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1.1     ! root        1: .TH BACKUP 5
        !             2: .CT 1 sa_mortals 
        !             3: .SH NAME
        !             4: backup \- incremental backup files
        !             5: .SH DESCRIPTION
        !             6: The backup system consists of a number of client machines, and a
        !             7: `backup machine',
        !             8: which has a database and a collection of
        !             9: backup copies of files.
        !            10: On clients files concerned with backup live in a directory, normally
        !            11: .FR /usr/lib/backup ,
        !            12: defined in the shell script
        !            13: .FR /usr/bin/backup .
        !            14: The file
        !            15: .FR /usr/lib/backup/conf ,
        !            16: needed on both client and backup machine,
        !            17: has up to three lines, namely the backup machine name,
        !            18: the default backup device, and the directory, hereafter called
        !            19: .BR $FM ,
        !            20: where the rest of the backup software
        !            21: lives on the backup machine.
        !            22: Client systems normally have just the first line.
        !            23: The rest of this description applies to the backup machine.
        !            24: .PP
        !            25: The databases live in
        !            26: .BR $FM/db 
        !            27: and are maintained in
        !            28: .IR cbt (3)
        !            29: form.
        !            30: The main database, called
        !            31: .FR filemap ,
        !            32: stores two mappings.
        !            33: The first maps filename-time pairs to backup copy names, thus:
        !            34: .IP
        !            35: .EX
        !            36: /n/bowell/usr/jim/goo//519487622   v/v22/17
        !            37: .EE
        !            38: .LP
        !            39: The number after
        !            40: .CW //
        !            41: is the inode change date,
        !            42: expressed in seconds since the epoch; see
        !            43: .IR stat (2).
        !            44: If the backup copy is still on magnetic disk, it will be called
        !            45: .BR $FM/v/v22/17 ;
        !            46: otherwise it will be
        !            47: .B v22/17
        !            48: on some optical disk.
        !            49: (The mapping of backup copy name to optical disk name is kept in 
        !            50: .BR $FM/adm/volidmap .)
        !            51: The second mapping maps filenames to the time of their most recently backed-up version:
        !            52: .IP
        !            53: .L
        !            54: /n/bowell/usr/jim/goo   520514116
        !            55: .PP
        !            56: The second database,
        !            57: .BR dir ,
        !            58: maps directoryname-time pairs to the contents of that directory.
        !            59: This allows quick recovery of file trees.
        !            60: .PP
        !            61: The third database,
        !            62: .BR fs ,
        !            63: maps filename-time pairs to (essentially) inodes.
        !            64: This allows efficient implementation of 
        !            65: .BR "backup mount" ;
        !            66: see
        !            67: .IR backup (1).
        !            68: .PP
        !            69: The program
        !            70: .B $FM/bin/dbupdate
        !            71: manages these databases.
        !            72: The
        !            73: .I dir
        !            74: and
        !            75: .I fs 
        !            76: databases are optional; they will be updated only if they already exist.
        !            77: The program
        !            78: .F "$FM/bin/sweep"
        !            79: also assigns the backup copy names into a flat
        !            80: directory structure.
        !            81: A new directory is used when the total size of the files in the current directory
        !            82: would exceed 20000K
        !            83: bytes, rounding each file size up to a multiple of 4K.
        !            84: .PP
        !            85: The backup copy of a file consists of a header
        !            86: that gives the original inode, pathname and owner (as a string),
        !            87: followed by the contents of the file.
        !            88: Directories are stored as a sequence of entry names.
        !            89: .PP
        !            90: To prevent multiple writers into a database,
        !            91: a lockfile
        !            92: .FI $FM/locks/ database
        !            93: is used.
        !            94: The content of this file
        !            95: is the process id of the process accessing the database.
        !            96: Locks are removed by
        !            97: .F $FM/bin/rmlocks
        !            98: executed by
        !            99: .IR rc (8)
        !           100: when the system boots.
        !           101: .PP
        !           102: The backup system supports multiple
        !           103: .I filemap
        !           104: databases (this allows the current database to be kept small).
        !           105: The list of database names is kept in
        !           106: .FR $FM/db/filemaplist ,
        !           107: one per line in order of increasing priority.
        !           108: The last name is assumed to be the active database; all the
        !           109: others are read-only.
        !           110: .PP
        !           111: Programs such as
        !           112: .I sweep
        !           113: and
        !           114: .I dbupdate
        !           115: leave droppings in the log file
        !           116: .FR $FM/log .
        !           117: .PP
        !           118: Statistics of the numbers of files and bytes saved for users 
        !           119: of a given system are kept in
        !           120: .FR $FM/stat.dir/\fIsystem .
        !           121: Each file consists of a sequence of records with a machine-independent structure;
        !           122: generally, one record per user per day.
        !           123: The records are maintained by
        !           124: .FR "$FM/bin/procstats" ,
        !           125: which processes the file
        !           126: .F $FM/stat.log
        !           127: that is maintained by
        !           128: .IR dbupdate .
        !           129: .PP
        !           130: To allow quick searching for filenames with full regular expressions,
        !           131: a simple sorted list of all saved filenames is often kept (normally) in
        !           132: .FR $FM/filenames .
        !           133: .PP
        !           134: The device (and system) used for recovering files can be specified in many ways.
        !           135: In order of decreasing priority:
        !           136: a
        !           137: .B -f
        !           138: option in
        !           139: .I backup recover
        !           140: or
        !           141: .I backup fetch
        !           142: (see
        !           143: .IR backup (1)),
        !           144: a default device on the client system (in line 2 of
        !           145: .FR /usr/lib/backup/conf ),
        !           146: the default device on the backup system.
        !           147: .SH FILES
        !           148: .F /usr/lib/backup/*
        !           149: .br
        !           150: .F /usr/lib/backup/conf
        !           151: .br
        !           152: .F /usr/backup/db
        !           153: .br
        !           154: .F /usr/backup/locks
        !           155: .br
        !           156: .F /usr/backup/log
        !           157: .br
        !           158: .F /usr/backup/filenames
        !           159: .SH "SEE ALSO"
        !           160: .IR backup (1),
        !           161: .IR worm (8),
        !           162: .IR backup (8),
        !           163: .IR cbt (1),
        !           164: .IR stat (2)
        !           165: .br
        !           166: A. Hume,
        !           167: `The File Motel: an Owner's Manual',
        !           168: this manual, Volume 2

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