I asked this question on the ecryptfs launchpad, but it expired there without answer. https://answers.launchpad.net/ubuntu/+source/ecryptfs-utils/+question/235226
It might be trivial, but I really don't want to get it wrong for obvious reasons. On the other hand, the answers that I find are all related to the Ubuntu home directory encryption where a wrapped passphrase is used and they're confusing me.
Question: I am mounting a directory as ecryptfs
sudo mount -t ecryptfs -o ecryptfs_cipher=aes,ecryptfs_key_bytes=16,ecryptfs_passthrough=no,ecryptfs_enable_filename_crypto=yes /srv_backend /srv_use
Now I want to backup the encrypted folder /srv_backend. What do I need to backup apart from the obvious data there and my password.
The command line reply mentions a "Filename Encryption Key (FNEK) Signature [3c2034c2f35aab36]". What is this used for? Do I need to back it up / remember it?