Although TrueCrypt looks like free software, concerns over its licence prevent its inclusion in Debian. Truecrypt is also developed in a closed fashion, so while the source code is freely available, it may receive less review than might a comparable openly developed project.
For the above reasons, Tails developers do not recommend TrueCrypt. We include TrueCrypt only to allow users of the (old and now unsupported) Incognito live system to access the data on previously created media.
In the future, we would like to replace TrueCrypt with a compatible alternative. However, there might be some time during which that is not possible, and moving away from TrueCrypt is the only sensible way we can go. This means that you should not create new TrueCrypt media if you intend to stay with Tails in the long run.
Using TrueCrypt in Tails
TrueCrypt is not enabled by default when Tails starts. In order to use TrueCrypt, add the truecrypt boot option to the boot menu. For detailed instructions, see the documentation on using the boot menu.
Once Tails has started, to start TrueCrypt choose .