What can make OSX reset to a fresh install?

[Caribayou]

I have a macbook pro 2.33ghz running 10.5, which I've set up as the same system I use at work for convenience' sake. It's not an important use machine, but comes in handy to make sure anything I discover at home that's useful will also work during the day. In the last year I've installed CS3 and 5 on it and built up a decent copy of my work Mac.

Yesterday afternoon at work I copied a few files to the MBP, closed it to sleep it, and came home. An hour after getting home I opened it up and it'd turned off (not so unusual, the battery isn't great on it), but it booted straight to a fresh install and first boot request for account creation.

EVERYTHING I'd ever installed on it is gone. It's a fresh brand new install of 10.5. No mail, no apps, none of my files, all of it's disappeared - there's no evidence it was ever a used system. What's happened here and how can I stop it happening again? I've lost access to about two gig of files I'd like to have looked over this weekend.

 

[mentaluproar]

iCloud wipe?

 

[benwiggy]

A common problem on early versions of OS X was for the user account to be renamed. On the next boot, OS X would not find the original names user account, and so create a blank one. This would give the impression of all files being "deleted", default settings, etc., etc.
If this has happened, you just need to check the /User folder and see if there's another User account. All your files will be there.

However, it's more worrying if you say that installed Apps are missing from /Applications folder, (assuming you installed them there and not in the user account Applications folder, which is possible but unlikely.) And if it started up with the initial "Welcome to OS X" and Setup program, then that's a problem. There is a little file who presence stops the initial setup app from running. But the only was I can think for files gone; apps missing and setup app starting is if someone has done a clean install.

Do you remember roughly how much space was used on your hard drive? Is it the same, or less? Can you find any with Spotlight?

Secondly: how can you stop it from happening again? Keep a BACKUP. Apple make this SO easy with Time Machine. TM has been in OS X since 2007, yet still we see people with no copies of their files.
If you don't have copies of your files: you will lose your files. I'm afraid it's as simple as that.

 

[Caribayou]

That was my first thought, that my user folder was renamed or corrupted, or some other big parts of the OS were missing - the first place I looked for my files was in /Users - but there's no evidence of them there. The MBP has a (pretty small) 120GB drive and had a little over 100GB used before it reset. Now it's under 10GB. No file on the HD bar a few logs & caches, and anything involved in the creation of one new user appear to be dated past the middle of 2009.

(I've lost a user folder once before when I ran out of space on an earlier iMac with 10.2 or so, so that lost-user folder symptom is familiar)

It *is* precisely like the MBP had an erase and install on the trip home.

I can recover with time machine certainly, but the time it takes to do that is still time lost, and the files I carried home on the machine are still inaccessible until Monday - backups as I have them set up don't solve the inconvenience here, alas.

 

[benwiggy]

I can't think of any method or circumstances where OS X would, of its own volition, be able to restore itself to a clean install without significant user intervention.

I would certainly verify the integrity of the disk.

I can recover with time machine certainly, but the time it takes to do that is still time lost, and the files I carried home on the machine are still inaccessible until Monday - backups as I have them set up don't solve the inconvenience here, alas.

If you have backups, then all is well, and you can restore your files and apps.
If there were files that you transferred from work which are not on your backup, then there's not a technological solution to that. Short of going back into work to get them.

You may wish to think of an improved method of backing up and of transferring files from work, to avoid any losses in the future. Hard drives fail, files get accidentally deleted, laptops can get stolen, etc, etc. You should expect these things to happen and prepare to cope with it.

I would certainly be very suspicious of this drive's reliability from now on.

 

[Ledgem]

iCloud wipe?

A good thought, but OS X 10.5 didn't support iCloud.