How to Clean Install OS X Mountain Lion
Though most users are best served by the easy upgrade process to OS X Mountain Lion through the Mac App Store, some people want to perform a clean install and start with a blank slate. A clean install means the drive is completely erased and Mac OS X 10.8 is installed fresh, nothing else is on the drive, no apps are installed, and no files are included.
The process described below will format the selected Mac disk and erase everything on it, followed by performing a completely clean and fresh installation of OS X Mountain Lion.
We’d highly recommend backing up your Mac before performing a clean install, even if you have no intention on using it afterwards.
- If you don’t have it yet, get Mountain Lion from the Mac App Store but do not install it yet (or redownload it if you did install it)
- Create a bootable install drive for OS X Mountain Lion, make one manually with a USB drive or use the LionDiskMaker tool to automate the process with a USB or DVD
- With the boot installer drive connected to the Mac, reboot and hold down the Option key
- Choose the “Mac OS X Installer” startup volume from the boot menu
- Select “Disk Utility” and choose the hard drive you wish to format, click the “Erase” tab, and then pull down the “Format” menu and select “Mac OS Extended (Journaled)” as the type, name the drive if you wish
- Click the “Erase” button and let the drive format – this is the point of no return
- When finished, quit out of Disk Utility and now select the “Install Mac OS X” option from the menu
- Choose your freshly formatted hard drive and install Mountain Lion
When the Mac reboots you will have a clean installation of Mac OS X 10.8 to work with.
At this point you can either import files and apps from the backup you made, manually copy over backed up files, or just start anew.
I have a clean mac book pro which mean no operating system on it. How do I install OSX Mountain Lion V 10.8 on it.
I have the OSX Mountain Lion V 10.8 installation disk.
It is not bootable since I try pressing option key when the Mac book restart and it didn’t show anything.
Any advice? Pls help.
I recently received a mac book pro from a friend of mine. I decided to clean install OS X mountain lion to make sure there was no left over stuff from the files she had on it. Now when i turn the computer it give me the option of re-installing the software;
I click continue and it says contact apple
Am i able to make OS X flash drive installer without the mac? (My other computer is windows)
Thanks a million :)
Hi,
I may have a few silly questions but here goes:
I’ve never performed a clean install before, and am running mountain lion at this moment. I want a clean install because my mac is a little slow..it’s a pro from 2009 – and I just feel it is time. also I’m sure there’s a ton of stuff on it I don’t need – that I’m unaware is draining my mac.
Just wanted to ask (as someone who’s never clean installed before)
1. when I back up do I just copy applications folder, docs and anything I know I want to keep?
2. or will the timemachine back – up be enough? Will that be the easiest way?
I’m getting a 3TB external hard drive, so I figure that will be enough.
Also I have a few games on there Sims 3 – tomb raider and the likes – also sims midieval which I downloaded from online store. If I coply applications or use timemachine,will I be able to recover this after the clean install?
If I follow the above instructions to a T…will I be in good hands? There is no way I can mess it up?
Thanks so much
Well no where did it say it was gonna take 6 hours to download!!!!! Now I’m left without a computer!
It does somewhere.
Welcome to the land of the third world internet.
I saw that the file was almost 5G so I went to the
UMC @ CU Boulder to download. Took no time at all.
Are you near an internet backbone facility with public access?
Find one and use it for large files.
I would like to do a clean install of 10.8 but i have one question–besides my main mac hard drive in my mac pro i have 2 other bays in a raid for my iTunes library. will the clean install mess up ‘seeing’ my Striped RAID set???
Two questions.
1. What will happen to my Boot camp partition after a clean install of Mac OS X? Will I still be able to boot windows normally?
2. What happens to programs that requires license to install, for example Office 2011, Photoshop CS5 etc? Will they allow me to restore it from TimeMachine backup or do I need new licenses?
I had to boot and hold down Command+R to get in and reformat the new drive, etc. this may help someone…
Ben,
Long answer so google for each program.
