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(journaled, encrypted) is a new option which I am able to find in Lion.

Can I convert an existing harddrive (external) to encrypt the whole drive instead of using other tools ?

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Similar question answered in another discussion.… – Slick Aug 16 '11 at 10:12
This question is to do it w/o formatting the disk – Sairam Aug 16 '11 at 11:53
up vote 4 down vote accepted

Whole disks, no, but partitions, yes. While the Disk Utility GUI application cannot, the diskutil command-line utility can do this.

First, come up with a password (such as myVerySecurePassword). I believe this is not tied to your login password, unlike encrypting the boot volume.

Then, find out the identifier for the target volume, e.g. disk1s1:

diskutil list

Then, use diskutil cs convert, like so:

diskutil cs convert disk1s1 -passphrase myVerySecurePassword
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Within Disk Utility you now have encrypted as an option when you erase a partition, but this won't help if you wish to preserve data and convert a drive in use. If you are unhappy with command line tools, you can backup your data, format with encryption via Diam Manager, then restore into it. – stuffe Aug 16 '11 at 9:29
For 99.9% of the population, trying to distinguish 'whole disk' vs 'partition' is pointlessly pedantic and confusing. To take it to the extreme, nothing using off-the-shelf drives is 'whole disk'. – zzz Aug 16 '11 at 11:24
I had originally left that first sentence out. Given the asker's mentioning of encryption, journaling, Disk Utility, etc., I wouldn't classify him as the average user who may not understand the concepts of having multiple volumes on one disk, so I figured I'd mention it. – Sören Kuklau Aug 16 '11 at 19:34
@zzz also note that stackexchange's primary target groups are power users, serious hobbyists and professionals, not the three nines of population :-) @Sören great info! I found out it was impossible to create both encrypted and non-encrypted partitions onto the same disk with Disk, but with diskutil it was possible. NB: just having an encrypted partition on a disk disables the partition tools of the graphical Disk Utility for the disk. – koiyu Sep 6 '11 at 17:10

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