TODO
----
+Concurrent disk writes may fail on captive_file_write() .Information==num_bytes
+
Strict ulimit (rlimit) of sandbox child.
Set direct-write buffers limit for sandbox child.
-'captive' account as pre/post-install.
syslog(3) GLog reporting.
Better BLKGETSIZE64 vs. BLKGETSIZE run-time availability compatibility.