secureErase [freespace] level device
                Erase, using a "secure" (but see the NOTE below) method, either a whole-disk (including all of its par-
                titions if partitioned), or, only the free space (not in use for files) on a currently-mounted volume.
                Secure erasing makes it harder to recover data using "file recovery" software.

                Erasing a whole-disk will leave it useless until it is partitioned again.  Erasing freespace on a vol-
                ume will leave your files intact, indeed, from an end-user perspective, it will appear unchanged, with
                the exception that it will have attempted to make it impossible to recover deleted files.

                If you need to erase all contents of a partition but not its hosting whole-disk, use the zeroDisk or
                randomDisk verbs.  Ownership of the affected disk is required.

                Level should be one of the following:

                      o   0 - Single-pass zero-fill erase.

                      o   1 - Single-pass random-fill erase.

                      o   2 - US DoD 7-pass secure erase.

                      o   3 - Gutmann algorithm 35-pass secure erase.

                      o   4 - US DoE algorithm 3-pass secure erase.

                NOTE: This kind of secure erase is no longer considered safe because modern devices have wear-leveling,
                block-sparing, and possibly-persistent cache hardware. The modern solution for quickly and securely
                erasing your data is strong encryption, with which mere destruction of the key more or less instantly
                renders your data irretrievable in practical terms.