If you have multiple computers that need the El Capitan upgrade, then a bootable install flash drive will make the process easier and faster, since the install file is over 6 GB in size (about a gig larger than Yosemite was!) and could take some time to download on each computer individually.
If you’re going to use El Capitan on your only computer, it’s wise to install it as a dual-boot system, that way you can easily switch back to Yosemite whenever things get buggy.
When the developer edition of Yosemite came out, the process for creating a bootable install drive was fairly complex and prone to errors. This time, I’m going to skip that long, complicated process in favor of using DiskMaker X. Even though it has not been updated to work with El Capitan yet, it still works—you just have to trick it into thinking it’s creating a Yosemite drive.
Step 1: Download the OS X 10.11 Beta
Once you’ve downloaded the Developer Beta or the Public Beta from the Mac App Store, don’t install it just yet—it will auto-erase the installation app you need. Close out of the installation screen that pops up, then hunt for “Install OS X 10.11 Developer Beta” or “Install OS X El Capitan Public Beta” in your Applications folder to verify it’s there.
Step 2: Install DiskMaker X
If you don’t already have DiskMaker X installed, go ahead and do that now from the DiskMaker X website. The newest version should be DiskMaker X 4.0b4.
Step 3: Rename the El Capitan Installer
Just in case something went wrong, I chose to copy the “Install OS X 10.11 Developer Beta” (or “Install OS X El Capitan Public Beta”) to my Downloads folders so I wouldn’t have to re-download the installer again should a problem arise. You don’t have to.
Change the name of the “Install OS X 10.11 Developer Beta” (or “Install OS X El Capitan Public Beta”) file to “Install OS X Yosemite” instead. This just needs to be done in order to trick DiskMaker X into creating a bootable install drive for it. If you don’t rename it, DiskMaker X will throw you an error.
Note: Delete Any Old Installers You May Have
If you still have an installer for Yosemite on your hard drive, make sure to delete it before proceeding. DiskMaker X might try and use that file instead of the El Capitan one, which means you will have to start all over.
Step 4: Choose to Make a Yosemite Drive
Open up DiskMaker X and select “Yosemite (10.10)” from the window.
Step 5: Choose Your Fake “Yosemite” File
DiskMaker X should automatically find the file that’s either in your Applications or Downloads folder. Go ahead and choose “Use this copy.”
Step 6: Get Your USB Flash Drive Ready (Optional)
Before proceeding, make sure you have copied all of your important files from your USB flash drive to another place, because this process will wipe your flash drive and reformat it. Also, make sure that your flash drive is 8 GB or more, because the installer file alone is over 6 GB.
Update: While you need at least 8 GB free to install El Capitan, it might not be enough to make a bootable drive. So if you get an error saying there isn’t enough disk space, you’ll need to get a 16 GB or larger thumb drive.
Step 7: Select to Use a Thumb Drive
No matter what size thumb drive you’re using for this, select “An 8 GB USB thumb drive” from the next window. Again, an 8 GB stick might not actually be big enough, so you’ll probably need a 16 GB or larger stick.
Step 8: Choose Your Thumb Drive
Make sure to select the right one. I renamed mine EL CAPITAN so I wouldn’t confuse it with any other drives.
Step 9: Erase & Create the New Disk
At the warning, select “Erase then create the disk.”
The hit “Continue.”
In a minute or so, it’ll ask you for your admin password. Input it, then be prepared to wait awhile, depending on the speed of your USB drive.
Mine took about 45 minutes, and Activity Monitor even said DiskMaker X was “not responding.” However, it was doing its work—just be patient. As you can see, I finally got a message saying my boot disk was ready, and it’s called “Yosemite Install Disk – 10.11.”
Step 10: Install El Capitan on Your Computer
To install El Capitan, make sure the USB drive is inserted into the computer, then restart the computer while holding the Option (alt) key on your keyboard. Wait until the Startup Manager pops up, then select the “OS X Base System” volume. Alternatively, you can just hold down the C key while starting up to boot directly into the USB drive.
Then just follow the install instructions and wait for your new El Capitan experience. When you come to the Install OS X screen, make sure to select the right disk. I created a new partition on my hard drive called “El Capitan,” so I used that.
Once it’s done installing, you’ll get to the Welcome screen, and you should be able to figure it out from there.