Unable to create encrypted mount in unprivileged LXD container

[TJ]

On Ubuntu 16.04.3 amd64, with a 17.10 (unprivileged) container, it is not possible to create an ecryptfs mount within the container.

root@sourcecode-u1710:~/overlayfs# mount -t ecryptfs /srv /srv
Exiting. Unable to obtain passwd info

This appears due to ecryptfs-utils as noted in a comment by naisanza in issue #2118 at:

https://github.com/lxc/lxd/issues/2118#issuecomment-236418431

Reported to LXD at https://github.com/lxc/lxd/issues/3990

The error comes from:

src/utils/mount.ecryptfs.c::main()

    pw = getpwuid(getuid());
    if (!pw) {
        fprintf(stderr, "Exiting. Unable to obtain passwd info\n");
        rc = -EIO;
        goto out;
    }