I just copied the correct folders for iTunes, Mail, iPhoto etc. and placed them in the exact spot. Mail was the trickiest.
After doing a clean install what’s the best and easiest method for putting my old files, photo’s, music and app’s back onto my Macbook Pro from my external Hard drive
Well I highly recommend a clean install – I bought a MacBook Pro 2011 with snow Leopard, upgraded to Lion, then to ML. Running pretty sluggish, so did a clean install – its like having a new mac!!!! Did take 6-7 hours to reinstall everything though
I just install an additional SSD hard drive into my late 2007 Mac. I wanted to put a new copy of MAC OSX lion but my DVD player was set to a wrong region, USB drives wouldn’t work so I decided to download it from Mac.
Before I did that I partitioned the drive and then shut down the computer and then held command R untill I could download from the Apple store. Then I downloaded and it restarted but it wouldn’t install. I restarted it a few times but nothing.
So then I tried to reset the PRAM by holding down command, option and P and R. This chimed twice and I let it start up. Then I was still not installing.
I then tried command R one more time and then it started to install. Seems to be the only and no one else talks about. I even read that someone said that it cannot be done without a bootable USB.
Work great and thanks, instaling my osx now :D
Why in an upgrading to Mountain Lion, background desktop dones’t changed, as clean install, in clean install background changed to a new Mountain lion galaxy
Please reply
There is an incredible difference with a Clean Install to speed and stopping the spinning beach ball that arrives after about 2 to 3 years on a Mac.
When the OSX came on DVD, there was an option for Clean Install which did NOT delete your entire Hard Drive and kept all preferences intact.
It seems now that the new OS’s come from the Applications Store the only way to do a Clean Install is to delete the entire target drive and install the new OS and reinstall all apps and preferences.
This will take about 5 days as opposed to 2 hours. Steve Jobs would turn over in his grave!!!
Is is useful to make a clean install? I mean has anyone really noticed a diffrence?
Thank you
I bought used macbook 4,1. it has win 7 on it. i want to install OS x lion.
Please let me know the process.
Question: I am selling my mid 2011 iMac that was pre-installed with Lion. I recently upgraded to Mountain Lion. Will I be able to make a Mountain Lion installation disk to reinstall it fresh for the new owner or will it reject their Apple ID once they complete registration? (since I purchased Mountain Lion through the App Store…)
Thanks!
This was very helpful. Thanks for publishing. My 2009 MacBook Pro Snow Leopard was a good computer, but it was just running too slow. Wiping it with a clean install of Mountain Lion gave it new life.
I used the USB boot and it worked like a charm (once I found a large enough USB).
I am happy Mac is bailing on the DVD. Even though it cost me a bit more effort, its one less piece of trash in the dump.
I made a bootable cd on my MBP and used it to do a clean install on the same computer and it worked perfectly! now im using the same cd to install ML och my imac but when it’s installing it says that ” can’t download the additional components needed to install mac osx” is it just because i made a bootable cd from another computer or whats happening? i did a clean install and iv already removed everything on my imac so i can’t really go back :( what should i do?!?!
You ever get it fixed? If so, can you tell me what you did.
My luck, I have a bootable MT Lion USB, but it won’t take and I have to download Lion all over again….
Hi!
I made a clean install of ML on my new SSD drive and I’d like to re-install all Apps purchased from the App store. How do you get the apps again? it say’s it is installed.. is it because I still have my My OLD HD[with ML/upgrade from Lion] internally? it is still present.. i moved it to my superdrive bay[datadoubler]. i plan to slowly move to the ML in the SSD drive once all apps are re-installed. any info is much appreciated.
Same problem here. AppsStore does not let me reinstall the apps! It says already installed. For some it says that they have updates. I run the update but the apps is not present :-/
Fresh installs are pretty straight forward… but I don’t think many people are aware of an interesting point that ‘JJ’ made about doing a fresh install and how it affects the download/update status of the Mac app store – this is an important topic to discuss so can someone please shed some light on “JJ’s” original post…?
