is specified it must be the path of an empty directory
for storing the backup. Otherwise, the backup will be
written to stdout.
+
+Note: currently, if the copy is interrupted a stale lock
+will be left in the LMDB environment. This may be fixed
+in a future release, but until then you must not
+interrupt the copy process.
+
.SH DIAGNOSTICS
Exit status is zero if no errors occur.
Errors result in a non-zero exit status and