Top tips for downloading and installing OS X Lion
Date: 21st July 2011
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OS X Lion is finally here and it is available for download from the Mac App Store. Although it may be tempting to go straight to the store and click the buy button immediately, there are actually some essential tasks to perform before you should do this. You need to prepare your Mac for the new operating system and check that it is running OK. Any problems with the current OS X installation could cause problems when you upgrade, so here's how to check that it is OK.
You also need to make a backup so that in the unlikely even of a problem during installation, you can turn back the clock and revert to the previous OS X version. You also need to prepare for a 3.5Gb download. There's a right and a wrong way to download Lion. How will you do it?
Check the disk
The first task you need to perform is to check that the hard disk drive is OK. It's not the hardware that you need to check though, it's the filing system. Disk drives run reliably for years, but files can become corrupted quite easily and you don't want to start installing OS X Lion on a system with bad files.
Go to the Applications/Utilities folder and run Disk Utility. Select the hard disk drive on the left and then click Verify Disk. When it has finished, click the Repair Disk Permissions button. Don't be surprised if there are a few errors. All disks have errors and a few aren't usually a problem, but it's best not to let them build up.
Sometimes just doing this once isn't enough to repair all the faults and you might need to repeat the repair functions several times. Files that are in use are not repairable, so you might need to boot up from a USB disk drive containing a backup or from an OS X DVD to run Disk Utility from there.
Get all the updates
Is your current installation of OS X up to date? You will need OS X Snow Leopard of course because it is the only version that has the Mac App Store. You might need to install this on your Mac and then upgrade to Lion. Assuming you have Snow Leopard already running, it is a good idea to use Software Update on the Apple menu to check that you have all the updates that are available. In fact, you won't be able to install Lion if you don't have at least some of the updates, but it is best to get them all.
Back up your Mac
It is essential that you back up your Mac before you install Lion. The chances of anything going wrong are small, but why take a risk?
It is useful to have a Time Machine backup of course, but it is also useful to clone the hard disk drive. You will need a second disk drive, such as a USB drive, and to clone the disk you can use Carbon Copy Cloner or SuperDuper.
Both are free and they make the external drive bootable. Just hold down the Option key a few seconds after switching on the Mac and you'll see all the devices that can be used to start the system - disks, DVDs and so on. In the event of a disaster, you can boot from the USB disk and use CCC or SuperDuper to copy the system back to the internal disk.
Now that your Mac is ready for Lion, you can go to the Mac App Store using the icon in the Dock and buy it. After signing in to the iTunes Store, it will begin downloading. Be aware that this is a 3.5Gb download and it will take many hours or even days if you have a slow internet connection. Don't do it on battery power on your MacBook!
It is best to start it downloading just before you go to bed and then it may have finished by the time you get up the next day. This isn't simply for convenience and ISPs may penalise you if you download too much at peak times of the day. This often takes the form of limiting your bandwidth by up to 75% for a month! This is even if you're on an unlimited bandwidth plan.
Your bandwidth allowence will be greater between midnight and 8am and possibly unlimited - really unlimited. The internet has less traffic during the night and Lion will download faster too.
You might not realise it, but you can pause downloads from the Mac App Store and continue them later. Right click the icon in the Dock and click Pause from the menu that pops up. Right click it again when you want to resume. You can even resume the next day after switching off.
Quit the installer
OS X Lion downloads as an app just like any other. When the download is complete, it then runs automatically. Quit the installer from the menu bar! There are two reasons for this and the first is that you can back up your Mac, which also backs up the OS X Lion installer. You'll then be able to restore the Mac's disk complete with the Lion installer app if you ever need to. The second reason is that the installer contains a disk image which can be written to a DVD-R. This is a dmg file of the Lion installer and it can be used to start the Mac in an emergency.
Open the Applications folder, right click the Lion Installer app and select Show Package Contents. Go to Contents and then Shared Support. You'll see a file called InstallESD.dmg, which is a Lion boot disk. You can use Disk Utility to write this to a DVD-R. You put a DVD-R in the drive, set the source as InstallESD.dmg, the destination as the DVD-writer and then use the Restore function.
After backing up and making your Lion DVD, you can run the Lion Installer app and upgrade.
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