eCryptfs is a cryptographic stacked Linux filesystem. eCryptfs
stores cryptographic metadata in the header of each file written,
so that encrypted files can be copied between hosts; the file will be
decrypted with the proper key in the Linux kernel keyring. There is no
need to keep track of any additional information aside from what is
already in the encrypted file itself. You may think of eCryptfs as a
sort of "gnupgfs", or "gnupg as a filesystem".

On Slackware, the Slackbuild script does not install the mount helper
binaries into /sbin, but to /usr/sbin. Because of this, using `mount
-t ecryptfs` won't work, and you must call the `[u]mount.ecryptfs*`
binaries explicitly.

For an unprivileged user to use the `[u]mount.ecryptfs_private`
executables, it is necessary to set the suid bit on them, which the
Slackbuild script also does not do.