“JJ says:
July 27, 2012 at 3:34 am
Hi. I followed the article and did a clean install. But now when I go to the mac app store and check the mountain lion app, it says “download.” But the thing is, I’m already running it…So even if I do click the download button, it gives me a prompt saying “OS X 10.8 is already installed on this computer. Are you sure you want to download it?” So I’m just wondering whether this will affect me from updating ML when the updates are released, as other purchased apps say “installed” instead. And if it does affect future updates, how would I go about fixing this?”
no it will not
I have a late 2008 MacBook Pro running Lion that I want to upgrade to Mountain Lion. Thinking of a clean install and restoring programs and data from my Time Machine back up. Is this possible and if so, how?
Hey I have a question. I upgraded my snow leopard with Mountain lion however it really slowed down the boot of the computer. So I am actually thinking of making a back up of my files with time machine, then clean install mountain lion and finally put the backup to get my files. Is it a good idea?
I mean i worry that by using my backup I will also retrieve the causes of why the Boot is slow. Can anyone help?
I’ve just made a ‘Mountain Lion Recovery Flash Drive’ and have just cleared my HD in Disk Utility after switching my Macbook Pro (Mid 2011) off and on again whilst holding the option key down. When I click “Reinstall OS X”, and agree to the Terms and Conditions, my Macintosh HD doesn’t show up, only my recovery flash drive which is locked. What do I do from here?
try running disk utility first, and make sure there’s a Mac formatted partition on the drive. It could be completely blank.
How long does it take to clean install mountain lion, coz i did create a bootable usb and still its downloading again ftom the web when i install it
can I just put the new ssd I ordered into my MacBook , boot from the original one in an enclosure, format the new one and buy and install mountain lion on the new ssd, then worry about migrating anything I want…start completely new?
I downloaded Mountain Lion from App Store on my MacBook Pro. Then had my wife log into App Store using my login and then downloaded the already purchased Mountain lion on my iMac at home. Afterward, the computer ws completely reset ike from the factory. She is devastated and I am in the Navy and on the other side of the world and can’t help her. Can someone please help?
Contact the Apple Store, make an appointment with the Genius Bar, if possible.
im new to this when I upgrade to mountain lion does apple send you a key or does it just go over the top of leapard.
thanks for the answers in advance
Hi guys, first time on a forum!
Quick… but not so simple question: Will a clean install delete my original recovery partition?
i bought a macbook pro last year with Lion installed… so the recovery partition contains Lion. Now, i dont want to lose this kitty and would like to keep it handy (like for when the time comes to sell my Mac, ill want to wipe it clean and avoid giving free stuff, for example: a mountain lion installation!). Long story short, i want to be able to de-evolve from mountain lion to lion.
does anyone know what happens? does the installer wipe the COMPLETE hard disk drive or does it wipe the PARTITION to be used?
thanks in advance!
Hello! Please help me!
I created a USB stick with Mountain Lion Disk Maker, just as you described and deleted my Recovery Partition.
Then I restarted my Macbook Air (with Lion) and pressed ALT. I chose the USB to boot from. Then I erased my partition on the SSD and started the installation. Unfortunately I quit the installation and wanted to start the procedure again.
When I booted the USB once more it automatically started the installation but with an immediate error: “Installation abortet, start again”.
Disk utility shows 12 untitled drives (I think the recovery partition was started). How can that be?
Please help me!
Maybe the internet recovery (cmd+R) will help?!
Format the drive, delete all the partitions, and start over.
In the future just stick with upgrading for the easiest time.
Worked with cmd+R (new install of lion).
Today I will install ML with USB stick.
Does it reduce the speed of a SSD to reinstall OSX some times?
Hi,
From a Mac Book Air (mid-2011), when you wanna do a clean install, Lion is downloaded directly on the apple’s servers. Because the laptop doesn’t have a CD/DVD slot.
If we buy Mountain Lion via the AppStore and then we perform a clean install as we do normally, will it be Lion or Mountain Lion that would be downloaded ?
Hi,
I really would appreciate any help I can get.
