If you have a Time Machine backup, you need this support page:
If not, then you'll need to make a Yosemite USB installer of at least 8GB. (a USB3 one will be much quicker).
First download the OS X 10.10 Yosemite installer from the Mac App Store in the Purchases section (you may need to hold alt/option while selecting Purchases. Once it's downloaded, just quit the installer and set the downloaded file's name to InstallOSXYosemite.app (make sure only .app, not .app.app)
- Plug in your USB drive into the computer and open Disk Utility (in Applications).
- Select the USB drive from the left sidebar and click on Erase tab.
- Choose Mac OS Extended (Journaled) in the format box and set the name be YosemiteInstaller
- Now click on Erase button and wait until the format process completes.
- Then choose Partition tab and select 1 Partition from Partition Layout dropdown menu. Click on Option and ensure GUID Partition Table is selected as the partition scheme, with its name set to YosemiteInstaller.
- Launch the Terminal app (in Applications/Utilities) and copy-paste the following command in, and then hit Enter:
- sudo /Applications/InstallOSXYosemite.app/Contents/Resources/createinstallmedia --volume /Volumes/YosemiteInstaller --applicationpath /Applications/InstallOSXYosemite.app --nointeraction
- This will create the bootable USB flash drive. This takes between 10-20 minutes. Do not interrupt the Terminal or eject the flash drive during the process. Once the process completes, you will see the message "Copy Complete. Done."
The OS X Yosemite bootable USB flash drive will be ready for use and you can start the clean installation process.
How to Clean Install OS X Yosemite on Your Mac
- Ensure the bootable USB flash drive is plugged into your Mac and restart the computer. As soon as the start-up chime plays, press the Option key (Alt).
- Choose the USB drive on the start-up drive selection screen and hit Enter/Return on the keyboard.
- Wait until the Yosemite installer appears on screen. This could take a few seconds or minutes.
- Click on Disk Utility and then hit Continue.
- Click on Macintosh HD from the left hand-side pane and then hit Erase tab on the top-right portion of the window. Leave all the settings at their default values and then hit Erase button at the bottom right. This will wipe all files stored on your startup hard drive.
- When the erasing process is complete, return to the first screen where you selected Disk Utility. Now click on Install OS X and then hit Continue.
- Choose the Macintosh HD partition you erased in step 5 and then click Install.
I've followed all steps listed here exactly, but in Terminal when I enter the command it says 'command not found'
Could this be a bug in El Capitan?
Any advice would be great..
No, its not a bug in El Capitan. Just some extra spaces in the command. It should have been
The whole purpose of getting you to rename the downloaded file was to avoid problems with file names which have spaces in them.
Yep, its working now. Thanks so much!
The official instructions on how to fall back are pretty clear. However, I have two problems.
- I did not do a backup immediately before I installed the beta. Yes, by all means berate me, but if I did a backup of my boot disk now using Time Machine would that work? Or doing a backup using some other method? (My key data is on a separate array; what I need are just my Documents and Applications.)
- When I have tried downloading Yosemite to my machine from the App store the system keeps busy for a while but nothing seems to actually download. Any suggestions as to what I might be doing wrong?
As an aside, the beta looks great but at this stage some software I'd really like to use doesn't work and although I can manage without those bits of software I'd really rather not.
Any suggestions as to my two questions above?
hi, i just got a macbook, so i think that's the reason i can't see yosemite in the appstore, because the machine came with yosemite so i have never purchased it from the appstore. if i'm right, where else can i get a copy of 10.10?
Hi, I followed your steps but got sytuck at this point:
"Then choose Partition tab and select 1 Partition from Partition Layout dropdown menu. Click on Option and ensure GUID Partition Table is selected as the partition scheme, with its name set to YosemiteInstaller".
I see no option to "select 1 Parttition" and I got no "GUID Partition Table:. I'm using a 16GB USB, and I have an iMAC.
My resulting box shows:
Partition device "TOSHIBA transmemory Media"
To resize a partition on the selected disk, drag its resize control and press Apply
Device: TOSHIBA TransMemory Media
Scheme: GUID partition Map
Format: OS X Extended (Journaled)
Size: 15..657 GB
So is there no way to revert back to Yosemite while retaining all my original data, without a backup?
I don't like the step the "wipes your startup hard drive" That makes me very nervous!