Are you paranoid? I am.
If you keep most of your work on a net-book/laptop, you should consider the possibility of having it lost or stolen. All the backups in the world will not prevent someone else from having full access to all your personal and embarrassing information. One way to get around this is to encrypt your hard drive. The safest way is to encrypt the whole drive before the operating system is installed. Encrypted installation is offered by Debian, and soon by SUSE.
To be really safe, you should keep check-sums of your unencrypted boot sectors, etc, on your encrypted partition, to prevent tempering with the few unencrypted bits. But, if you didn’t piss the KGB off very recently, you might feel safe with encrypting only the folder that contains your user documents. Under Windows Vista +, that would be \Users\YOUR USER NAME, but I suspect that would inevitably leave some loose ends. One way or another, if your are even slightly paranoid, you are probably not using Windows. On Linux, encrypting your home directory is probably reasonable enough.
Here are 10 steps to accomplish this on Debian/Ubuntu systems (Adapt to your Linux/BSD/OpenSolaris):
1. Install the packages: initramfs-tools, hashalot and lvm2:
$ sudo apt-get install initramfs-tools hashalot lvm2
2. load (or make sure have been built into the kernel) the modules: aes-x86_64 or aes-i586, dm-crypt and dm-mod:
$ sudo modprobe aes-x86_64 dm-crypt dm-mod
3. Create (or designate) a partition that would be encrypted. Allow enough room because I’m not sure growing it later is an option. Any data on it will be destroyed:
$ sudo fdisk /dev/YOUR DRIVE ON WHICH THE TO-BE-ENCRYPTED PARTITION IS
4. Check for bad blocks:
$ sudo /sbin/badblocks -c 10240 -s -w -t random -v /dev/YOUR TO-BE-ENCRYPTED PARTITION
5. Fill you to-be-encrypted partition with random data. Note: (This takes AGES, but makes things safe. By ages I mean ~ 2 hours for every 10 GB):
$ sudo dd if=/dev/urandom of=/dev/YOUR TO-BE-ENCRYPTED PARTITION
6. Setup an encrypted luks volume
$ sudo cryptsetup -y –cipher aes-cbc-essiv:sha256 –key-size 256 luksFormat /dev/YOUR TO-BE-ENCRYPTED PARTITION
7. Unlock it:
$ sudo cryptsetup luksOpen /dev/YOUR TO-BE-ENCRYPTED PARTITION pvcrypt
8. Create a volume group and a volume:
$ sudo pvcreate /dev/mapper/pvcrypt
$ sudo vgcreate vg /dev/mapper/pvcrypt
$ sudo lvcreate -n VOLUME-NAME -L VOLUME-SIZE vg
9. Create a file-system on /dev/mapper/vg-VOLUME-NAME:
$ sudo mkfs.ext3 /dev/mapper/vg-VOLUME-NAME
10. Edit /etc/fstab. Add the line:
mount -t ext3 /dev/mapper/vg-VOLUME-NAME /home
9. Edit /etc/crypttab. Add the line:
pvcrypt /dev/YOUR-ENCRYPTED-PARTITION none luks,retry=1,lvm=vg
10. This is the fun part: log out all users, switch to a console and login as root. Move the /home directory to be /home-SOMETHING. Create a new empty /home directory, and mount the encrypted volume in it. Then copy the entire contents of your /home-SOMETHING into /home preserving all attributes, times and ownerships. Here’s a few simple steps to do it:
$ sudo mv /home /home-plain
$ sudo mkdir /home
$ sudo mount /dev/mapper/vg-VOLUME-NAME /home
$ sudo cp -aR –preserve=all /home-plain/* /home/
Ready to see if it worked? Reboot! you should do this from the console directly:
$ sudo /sbin/reboot
Upon boot up, when your system tries to mount your /home partition, which is now encrypted, you will be asked for a password before booting continues. After the correct password is supplied, the system boots on.
If you have more locations you would like to encrypt, you can create more volumes on the encrypted volume group. To understand how to, or for a detailed guide for installing Ubuntu Linux on an encrypted volume group to begin with, see the page from which I’ve adapted the steps above.