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Time Machine: Mount backup disk on demand
Authored by: syzygies on Jul 22, '10 06:25:38AM

TimeMachineScheduler looks like a nice alternative, if one prefers GUIs and doesn't care about seeing source code. Many of us use Mac OS X Hints as a source of information for how to do things for ourselves; this is a matter of personal preference.

It is interesting that TimeMachineScheduler lists unmounting as a known problem; I had to tweak my script to get unmounting to work reliably. My observation is that there is an unpredictable lag after backupd stops running, before the OS realizes that the TM disk is no longer in use. My script waits, and gives this eight tries. According to my logs, I sometimes need the second try, but never more.

I didn't know about making volumes invisible to avoid dialog lags. Nice idea. I still prefer my backup volumes to be unmounted except in use. Safer, and saves a step when swapping disks.

OS X long ago (as of 10.4) stopped using cron jobs in favor of launchd. However, setting up a manual launchd job is more work than dropping a script in /etc/periodic/daily or creating the parallel /etc/periodic/hourly. If one objects to all periodic jobs on principle, just turn off Time Machine; it's an periodic job, after all. Perhaps my hint is most useful as an example of how to use /etc/periodic/daily or /etc/periodic/hourly, the quickest in-and-out for setting up a periodic task.

Time Machine is only part of my backup strategy; I also rely on a similar script to handle SuperDuper! backups. This avoids their GUI, manages automounting backup volumes, and suppresses error dialogs for unavailable volumes. I can list every conceivable backup dependency (e.g. backup "Media" to "T-Media" if "Media" and "T-Media" are available to be mounted) without ever seeing a SuperDuper! error dialog for unavailable volumes. Before this script, I used to see dozens of these SD! dialogs over coffee each morning. I've tried nudging SuperDuper! in this direction; their pre- and post- scripts won't run if the backup volume isn't already mounted. They have a very active user community who are happy as things are, and they are justifiably very conservative about making any changes that would impact the support needs of users.

The latest builds of rsync do a great job of preserving metadata; for many purposes one could replace SuperDuper! by rsync. I haven't bothered. I'm thrilled with how well SuperDuper! does the part of the job I still let it do.

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Time Machine: Mount backup disk on demand
Authored by: gvitale on Jul 22, '10 07:11:09AM

How do you tweak the TMS unmount procedure? What is the "my script" you mention?
Thanks in advance

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Time Machine: Mount backup disk on demand
Authored by: crarko on Jul 22, '10 07:19:00AM

The script in the hint; syzygies is the author.

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Time Machine: Mount backup disk on demand
Authored by: gvitale on Jul 22, '10 07:32:43AM

Thanks and sorry, I didn't realize you were referring to the hint' script, I though the comment was about TMS.
Automatically unmounting the TimeMachine Volume is also beneficial if you set the computer to hibernate, and is very unfortunate that TMS doesn't do it in a predictable way.
I'll give a try to your strategy. Thanks for the hint.

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