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	tventi.1 - plan9port - [fork] Plan 9 from user space
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	tventi.1 (3258B)
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	1 .TH VENTI 1
	2 .SH NAME
	3 read, write, copy \- simple Venti clients
	4 .SH SYNOPSIS
	5 .B venti/read
	6 [
	7 .B -h
	8 .I host
	9 ]
	10 [
	11 .B -t
	12 .I type
	13 ]
	14 .I score
	15 .br
	16 .B venti/write
	17 [
	18 .B -z
	19 ]
	20 [
	21 .B -h
	22 .I host
	23 ]
	24 [
	25 .B -t
	26 .I type
	27 ]
	28 .br
	29 .B venti/copy
	30 [
	31 .B -fimrVv
	32 ]
	33 [
	34 .B -t
	35 .I type
	36 ]
	37 .I srchost
	38 .I dsthost
	39 .I score
	40 .SH DESCRIPTION
	41 Venti is a SHA1-addressed block storage server.
	42 See
	43 .MR venti (7)
	44 for a full introduction.
	45 .PP
	46 .I Read
	47 reads a block with the given
	48 .I score
	49 and numeric
	50 .I type
	51 from the server
	52 .I host
	53 and prints the block to standard output.
	54 If the
	55 .B -h
	56 option is omitted,
	57 .I read
	58 consults the environment variable
	59 .B $venti
	60 for the name of the Venti server.
	61 If the
	62 .B -t
	63 option is omitted,
	64 .I read
	65 will try each type, one at a time, until it finds
	66 one that works.
	67 It prints the corresponding
	68 .B read
	69 .B -t
	70 command to standard error
	71 to indicate the type of the block.
	72 .PP
	73 .I Write
	74 writes at most 56 kilobytes of data from standard input
	75 to the server
	76 .I host
	77 and prints the resulting score to standard output.
	78 If the
	79 .B -t
	80 option is omitted,
	81 .I write
	82 uses type 0,
	83 denoting a data block.
	84 If the
	85 .B -z
	86 option is given,
	87 .I write
	88 zero truncates the block before writing it to the server.
	89 .PP
	90 .I Copy
	91 expects
	92 .I score
	93 to be the score of a
	94 .B VtRoot
	95 block.
	96 It copies the entire tree of blocks reachable from
	97 the root block from the server
	98 .I srchost
	99 to the server
	100 .IR dsthost .
	101 .PP
	102 Venti's blocks are arranged in a directed acyclic graph (see venti(6));
	103 there may be multiple paths from a root score to an
	104 interior block (for example, if the same file contents are stored
	105 under multiple names in an archive).
	106 .I Copy
	107 runs more efficiently if it does not copy blocks
	108 (and all their children) multiple times.
	109 The
	110 .B -f
	111 option causes
	112 .I copy
	113 to assume that if a block already exists on the destination
	114 Venti server, all its children also exist and need not be considered.
	115 The
	116 .B -m
	117 option causes
	118 .I copy
	119 to maintain an in-memory list of blocks it has copied
	120 and avoid considering the same block multiple times.
	121 The
	122 .B -f
	123 option is only useful if the destination Venti server is
	124 known not to have lost any blocks due to disk corruption
	125 or other failures.
	126 The
	127 .B -m
	128 option is only useful if enough memory is available to
	129 hold the block list, which typically requires about 1%
	130 of the total number of bytes being copied.
	131 .PP
	132 The
	133 .B -i
	134 and
	135 .B -r
	136 options control
	137 .IR copy 's
	138 reaction to errors reading
	139 from
	140 .IR srchost .
	141 .I Copy
	142 always prints information to standard error
	143 about each read error.
	144 By default,
	145 .I copy
	146 exits after printing the first error.
	147 If the
	148 .B -i
	149 option is given, read errors are ignored.
	150 This is dangerous behavior because it breaks the
	151 assumption made by `fast' mode.
	152 If the
	153 .B -r
	154 option is given,
	155 .I copy
	156 replaces pointers to unreadable blocks with
	157 pointers to the zero block.
	158 It writes the new root score to standard output.
	159 The
	160 .B -v
	161 option prints scores as it copies them, total writes, and other
	162 debugging information.
	163 The
	164 .B -V
	165 option prints debugging information about the Venti protocol
	166 messages send/received.
	167 .SH SOURCE
	168 .B \*9/src/cmd/venti
	169 .SH SEE ALSO
	170 .MR vac (1) ,
	171 .MR venti (3) ,
	172 .MR vacfs (4) ,
	173 .MR venti (7) ,
	174 .MR vbackup (8) ,
	175 .MR venti (8) ,
	176 .MR venti-fmt (8)
	177 .SH BUGS
	178 There should be programs to read and write
	179 venti files and directories.