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Thu, 21 Sep 2017

Time Machine Backups

— SjG @ 3:37 pm

I use Time Machine for my local desktop backups. It’s a nice solution. It sits there quietly backing stuff up, keeping multiple revisions of files, and even keeping it all encrypted so if the external drive gets swiped it’s not going to be easy to get at the data.

Of course, it’s no substitute for a revision control system for code, nor is it good for situations where the office gets annihilated due to stray meteorite or drone strike. It’s not a complete solution, but it’s part of a broader collection of solutions.

Today I was reminded of some of the limitations. I used Time Machine to migrate to a new machine. That’s a pretty sweet process. You wait for a few hours of disk read time, and suddenly a new machine is populated with all your old settings, applications, data, and so on from your old machine.

But I found some things that weren’t quite right. Most of them had to do with processes that keep open files or databases, and don’t get backed up in a clean fashion.

  • Interestingly, Safari didn’t propagate Ublock Origin, which was a manually-added extension. This was the only surprising one of the bunch.
  • MySQL databases. I hadn’t shut down the MySQL server when the backup ran, so the table files from the Time Machine restore were corrupted. I was able to copy the files off the old machine (after shutting down mysqld gracefully), and use those.
  • TimeKeeper‘s datastore files were all corrupted. I had to delete them, and re-export/import the data from the old machine.
  • VMWare Virtual Machines. I knew they’d get corrupted if backed up by TimeMachine for the same reason as the above, but then I forgot that they weren’t backed up. I had to manually copy them off the old machine. This reminded me — if I want backups of my VMs, I need to do it myself!

That’s all thus far. Nothing too surprising, but a good reminder. Just because you’re backing up, doesn’t necessarily mean you’re backing up stuff in a restorable state!


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