«But I thought YOU did the backups …»
After realizing it was more than three weeks since I last rebooted my MacBook Pro, I shut it down yesterday evening. Today, instead up booting up normally, it quit the startup process and went into some kind of update process. Strange, I did not install anything within the last couple of days. Even worse, the update failed. Exiting the error screen and rebooting led to the same process: login, quit startup process, starting to do an update and displaying the same error screen.
Probably the last thing you want on a lazy Sunday, esp. when you begin to realize that the last backup was a couple of days ago. Sure, there’s syncing to DEVONthink on my iPad, and some files were stored in other places, but it would have been very inconvenient if my data were lost.
On the bright side, the harddisk drive was still recognized and the data seem intact. I had harddisk drives die on me and that does look different.
Looking online via the first error message in the Installer Logs:
Apr 22 07:56:46 MacBook-Pro OSInstaller: The main OS Installer distribution (/Volumes/Macintosh HD/Library/Updates/AtomicUpdates/091-76232/091-76232.English.dist) did not load with error: The file doesn’t exist.
led me to this page, which in turn led me to a stackexchange posting. Looks like some files were left over from an earlier update process which have to be removed. In the meantime I had rebooted the Mac into safe mode by holding the shift key during the startup process. I had to hold the shift key for a very long time — it took ages to boot. But at least in safe mode, I could access my data again.
Before deleting files, I first did another backup of the most important files (the things I could not get back and — in part — had to stitch together from different sources). I then wanted to boot the Mac again without having deleted the files to document the error, but strangely enough, after being in the safe mode, it booted normally. Very very strange.
So, I guess I keep the info about deleting left over install files if this was really the problem. And at least the safe mode worked well to access the data.
Still, effective reminder not to neglect regular backups.