Encrypting partitions with cryptsetup

Encrypting Existing Partitions

Cryptsetup has more – many more – options, but these should be enough to show you how to start using encrypted partitions, especially if you only want a vault.

Encrypting an existing directory, such as /home, is more complicated but is as much a matter of organization as of learning more commands. To encrypt an existing partition, follow these steps:

1. Copy all the files to another partition. As described above, you might want to create a partition of at least equal size.

2. Set up and map the encrypted partition. For convenience, use its existing directory name, such as /home.

3. Create a passkey file in the /root directory so that the device automounts at boot with:

touch /root/[MAPPED DEVICE]_passkey && chmod 600 /root/[MAPPED DEVICE]_passkey

4. Map the device with:

cryptsetup luksAddKey /dev/[DEVICE] /root/freeagent_passkey

5. Create a filesystem on the encrypted device.

6. Add the following line to /etc/fstab:

/dev/mapper/[MAPPED-NAME] [MOUNT POINT]] ext4_netdev 1 1

7. Add the following entry to /etc/crypttab:

[MAPPED NAME]/dv/ [DEVICE]/[MOUNT POINT]

8. In the case of /home, copy the hidden files to the encrypted partition, then test by rebooting. If no problems appear, copy the rest of the files to the encrypted version of /home/.

Encryption, as you can see, is more complicated than checking a box when you tackle it hands-on. However, the amount of control that do-it-yourself encryption can bring will make it worth the effort, because you are getting exactly what you want.

Bruce Byfield

Bruce Byfield is a computer journalist and a freelance writer and editor specializing in free and open source software. In addition to his writing projects, he also teaches live and e-learning courses. In his spare time, Bruce writes about Northwest coast art. You can read more of his work at http://brucebyfield.wordpress.com

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