What you should do before installing OS X Yosemite

OS XApple has posted a beta copy of its next version of OS X for the Mac, called Yosemite, on the web for all to download. You can grab a copy of this for free, install it on your Mac and get a next-generation operating system right now. It sounds fantastic, but installing it is not quite as straightforward as you might think and there are some essential tasks to perform before you start.

If you want to know what is in the brand new, as yet unfinished, OS Yosemite, there is plenty of information on the Apple website. For those that cannot wait for the finished version and want to download the Yosemite beta, they can do so from here.

Yosemite Beta

Run Disk Utility

The first task to perform when getting ready to install Yosemite is to check that the Mac's disk is in good health. You don't want to make major changes to the system if there are damaged or corrupt files because it could result in disaster.

Go to the Applications, Utilities folder and run Disk Utility. Select the Mac's disk drive on the left and there are two buttons to use: Verify Disk and Verify Disk Permissions. The results of using these are show in the window, so if there are any problems, use the buttons below: Repair Disk Permissions and Repair Disk.

Disk Utility in OS X on the Apple Mac

Verify Disk is always fine, but I have never been able to totally eliminate every single disk permission error. It hasn't caused any problems, so don't worry if you cannot fix everything. Just run the repair tools a couple of times and every thing that can be repaired, will be repaired.

Run SuperDuper!

The next step is to back up the Mac's disk drive. There are several ways to do this, but my current favourite is SuperDuper!. This is a free utility that can be used to clone the Mac's internal disk drive to an external USB drive. After copying the drive, you can even boot up from it and it's identical in every way to the Mac's disk. Hold down the Option key just after switching on the Mac to choose which disk to boot from.

SuperDuper backup for OS X

Time Machine backups are also useful and I use a large external USB drive with two partitions, one for a SuperDuper! clone of the Mac's disk and one for Time Machine to use. The disk you back up to doesn't have to be the same size as the Mac's, it just has to be big enough to fit all your files on. That's why I'm backing up 400GB to a 250GB disk - there are less than 250GB of files.

Now you are ready to download and install OS X Yosemite. You can actually download Yosemite first, but quit the installer when it runs so that you can run Disk Utility and SuperDuper!. This has the added advantage of backing up your OS X Beta download too. You can run the Install OS X Yosemite beta.app from the Applications folder just by clicking it.

If it all goes horribly wrong, which is actually very unlikely, you simply boot up from the external clone drive and use SuperDuper! to clone everything back to the Mac's internal drive and you are back where you started with no harm done.





Installation issues with Yosemite are as likely as snow in winter! Simply google "yosemite verify and repair" to see what I mean.

When a large number of people use software, a very small failure rate can result in a lot of angry people. I don't know how many have installed Yosemite so far, but it is likely to be a lot. If just 1% of people have problems, that would mean thousands of people. It can seem like there are lots of problems when actually 99% of people have none. So I think it is true to say that most people won't have problems. You are more likely to be in the 99% that don't have a problem than the 1% that do. I'm only using these percentages to illustrate a point, I don't know what the actual figures are, but I'd guess that problems are rarer than people imagine.

Ever since going thru all of these steps to install Yosemite, SuperDuper itself fails to write to any external disk or disk partition. I go through all of the standard disk utility routines, verify repeatedly that the target disk is OK, and still no love. It takes more than an hour for SuperDuper to fail. Shirt pocket says the external disks are the problem. Whatever. Apple and ShirtPocket, please get your shirt together and fix this basic, essential problem. Thanks.

I regularly use SuperDuper with an external USB drive and have not had any problems, so I don't know how common this fault is.

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