It's not possible. TrueCrypt only supports system encryption of Windows operating systems. See here: http://www.truecrypt.org/docs/sys-encryption-supported-os#Y0 The way to do it on Linux is with LUKS/dm-crypt, but it's more complicated than encrypting the volume. The boot partition has to be unencrypted in order to boot the kernel to decrypt the rest of the disk / volume, and currently the boot folder is part of the unwritable Tails system image. The Tails developers would have to modify the default Tails configuration to support it. Here's a discussion about it: https://tails.boum.org/forum/Persistent_Truecrypt_+_encrypt_entire_system_drive/