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HenryL

So what's a DMG file

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WHAT IS A DMG?

 

 

Is it like a 'virtual cd'

 

When you double click it, it 'mounts' like a real cd (or disc) would. You can eject it and it then 'disappears'

 

 

Is my understanding correct? Is the above true?

 

 

 

What about password protecting disk images?

 

I have an external firewire 250GB drive. It had loads of media and video files on it. I would like it so that only I can decrypt it. For example I might have the entire south park back catalogue

 

 

What do I need to keep in mind? Do I need a certain amount of free space on my hard drive (for it to 'unzip' or decrypt' to?)

 

Also, does it decrypt and creat the 'temporary' cache file on the laptop hard drive or the external hard drive? (So - for security reasons - could someone 'undelete' the file if they DIDN"T have the external firewire drive?)

 

 

 

 

Hope the above makes sense, happy to explain again.

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WHAT IS A DMG?

Is it like a 'virtual cd'

 

When you double click it, it 'mounts' like a real cd (or disc) would. You can eject it and it then 'disappears'

Is my understanding correct? Is the above true?

What about password protecting disk images?

 

I have an external firewire 250GB drive. It had loads of media and video files on it. I would like it so that only I can decrypt it. For example I might have the entire south park back catalogue

What do I need to keep in mind? Do I need a certain amount of free space on my hard drive (for it to 'unzip' or decrypt' to?)

 

Also, does it decrypt and creat the 'temporary' cache file on the laptop hard drive or the external hard drive? (So - for security reasons - could someone 'undelete' the file if they DIDN"T have the external firewire drive?)

Hope the above makes sense, happy to explain again.

 

 

Just found this website: http://www.wikihow.com/Make-a-DMG-File-on-a-Mac

 

How to Make a DMG File on a Mac

 

The easiest way to store files for a Mac is to create a Disk Image. A Disk Image is a file which has the properties of a separate hard drive or CD. It has a set size limit and options for encryption to keep your files safe and secure.

Steps

 

1. Start up your Mac.

2. Create a New Folder and place the files you would like in your disk image into this new folder.

3. Right click (or CTRL-Click) the folder and select "Get Info" and note the size of it's contents.

4. Open Disk Utility (Applications > Utilities > Disk Utility)

5. Click the "New Image" icon to create a new disk image. Enter a name for the Image, and select a size adequate for the size of your folder you created in Step 2. Set the encryption to "none" and Format to "read/write disk image". See Tips to learn how to encrypt the image.

6. Place the contents of the folder from Step 2 into the newly mounted disk image

7. Unmount the Disk Image

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Just found this website: http://www.wikihow.com/Make-a-DMG-File-on-a-Mac

 

How to Make a DMG File on a Mac

 

The easiest way to store files for a Mac is to create a Disk Image. A Disk Image is a file which has the properties of a separate hard drive or CD. It has a set size limit and options for encryption to keep your files safe and secure.

Steps

 

1. Start up your Mac.

2. Create a New Folder and place the files you would like in your disk image into this new folder.

3. Right click (or CTRL-Click) the folder and select "Get Info" and note the size of it's contents.

4. Open Disk Utility (Applications > Utilities > Disk Utility)

5. Click the "New Image" icon to create a new disk image. Enter a name for the Image, and select a size adequate for the size of your folder you created in Step 2. Set the encryption to "none" and Format to "read/write disk image". See Tips to learn how to encrypt the image.

6. Place the contents of the folder from Step 2 into the newly mounted disk image

7. Unmount the Disk Image

What about elastic disk images that will dynamically change size based on what you have in them. How do you make those?

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What about elastic disk images that will dynamically change size based on what you have in them. How do you make those?

 

I believe you follow the same procedure, but when you create your file, select 'sparse image' from the drop down list

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I believe you follow the same procedure, but when you create your file, select 'sparse image' from the drop down list

no good. It does let you select sparse image but you also have to choose a file size. I tried a 40mb sparse image dmg file then tried putting a larger file into it but really was only 40mb large.

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Create a sparse image that's big enough to cover the entire external drive. That's how large it MAY become. As you'll notice, it'll start off being tiny!

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While xerent is completely correct, I would have to warn against Sparse DMG's for certian uses. While it may seem like a great option (and often is), it can also prevent you from performing certain actions. This is especially true of backup. When you backup using SuperDuper! and many other applications they will allow you to backup, but not completely restore from a Sparse image. You can also migrate from a RO-DMG, but not from a Sparse.

 

Food for thought; think before you act.

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