unwrap an eCryptfs wrapped passphrase, rewrap it with a new passphrase, and write it back to file.
printf "%s\n%s" "old wrapping passphrase" "new wrapping passphrase" | ecryptfs-rewrap-passphrase [file] -
ecryptfs-rewrap-passphrase is a utility to change the wrapping passphrase on a wrapped passphrase file.
This manpage was written by Dustin Kirkland <firstname.lastname@example.org> for Ubuntu systems (but may be used by others). Permission is granted to copy, distribute and/or modify this document under the terms of the GNU General Public License, Version 2 or any later version published by the Free Software Foundation.
On Debian and Ubuntu systems, the complete text of the GNU General Public License can be found in /usr/share/common-licenses/GPL.