This guide assumes your primary installation disk is already encrypted. If this is not the case, you will have to re-install the OS and when the installer gets to the Disk Setup page, select Advanced Features and choose the Encrypt With LVM option. It asks you for a passphrase and offers to set a backup key on the disk being encrypted, to be moved somewhere else later (if you forget the passphrase). Picking a good passphrase is critical. If you want to get nerdy, the EFF has a take on creating a secure passphrase with
