В утилите rm есть возможность удалять «намертво» на FreeBSD:
man rm
rm -P Overwrite regular files before deleting them. Files are over-
written three times, first with the byte pattern 0xff, then 0x00,
and then 0xff again, before they are deleted. Files with multi-
ple links will not be overwritten nor deleted unless -f is speci-
fied, a warning is generated instead.
Specifying this flag for a read only file will cause rm to gener-
ate an error message and exit. The file will not be removed or
overwritten.
Но только все зависит от того, что снизу