With Yosemite (OS X 10.10) and the OS X Beta Program, Apple is for the first time since 2000 making pre-release versions of a new operating system available to people other than developers. Specifically, the first million non-developers to sign up for the 10.10 public beta will get to download and install pre-release versions of Yosemite, with the goal being to help Apple find and fix bugs before the OS is officially released.
Should you sign up? Keep in mind that these are pre-release versions of Yosemite, so they'll have bugs, and some features and services won't work as expected. As we explained in our FAQ, unless you really need to test particular software on pre-release versions of Yosemite; have an extra Mac or drive you can dedicate to testing; have a good backup plan; and have the time and patience to deal with--and, just as important, report--any bugs you come across, you should probably take a pass and just wait for Yosemite to be released later this year.
Macworld also has bootable-install-drive instructions for Mavericks (OS X 10.9), Mountain Lion (OS X 10.8), and Lion (OS X 10.7).
If you do decide to participate in the Yosemite beta program, I recommend creating a bootable installer drive, on an external hard drive or a thumb drive (USB stick), for many of the same reasons I recommend making a bootable Mavericks installer drive: If you want to install the Yosemite beta on multiple Macs, using a bootable installer drive can be more convenient than downloading or copying the entire installer to each computer. If you need to erase the drive on your test Mac before installing Yosemite, or start over at any time, you can use a dedicated installer drive to boot that Mac, erase its drive, and then install the OS. And if your beta-testing Mac is experiencing problems, a bootable installer drive makes a handy emergency disk.
As with previous versions of OS X, it's not difficult to create a bootable installer drive from the Yosemite beta installer, though the processes have changed slightly since Mavericks. I show you how, below.
[Editor's note: With every major new version of OS X, we publish a comprehensive guide to installing the OS. We'll do that for Yosemite when it's officially released, so stay tuned. We'll also be updating this article with any changes that arise in subsequent Yosemite betas, as well as in the final release.]
Keep the installer from being deleted
Like all recent versions of OS X, the Yosemite beta is distributed through the Mac App Store. Specifically, if you're accepted into the Yosemite beta program and log into the OS X Beta Program site, you're provided with a redemption code for the Mac App Store. You use that code in the Store to download the Yosemite beta installer.
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