this: let it do its thing, accept this state of affairs & doubtless you’ll be happier—until your Time Capsule is filled, that is. Or, you could be obsessive-compulsive & make yourself miserable trying to figure out wtf is going on. TimeDog helps you see something of what’s been backed up, but I found it unhelpful as it wasn’t letting me know about the latest backups—in my case at least, it only appears to give you information about the initial backup. Well, that’s not helpful.

Last night, however, the right chain of events occurred that provided the solution—for web developers, at least. I was performing a MySQL sync for one of my clients—in this instance, I also sync the database locally so I can check my work against the client’s actual data. Time Machine started up just after I started syncing locally. At first it was backing up about 2.5MB. Suddenly, however, it was backing up over 2GB worth of files. Strange, I thought—I had excluded the db folder on the Rails project, so the synced YML files shouldn’t be backing up.

And then it hit me: Time Machine was backing up the actual updated MySQL databases. Obvious, really, when you think about it. For Mac developers, your MySQL databases will be in one of two places:

  • If you’re using the default OS X setup, /var/db/mysql;
  • If you’re using MacPorts, /opt/local/var/db/mysql.

All you have to do to remove these from backups is to go to Time Machine preferences, click “Options…” & exclude the above directories.

You may want to prune more selectively, however: for me, the db sync only really affects one particular client. You can go into the mysql directory & merely prune out the database that’s filling up your Time Machine. Please note that this database won’t be backed up, however—you may want to back it up manually at specific intervals.

Posted by Ray Drainville Filed in Ray

3 Responses to “OS X Developer Tip: Slim Time Machine Backups”

  1. Nathan Fiedler

    Nathan Fiedler Says:
    January 21st, 2009 at 03:58 PM

    I just came across this myself. I have a snapshot of the production database, to use for development purposes (why? apparently it's too hard to bootstrap a development system for this project, sigh...) and found that Time Machine was backing up 1.5 GB every day. Using timedog (code.google.com/p/timedog) I found it was the MySQL ibdata1 file. Wow, holy crap! Every bit of data is in this one massive file. And when one single byte of that changes, Time Machine saves a new copy of the entire 1.5 GB.
  2. Ray Drainville

    Ray Drainville Says:
    January 21st, 2009 at 05:08 PM

    Nathan,
    I totally agree with you, it’s just insane that one byte will create such huge backups. Guess we can conclude that OS X isn’t using any cool schema!

  3. JDS

    JDS Says:
    February 19th, 2009 at 07:19 PM

    Timedog will show you the most recent backup by default, or alternatively any you specify on the command line. It’s new home is: http://code.google.com/p/timedog/

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