My Time Machine Exclusion List

A friend recently asked me about my opinions on the Time Capsule. I had the first generation device. It was OK, but slow, and eventually died the death of the power supply.

I have the latest gen now, 2TB, and love it. With 10.6 over a fast network, I don’t notice the hourly backups. One thing I did notice as time went on that the backups were getting kind of big. I want my individual machine backups to be under 1TB so I could archive them to some terrorbyte external drives I already have. I’d exceed that if I backed up too much junk too often.

My main goal for backups is to restore my $HOME data in the event of a machine failure. I don’t plan on restoring the OS or Applications from the backup. I’ll just use whatever OS is on the replacement machine or install my own, and I’ll install applications as I need them.

Backup Loupe is a great application for looking at your backups and seeing what’s being piggy. A file that’s only 50 megs is not a big deal, but it becomes a bigger deal if it gets touched regularly and gets backed up every hour. Using Backup Loupe, and general foresight, I have built this exclusion list over the last year or so. Unfortunately the list is not in any sane order. I’m not sure what order it’s listed, since it’s not chronological.

Some are pretty obvious:

~/.Trash – no need to backup trash.

/Library/Application Support, /Library/Caches and ~/Library/Caches, those will be re-created by applications. ~/Library/Application Support I do back up since it might have useful goodies.  [edit: Mark Aufflick suggests preserving /Library/Application Support/Adobe.  Personally I just use Lightroom and Photoshop CS5.  Lightroom is pretty well behaved, and I’ll just reinstall Photoshop.  But if you had the full Suite, that’d probably be a huge pain].

/Applications, I’ll just redownload and reinstall them.

/Users/bork is a test user I only use for development. No need to back that up.

The various parts peculiar to individual app or companies are there because they’re either big, can be regenerated, or an app touches a file often. Camino is one of them. I don’t use it very often, but every time I do I have to back up 50 megs. So its application support directory is on the chopping block. Similarly, Chrome gets updated every week, and is pretty big.

/Developer and /Xcode4 are there because I’d fill up the Time Capsule just from Xcode updates. I can always download the latest one if I’m setting up a new machine.

~/junk is a directory I use to throw junk into (hence the name). NoBackup is a similar directory at the top level. I have one in Movies too as a place to store one-off iMovie projects. Once I create the final movie the project can go bye-bye, and I usually don’t feel the need to back it up in the interim. I can get the original footage from the camera again. If it’s something larger or more important, I’ll leave it in ~/Movies, which does get backed up.

~/Downloads is another place for stuff I don’t want to delete right now, but won’t cry if it suddenly went away. If I want to keep it, I’ll put it somewhere that’s backed up.

Lightroom generates previews of photographs so that the UI is more responsive. Those can be regenerated later, so they don’t ned to be backed up.

All system files, including /Library/Printers,and /usr are things that would come with a fresh OS instal. Things in /usr/local I can re-install as needed. Same with /opt.

My music lives on another machine, so I don’t need to back up ~/Music

I check with Backup Loupe every now and then to make sure there’s not a new suprise that’s getting backed up.

Addendum: courtesy of brad@cynicalpeak, there’s other trash directories, /.Trashes, /Volumes/*/.Trashes if you have multiple disks.  Also /var/folders is yet another cache location.