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Annotation of 43BSDReno/share/doc/ucs/mmdf/p3, revision 1.1

1.1     ! root        1: .SH
        !             2: The MMDF File Hierarchy
        !             3: .PP
        !             4: The MMDFI queue structure consisted of three directories.
        !             5: The ``msg'' directory contained the files containing actual
        !             6: message text.
        !             7: The ``addr'' directory contained the address list file for each
        !             8: message, and the ``tmp'' directory contained the address list
        !             9: while it was being created before moving it to the ``addr''
        !            10: directory.
        !            11: The names of the files in ``msg'' and ``addr'' were identical
        !            12: although the contents differed.
        !            13: This made it easy to find
        !            14: the companion file given either filename.
        !            15: The MMDFII queue structure has changed in one major way from that
        !            16: of MMDFI.
        !            17: There is now one extra directory per channel named q.\fIchannel\fR.
        !            18: If an address list still has any addresses destined to be sent
        !            19: on any channels,
        !            20: then a link will exist from the address list
        !            21: file in ``addr'' to a file with the same name in each queue directory
        !            22: which is referenced.
        !            23: All the above directories usually live in /usr/mmdf/lock/home,
        !            24: although the
        !            25: root name of this tree can be changed.
        !            26: The lock directory is kept in 700 or 770 mode, accessible only to
        !            27: the ``mmdf'' user and possibly a ``systems'' group for
        !            28: ease of maintenance.
        !            29: The ``home'' directory and all the underlying queue directories are
        !            30: kept in 777 mode to allow ease of movement and access for the trusted
        !            31: but unprivileged programs that operate there.
        !            32: In particular, the \fBsubmit\fR process is setuid to ``mmdf''
        !            33: to allow it to
        !            34: enter the tree, but it then restores
        !            35: its UID and GID to those of the invoker.
        !            36: \fBDeliver\fR and the channel programs normally run as the ``mmdf'' user.
        !            37: Only the local channel, which must access the real user's mailbox files,
        !            38: and the TCP/IP network daemons, which must access privileged sockets,
        !            39: need run privileged.  There are several other programs that are
        !            40: setuid to ``root'', but only so they can change their UID to ``mmdf''
        !            41: so as to to be a ``trusted submitter'', which allows them to specify
        !            42: an arbitrary From: line.
        !            43: .PP
        !            44: The addition of the separate queuing directories on
        !            45: a per channel basis was a valuable change.
        !            46: UNIX performs poorly with large directories,
        !            47: as any UUCP backbone site can tell you.
        !            48: This new mechanism allows easy
        !            49: partitioning of channel activities into separate directories, since
        !            50: \fBdeliver\fR will never access the copy of the address list in the ``addr''
        !            51: directory until it goes to finally expunge the message from the queues.
        !            52: If one channel or site gets backed up, it does not affect the performance of
        !            53: any of the other channels.
        !            54: .PP
        !            55: The format of the address lists has changed somewhat since MMDFI.
        !            56: The old format was:
        !            57: .in +1i
        !            58: .sp .6
        !            59: S T channel-name host-on-channel address-at-host
        !            60: .in -1i
        !            61: .sp .6
        !            62: where S was either a `\-' indicating unsent or a `+' indicating that
        !            63: only the address but not the text had been sent.
        !            64: The T was either the type of delivery
        !            65: (almost always `m' for mail) or a `*' indicating the message has been
        !            66: completely delivered.  The channel-name and host-on-channel should be
        !            67: obvious.  The address-at-host parameter was only the local part of an
        !            68: address.
        !            69: The new version differs in two ways.  First, the host-on-channel is now
        !            70: the full domain address of the host to deliver to, as specified in the
        !            71: routing information of the domain table.
        !            72: .FN
        !            73: See the manual section on the MMDF database (queue.5) for more information.
        !            74: .FE
        !            75: Second, the address-at-host is now the full address with
        !            76: both the local-part and the domain specifier.
        !            77: .PP
        !            78: In the future, I will probably change the location of the ``message
        !            79: completely delivered'' flag to be in the first position (S), since
        !            80: I feel it was a mistake to not have it there in the past and it is
        !            81: confusing in its current position.
        !            82: This has not been done as of February 1985.
        !            83: .PP
        !            84: The MMDF file hierarchy also has a logging directory.  Separate
        !            85: logs are kept here for \fBsubmit\fR and \fBdeliver\fR,
        !            86: the channel programs,
        !            87: and the phone dialing package.  This directory is generally
        !            88: accessible although unreadable and the logs are normally write
        !            89: only.  This could be made ``mmdf'' access only for some sites, with
        !            90: the only penalty being that some programs would be unable to add
        !            91: entries to the log.
        !            92: A subdirectory of the log directory called ``log/phase'' contains
        !            93: time stamp files whose modification times are changed by \fBsubmit\fR
        !            94: and \fBdeliver\fR to indicate such things as last pickup time, last
        !            95: delivery time, last poll made, and similar information.
        !            96: .PP
        !            97: There are two other directories in the MMDF hierarchy which
        !            98: should be mentioned.  The ``chans'' directory contains
        !            99: all of the channel programs invoked by the \fBdeliver\fR program,
        !           100: and other ancillary daemon programs such as the SMTP daemon
        !           101: and the SMTP server.  The ``table'' directory contains
        !           102: all files necessary to maintain the MMDF database,
        !           103: including domain tables, host address files, mailbox
        !           104: alias files, dialing scripts, and programs to build these
        !           105: files and incorporate them into the DBM library.
        !           106: .FN
        !           107: The DBM package is a set of simple hashed database access routines
        !           108: that were distributed with V7 Unix and are still widely used.
        !           109: .FE
        !           110: .PP
        !           111: Use of some sort of keyed database system is almost essential for large
        !           112: MMDF systems, since the table lookup overhead is unbearable
        !           113: otherwise.  Currently DBM is the only readily available alternative
        !           114: and it does seem to work well, but it is running out of steam,
        !           115: particularly due to its limited record length.  A more
        !           116: flexible replacement for
        !           117: this package would be welcome.
        !           118: .PP
        !           119: The top of the MMDF directory tree contains the directories mentioned
        !           120: above, the \fBsubmit\fR and \fBdeliver\fR
        !           121: programs, and a few maintenance programs.
        !           122: If the site is polled for PhoneNet mail then the ``\fBslave\fR''
        !           123: program is normally
        !           124: also located here.  The \fBslave\fR
        !           125: program is used as the remote site's login
        !           126: shell and acts much as \fBuucico\fR in managing the
        !           127: link level communications.
        !           128: It in turn calls upon \fBsubmit\fR and \fBdeliver\fR to send and receive mail.

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