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One of the most versatile and powerful tools included with Lion is Disk Utility. You can use it to create and partition hard drives, as well as diagnose a funky drive and repair its disk permissions. You'll find Disk Utility in the Utilities folder and we can get there from the Go menu. so Go > Utilities. Here's Disk Utility and we'll launch it. Along the left side, you will see any hard drives and volumes that are attached to your Mac. Those volumes that are grayed out are unmounted. Now, if I were to mount a volume, I simply select it and I click the Mount button here at the top of the window and here's my mounted volume.
Normally, when people launch Disk Utility, they do so to use First Aid and you use this for a couple of reasons. one is that you want to repair disk permissions and what does that mean? The Mac OS is based on UNIX, which has a system whereby specific user accounts have a variety of powers or permissions they could use on that Mac. So for example, the root user can do anything, whereas a standard user's capabilities are much more limited. Now sometimes these permissions can get scrambled which can lead to situations where you can't move or open a file, because the Mac thinks that you have the wrong permissions for example.
To check permissions, you just select a volume and you can either verify permissions or you can repair permissions. Now, quite honestly, you can click Verify Permissions, but if you find a permission that's out of whack, you are going to want to repair it anyway, so I just simply click on Repair Disk Permissions and we'll do that now. This can take a few minutes. And lucky me! I just had one warning and it wasn't really something that needed to be repaired, and that is often the case.
Sometimes, you will see a message time, and time again no matter how many times repair permissions. Don't worry about it. They are not really a problem. You also have the option to verify and repair a disk. When your start-up disk is selected, you don't have the option to repair it. You can only verify it, because you're not allowed to repair a disk that you boot from. However, if you select a different volume, for example I will select this external hard drive, I have the option to then repair the disk as well. Verifying this drive will take a while, so I won't do it now.
Another option you have is to erase the drive. So I will select the drive, I will click on Erase, and you see that I have the option to format the drive in a variety of format. The one you want to use is Mac OS Extended (Journaled) and that's the one that's selected by default. Here you can also name your drive if you want to and then click on Erase. When you click on Erase, you will be asked to confirm that you really want to do this, because this will wipe all the data off the drive. So you don't want to do this lightly. One other thing to note here is the Security Options button.
Click this and you'll see that you have the option to erase the drive in many different ways. You can use Fastest which simply deletes the data directory. It doesn't remove the data from your drive but it allows your Mac to overwrite the data that's currently on your hard drive with new data. If you adjust this slider, you can then choose to overwrite the data that's currently on your drive with nonsense. So the first notch is to overwrite it one time, the second notch is to overwrite it three times, and the last notch is to overwrite it seven times. This is excessive.
It takes a really long time to overwrite data seven times. Even three times as quite a bit. If you want to be really secure, feel free to choose one of these higher options and let this happen overnight. By the time, you get up in the morning, your drive will be overwritten. For most cases, you can simply leave it to Fastest, click OK and you're good. I want to keep the data that's on my drive now, so I'm not going to erase it. Now let's look at Partition. Click the Partition tab and you see you have the option to divide your drive into multiple volumes.
Currently, this volume is divided into two partitions, but I can choose a different partitioning scheme. I can have it divided into 10 partitions if I like, and each one of these is treated as a separate volume and would appear on my desktop as such. While we're looking at partitions, let's look at Options. Click the Options button. Here you're going to see a sheet with three different options. In most cases you want to make sure the GUID Partition Table is selected. This is the formatting option you'll use to create a recovery drive, as I will discuss later when talking about preventive troubleshooting measures.
For now, we'll cancel. And when you're ready to partition your drive, simply click on Apply. Again, I don't want to partition this drive, so I'll go back to First Aid, and I will switch without partitioning the drive. Now, one last thing before we leave Disk Utility. Using this application, you can create virtual volumes called disk images. To do this, you choose File > New and then Blank Disk Image. In the window that appears, you can name your disk image. You can choose its size.
We will leave it at 100 MB for now. You can also choose its encryption. In this case, I am going to choose 128 bit AES encryption. Save it to the desktop and I will click Create. Because I chose to use encryption on this disk image, I have to supply a password. I am choosing a weak password. Please don't follow my lead. Make sure that you uncheck Remember password in my keychain, and click OK.
So here's my mounted disk image. I open it and it looks just like another volume. I will open TextEdit, I will save that, put it on the desktop, and I will quit TextEdit. Now, I will take my file and drag it into my disk image. Close the window and I will eject the disk image. So where is it? It's right here within this disk image.
To find my file, I double-click on it and I'm prompted for my password. Click OK. Here's the disk image, and here's the file that I have saved in it. So what's so good in this? This is one way to create a protected archive, so that nobody but you can open it. So if you have documents that you want to keep from prying eyes, this is one way to do it. So I'll eject my image, toss out these files, close Disk Utility, and there you are.
Disk Utility's greatest talents.
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