newbie questions about clean install

Discussion in 'Mac OS X Lion (10.7)' started by sn, Jul 30, 2011.

  1. sn macrumors 6502

    Apr 22, 2011
    i don't really know about the ins and outs of computers but i've just spent the morning learning how to do a clean install of lion. i'm running it on my mbp at the moment but, like many others, am finding my machine to be noticably slower than when i was running snow leopard and am hoping a clean install will help.

    so i've re-downloaded lion, found the file called in the installer called "installESD" (the big one!), and used disk utility to create a bootable usb of it.

    now, from what i understand, the reason we see this slowness is basically because when we do an normal install, it just dumps the new os on top of everything that was already on the computer. but, by doing a clean install, it is clearing out the computer and starting afresh. this is why it's essential to have all your important stuff backed up. but my question is, how do i do the whole cleaning put the computer bit? in my head it seems pointless if i'm just downloading lion, putting it on usb, then putting it back on my computer. surely there needs to be a step in there somewhere to do the 'erasing my computer's contents' bit otherwise it's just dumping the new os on top of everything else again?

    i'm sure i'm missing something, just need someone to tell me what! sorry i'm so bad at this but any help would be truly appreciated.

  2. robgendreau macrumors 68040

    Jul 13, 2008
    If you don't know the ins and outs of computers, save yourself time and headaches by doing this:

    Make sure you have a good backup of everything.

    Run Software Update to update your system (assuming SL, of course) and boot from your original system disks and run a permission repair and disk repair on the drive you boot from, just to make sure everything's OK.

    You've already create a bootable Lion disk, so that's good.

    Then run the Lion installer. In other words, skip the "clean" install, which doesn't exist anymore. IF your computer screws up badly, either go back to SL, or THEN erase your drive and start over with a new install of Lion.

    The default method for installing Lion is via Apple's installer. They no longer offer a "clean" install of system software; that's a relic of days gone by. You can manually do an "erase and install," which basically means erasing everything and starting over with JUST a Lion installation. Then you have to either migrate your stuff over via Migration Ass't, or restore it from a Time Machine backup. Either method also has the potential for introducing errors, and I wouldn't recommend a novice do it.

    You don't need to remove every little bit of useless data or code from your computer. ANY method of moving to Lion is going to leave junk behind, and even if you bought your computer today with Lion on it some application you are bound to purchase is gonna leave junk around. Don't worry about it. If you are having trouble with something, or you suspect it won't work in Lion, then note it, and try the usual diagnostic methods to ferret the problem out. Check to see if the stuff you have is likely to work. And read this:

    In short, erasing your hard drive and restoring/migrating is a drastic solution to a problem you may not have. Try the regular install first; it took me about 35 minutes on a very full computer. It went fine, but if it didn't, I could always erase and start over, doing an erase and install manually.

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