I have an iMac 3.2GHz. I’m on 10.6.8 and I want to upgrade to Mountain Lion. BUT – my hard drive is so full, my iMac doesn’t like it so broke down. I booted from a backup external hard drive. But I really want to have a clean and tidy hard drive. What I want to know is this.
Should I wipe clean my iMac and restore from my hard drive. Afterwhich, I can download Mountain Lion and upgrade from there
Or is there a way to clean my iMac and install Mountain Lion straightaway and simply drag and drop what I want from my external hard drive onto the new desktop.
I hope that makes sense.
Oh and what about my settings, Safari bookmarks etc
Thanks
G
About the mouse click issue: For those who’ve become accustomed to tapping the trackpad instead of actually clicking on the mouse buttons, remember that tapping the pad doesn’t work during installation. It works only after you’ve entered Lion or Mountain Lion and have set up your trackpad preferences. Until you do that, you need to CLICK on the mouse button. Respond if this helped you out!
I have now deleted the original partition. When I go into Boot to install a fresh copy my trackpad doesn’t work… The mouse moves but won’t click on anything. I can use the keyboard up until I get to the choose hard drive screen, but once I tab to my hard drive, there is no way to tab or get to the continue button. I have been searching for hours and can’t find a fix for this!! Can anyone help?
Maybe I missed it, or maybe it is actually not necessary, but I have not seen any of the ML “Fresh Install” guides tell you to deauthorized your machine from iTunes before doing the fresh install.
Is that no longer necessary?
MotionMan
I have a 2010 MacBook Pro running Snow Leopard. I also use Boot Camp for Windows 7. If I do a clean install, will I lose the Boot Camp partition, or does the formatting leave the Boot Camp partition alone?
Thanks
Tried a clean install. But during install, mouse click on track pad doesn’t work and tabs don’t work as they are supposed to. Unable to install. Anyone found a fix.
I have this same problem. Have you found a fix?
I used a USB mouse to overcome the problem
Me too, have tried recreating the install disk and formatting the drive, no joy.
Hi. I followed the article and did a clean install. But now when I go to the mac app store and check the mountain lion app, it says “download.” But the thing is, I’m already running it…So even if I do click the download button, it gives me a prompt saying “OS X 10.8 is already installed on this computer. Are you sure you want to download it?” So I’m just wondering whether this will affect me from updating ML when the updates are released, as other purchased apps say “installed” instead. And if it does affect future updates, how would I go about fixing this?
did clean installation but stuck on blue indicator then rebooted now i cant install anything on eventhough i try to reinstall 10.7, it keeps saying “There was a problem installing Mac Osx” Try reinstalling…anyone have the same prob..
I have no option to erase my primary hd in disk utility to do a clean install. How do I accomplish this?
You can’t erase the disc from where the disk utikity is located (if you are booting from the recovery you wont be able to do it because the recovery partition resides on the same disk). You had to create a separate startup disk (can be DVD, pen drive or just an external HD) startup from it and erase the internal HD.
I have created a USB boot disk and I’m trying to do a clean install. When I reboot my system and get into disk utility to erase my primary drive the options and disable in order for me to complete the task. How can I accomplish thus?
so what happened?
While trying to erase your default startup disk, if you don’t find the option to erase, click on the unlock option to unlock your drive with your system password and then continue as mentioned above. Cheers.
Will this method generate the recovery partition during the clean installation?
Yes, all variations of installing Mountain Lion through the installer app will create the Recovery Partition in the process.
FWIW, these days once I’ve done a clean install, I image the drive with carbon copy cloner (my favorite, but there are other utilities out there) to a .dmg file. That way if I have to redo the installation, I can just blast the image unto a blank HD. So my basic procedure is:
1) Prep clean install
2) image disk
3) use migation assistant to pull me to the new drive.
hello, i need help please,
i bought mountain lion,and i have it as file (osxmountainlion.app), i installed it,but can i give it at a friend?
is this file with some way signed with my apple account?,
will i have a problem with my account? thank you
Really? It’s $20—for an entire operating system.
