Creating a new directory for an SMB client is a very complex task! It includes things like inheriting permissions from the parent directory and storing DOS attributes. Other clients should not see the existence of the directory that is in progress of being created! This option is an enumerated type that controls the usage of a temporary directory name. When this is set to yes, the directory name will be prefixed with '.::TMPNAME:D:$SERVERID:' (where $SERVERID is a unique identifier for the current process). When this option is set to Auto (the default), the server uses a temporary directory name if, at least, one of the following options is effectively not set to no: , , , or . Note on OpenBSD Auto (the default) is mapped to no, see https://bugzilla.samba.org/show_bug.cgi?id=15801. A re-export of an SMB/CIFS mount might one rare case where vfs mkdir use tmp name = no could be useful. In most cases vfs mkdir use tmp name = Auto should be kept. Auto