fscrypt can automatically unlock directories with the user's login password. To do this it ships a PAM module which reads the user's password and loads the respective keys into the user's kernel keyring. Significant inspiration was taken from the ecryptfs implementation.
*** NixOS *** NixOS is a Linux distribution based on the purely functional package management system Nix. More information can be found at https://nixos.org/nixos and in the manual in doc/manual.