Have your friend look under the couch cushions for change.
that’s not a reply my friend
Yes, it is a reply. I can understand it if you ask the same question when the price of the OS was around $150, but for $20… Just let him buy it.
If he can’t afford an upgrade for $20, how the hell did he manage to buy a Mac in the first place?
Price is irrelevant, stealing is stealing. The OS can be loaded onto multiple computers if they share the same MAS ID (not sure what the seat limit is, it used to be 5 seats in the good old days of DVD installs), which is excellent value for a home set up. But giving a copy to your friend? I doubt that Apple had that in mind, which is why the install is tied to an ID.
Having had problems with upgrading to Lion, I decided to go for a clean install of Mountain Lion, which worked fine.
But when I selectively restored from Time Machine, a lot of things don’t work.
I’m getting error messages for folders saying that I don’t have permission to open them. iTunes is doing the same. Microsoft Office says the applications weren’t installed properly (despite the latest update, which fixed another program).
I don’t know what to try next.
As a guess, do you have the same user id? Possibly if your previous install was done by someone else, this might be an issue?
I don’t have time to explain the details myself right now, but perhaps this might help?
http://www.inteller.net/notes/change-user-id-on-snow-leopard/
Make sure you open Disk Utility, select your hard drive on the left side, and click the “Repair Disk Permissions” button on the bottom. This is suggested ANY time you do an upgrade or even a fresh install/restore from Time Machine.
I am thinking to upgrade to the new osx, but I am affraid, few of the important installed apps will not run in this new osx, anyway, if I upgrade without backup, will it deleted all my apps/files ?
Mountain Lion will neatly separate non-compatible apps into a folder when it installs and tell you the first time you start up.
Personally I have always done a clean install.
As mentioned before, you never know what is left behind and I dislike the thought of “garbage” files on my macs…(bit of a clean freak). Besides, it also gives you the opportunity to scan through all your data to see if/what you really need/use so ML will be efficient and clean.
Time Capsule: I make a back-up of Lion, clean install M Lion and would then erase my Time Capsule and perform a clean back-up too…. (a bit over the top but feels good :) )
Hi everybody,
I own an iMac 21,5 Mid 2011 and even though I see that there is a similar question above, I can’t resist but to make it again. Will I have the permission to redownload all the apps that came with my new Mac if I make a clean install? Did anybody try it with such a machine?
Included apps like AddressBook (now “contacts”), and iCal (now “calendars”), iTunes, etc. will just re-install with the OS. don’t worry about those.
As for iLife (GarageBand, iMovie, iPhoto):
If your Mac is no more than a couple of years old, then when you got it these apps came pre-installed, but in the Mac App Store you would have been prompted to “claim” them (associate your AppleID to the apps). Doing this puts them in your purchase history and you can re-download and re-install anytime. Like, after a clean install of ML.
If your Mac is a bit older (as in pre-Mac App Store) then iLife came pre-installed but your re-installable copies are on the included OS DVD that came with your Mac (in a section I think called “install additional components” or something similar.) If that’s the case, you need to re-install from the DVDs (or pony up the $20 each and just buy them from the App Store for the re-install & update convenience alone).
Make sense?
Oh, and on a mid-2011 iMac, you’re in the “Re-download from the Mac App Store” group.
Check your purchase history before wiping your computer to make sure you see the, in there.
Also, and this should go without saying, we’re only talking about the APPS here, right? So your DATA (your photo library, your iMovie event library, etc) need to be backed up and restored separately.
Good?
Would I be able to do a clean install on a computer that meets ‘Mountain Lion” hardware requirements but is currently running “Leopard”? In other words, could I skip the set of installing “Snow Leopard” from a disc?
Yes, if you do a clean install it does not matter what OS was installed before hand. You can install directly to a new hard drive if you want to.
Well, if you’re using the bootable install drive as outlined above, then sure. Otherwise you need at least Snow Leopard so you have access to the Mac App Store to buy Mountain Lion.
