Questions regarding upgrading to ML

Discussion in 'OS X Mountain Lion (10.8)' started by MBAir 2012, Jul 25, 2012.

  1. macrumors newbie

    Hello guys,

    Couple of quick questions. My laptop came with Lion 10.7 and I'd like to keep a fresh copy of the OS as well as the new ML, i.e just the OS's (not time machine back up) How do I do this? From my understanding ML will download and start installing straight away? How long does the upgrade take?

    I plan to back up my Lion 10.7 (Time machine) before doing the upgrade however once ML is installed and I run time machine again will it erase/over write my old back up? Do I need to keep seperate back ups?

  2. macrumors demi-god


    I don't understand your question exactly... but if you want to keep a bootable copy of Lion around, you'll need to host it on an external drive. Time Machine will happily continue backing up your data, and will back up changes only, just like it did for previous OS upgrades. The upgrade process time depends on various factors, but I can break it down into 2 groups that are different enough to warrant separation: HDD-based Macs (25-45 minutes is typical) and SSD-based Macs (MUCH faster on this side - 15-25 minutes).
  3. macrumors newbie


    Thanks for the reply. Sorry if I wasn't clear, new to Mac OS:cool:. My question is basically how do I keep a copy of the OS on say a disc or usb/HD since they are downloads?

    I'm still a little confused as to how Time Machine works. Does it reinstate everything back to how it was to a certain point including the OS or is just the files/system settings? For example I want to keep a copy of my Time Machine back up of Lion just incase I want to go back to it. If I start doing a back up after I install ML will it not chage the OS from Lion to ML on the backup or does it only back up the files/settings? From what I understand from your reply if I wanted to go back to previous OS, I'd need to install the OS again and then "migrate" my files/settings as apposed to using the backup to go back to how my system was before I upgraded? I have to clone my system if I want to achive this, right?

  4. macrumors demi-god


    Oh, that can be done. The way you do it is this: Once you have the installer, quit it if it starts automatically. Control-click the installer in Finder and choose "Show Package Contents". Drill down through Contents and Resources. You'll find a large file called Mac OS X Install ESD.dmg. That's what you burn to a disc/USB drive.

    As for your Time Machine question, it saves everything except for cache files, which the OS will recreate anyway. This means that it is in fact possible to revert your system to the state it was in when a given backup was made. However, the Migration Assistant tool will only let you restore the NEWEST Time Machine backup.

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