time machine ML & El capitan

[lawrie1947]

(apologies for crosspost)
I have just upgraded to El capitan from Mountain Lion and all seems fine.
I created a backup on Time Machine before the upgrade.
If I do a backup now will it overwrite ML or still leave me the option to revert to ML if there is an issue?

 

[Weaselboy]

(apologies for crosspost)
I have just upgraded to El capitan from Mountain Lion and all seems fine.
I created a backup on Time Machine before the upgrade.
If I do a backup now will it overwrite ML or still leave me the option to revert to ML if there is an issue?

It will leave it for now. The TM works is as the destination disk starts to get full, TM will purge off old data. So at some point part of that "old data" will be the system files from Mountain Lion and it will be gone.

 

[insonias]

It will leave it for now. The TM works is as the destination disk starts to get full, TM will purge off old data. So at some point part of that "old data" will be the system files from Mountain Lion and it will be gone.

Are you sure that TM will not do anything to the old backups? I have the same issue .. I want to upgrade to El Capitan from Mountain Lion but I'm afraid that the new OS will mess up with the old backups. The only necessary thing to do is point the TM to the same disk upon the installation of the El Cap. ?

 

[Weaselboy]

Are you sure that TM will not do anything to the old backups? I have the same issue .. I want to upgrade to El Capitan from Mountain Lion but I'm afraid that the new OS will mess up with the old backups. The only necessary thing to do is point the TM to the same disk upon the installation of the El Cap. ?

It will just keep on using the existing backup set. That said, if you have the only copy of the family baby photos on there, I would make a second backup and set it aside just to be safe. But what I described is how it works.

 

[Rhinoevans]

I had to use a new HD for El Capitan TM backup. The HD that was used for the Yosemite for TM backup was not recognized by El Capitan and I think to use it as a backup I would have to reformat and select it as a new TM backup and lose the Yosemite backup. Not sure why I need the Yosemite backup anyway since I have moved on to El Capitan.

 

[Weaselboy]

I had to use a new HD for El Capitan TM backup. The HD that was used for the Yosemite for TM backup was not recognized by El Capitan and I think to use it as a backup I would have to reformat and select it as a new TM backup and lose the Yosemite backup. Not sure why I need the Yosemite backup anyway since I have moved on to El Capitan.

I went from Yosemite to El Capitan and the same TM backup just kept on running for me.

 

[lawrie1947]

Mmm, thanks for the replies. I had assumed that the TM would back up system files it recognised as well as apps and docs etc. Still not sure if I could reinstall ML once I have backed up with El Capitan...it has been a long day though. Appreciate the help

 

[Weaselboy]

Mmm, thanks for the replies. I had assumed that the TM would back up system files it recognised as well as apps and docs etc. Still not sure if I could reinstall ML once I have backed up with El Capitan...it has been a long day though. Appreciate the help

TM does backup system files as well as apps and all your data. With the exception of some swap and cache files, TM backs up the whole drive and can be used to restore to a new drive.

You can also use TM to restore to a previous OS version if that OS version is in the backup set. When you go to restore you will get a screen that looks like this example. See down there where you could pick a previous date with Snow Leopard 10.6 and restore back to that rather than the later Lion 10.7 version.... that is what I am referring to.

But eventually as the backup drive starts to get full, TM will start to purge off the older backups. So using my example here, at some point TM would purge off the July 29 and July 30 backups there and when that happens you would no longer be able to go back to Snow Leopard 10.6 from that backup set.

Make sense?

 

[Ebenezum]

I wouldn't use the same Time Machine drive for backups if you want to retain the option to downgrade to previous OS.

In theory Time Machine should be able to return to previous OS even if its used for newer OS but in my experience it's not quarantined to work. I learned this the hard way when downgraded friends Mac from Yosemite to Mavericks, restore took a long time and eventually failed. Its possible it was due to changes in Core Storage between Mavericks and Yosemite (hard drive was fine) but I was not impressed. I was able to restore everything manually but that experience didn't improve my confidence in Time Machine. I had similar experiences with some of my clients Macs and I am not convinced that Time Machine is best way to downgrade to previous OS.

I recommend making a clone of your Mac with Disk Utility, SuperDuper or Carbon Copy Cloner to external drive before upgrading to new OS. Compared to Time Machine it's much faster and more likely to work when downgrading OS.

 

[NoBoMac]

What Weaselboy has been saying. But REALLY what Ebenezum said.

Before I do an upgrade to any version (major or minor release) of OS X, I make sure I have a clone of the version I'm going from, in case I need to restore back to that for some reason. As part of my usual monthly maintenance procedures, I make a clone of the drive, so at worst case, I've got a several week old clone to restore from, and probably can be able to restore the files in my user account from TimeMachine, to get the most recent versions of things (I have two TM drives, that I swap every two weeks, and on one of them, I've partitioned it such that I can also do manually copies of files every week, in case the TM copies are corrupted).

 

[dianeoforegon]

Adding to NoBoMac's advice to create a clone backup. If you don't have a clone backup it's time to start. Just like a seat belt and an air bag protect you in different ways when driving, you need both Time Machine and a clone for full protection.

Create a Clone backup:

A clone is an exact bootable copy of your internal drive. Unlike standard copying of all files to another drive, the clone software copies hidden files along with other in-use files that are not available when you copy over files to another drive.

Time Machine is not bootable on older versions of OS X. You could only restore from Time Machine unless you have a newer Time Machine that is now includes a recovery drive that is bootable. .

Software used to Clone:

SuperDuper! http://www.shirt-pocket.com/
CCC http://www.bombich.com/download.html

 

[lawrie1947]

Much clearer and appreciated. I have an old drive I can clone to. Thanks I also understand how TM works.