Clean Freak Here….
I have upgraded to Snow Leopard , Lion and soon Mountain Lion.
I always do a fresh install. I am very organised , so for me reinstalling apps and putting data back on doesn’t take much time besides the actual copying. The settings probably takes the most time.
I have never had my mac crash and feel its best to do a clean install as during the life cycle of lion or snow leopard there are many apps i try and find i dont use any more , i remove them via an 3rd party app to get rid of the prefs but still think there could be stuff left over.
A fresh start is as good as a holiday ;)
Agreed Sir!
Manually recreating all the settings on each application and the OS sounds like a night mare. I’ve upgraded from Leopard to Snow Leopard to Lion and now want to go to Mountain Lion. My machine works fine except that I see the swirling beach ball quite often. Two questions:
1. Will a clean install speed up my machine? (I’m assuming there’s a ton of stray data on my Mac now).
2. Any suggestions on how to streamline restoring all the OS and app settings from prior to the install?
Thanks!
The swirling beach ball is EXACTLY the kind of thing a clean install will fix. Computers just need this every once in a while to maintain performance.
It’s not so bad, since a good amount of the preferences and such can be backed up to your iCloud. If you’re worried about any particular non-Apple applications taking a while, you can screenshot (Cmd-shift-3) the preferences page of those apps and stick them with your backups.
Just remember to back up everything you need.
I reformatted my OS/X partition, installed Snow Leopard and then bought and installed Mtn Lion. Works great.
I’m a little disappointed that the dictation is done on an Apple server though.
what are the biggest benefits from doing clean install? I’ve alway just updates the normal way.
If you have issues on your current set up, a clean install will eradicate all problems associated with your user account. If you don’t have any issues, then a normal install will be just fine.
I personally prefer a clean install, you never really truly know what leftovers will be present with any upgrade. However, it takes about 4 times as long to do as plain upgrade.
This was originally an answer to a question that stated:
What do you find as a better choice?
1)
time machine -> backup lion -> clean install mountain lion -> restore from time machine.
2)
time machine -> backup lion -> upgrade to mountain lion.
Is there any workaround to install OS X 10.8 Mountain Lion on an old unsupported mac (MacBook Mid-2007)?
It won’t work. As soon as you try the installer will tell you it can not install on this computer. Even if you could, it would run terribly on an older processors.
Not necessarily – I have a Mac Mini that has the exact same specs as my MacBook – The Mini is technically 1 year newer.
Mac OS Mountain Lion runs beautifully on my Mac Mini but is not supported on my MacBook (Same specs)
Are you sure that the specs really are the same? Same graphics and main chipset, for example? One year is a reasonably long time, and the mini and mobile devices always had some differences.
The ML only supports 64-bit CPU’s. The 2007 MacBook probably still has 32-bit.
hey Gary,
I have the same MacBook Air 13 2011 and I did a clean install 2 weeks ago and yes, I was able to redownload all preinstalled apps that came with the MacBook.
So backup your data and do a safe clean install.
Hope this answers your question!
I’m fairly new to the Mac and I use a Macbook Air I purchased last December. If I do a clean install will I keep the apps that came with that computer? For example, I noticed apps like Garage Band, Face Time and umm I think a couple others.. can be purchased within the App Store, but my Air came with them installed.. I’ve received updates for them in the App Store so I know my account is tied to them, but I just want to make sure if I do a clean install that I won’t have to purchase those apps… Thanks guys!
No, a clean install removes everything: all apps, all files, everything is formatted. If they are stored in your Purchase History through the App Store they could be redownloaded though. If you bought a Mac as recently as December you should probably just do the upgrade through the App Store, it’s very fast on the MacBook Air and much less of a hassle.
FYI, some apps would be retained, since they come with the OS (face time, for example), but iLife (e.g. Garageband) would not.
Sorry for the correction, The apps which u have purchased from Mac App Store which is tied to your apple id will still be available the ‘Purchased’ sections for u to redownload and install again. I’ve tried several times…