3 read, write, copy \- simple Venti clients
41 Venti is a SHA1-addressed block storage server.
44 for a full introduction.
47 reads a block with the given
53 and prints the block to standard output.
58 consults the environment variable
60 for the name of the Venti server.
65 will try each type, one at a time, until it finds
67 It prints the corresponding
70 command to standard error
71 to indicate the type of the block.
74 writes at most 56 kilobytes of data from standard input
77 and prints the resulting score to standard output.
83 denoting a data block.
88 zero truncates the block before writing it to the server.
96 It copies the entire tree of blocks reachable from
97 the root block from the server
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).
107 runs more efficiently if it does not copy blocks
108 (and all their children) multiple times.
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.
119 to maintain an in-memory list of blocks it has copied
120 and avoid considering the same block multiple times.
123 option is only useful if the destination Venti server is
124 known not to have lost any blocks due to disk corruption
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.
138 reaction to errors reading
142 always prints information to standard error
143 about each read error.
146 exits after printing the first error.
149 option is given, read errors are ignored.
150 This is dangerous behavior because it breaks the
151 assumption made by `fast' mode.
156 replaces pointers to unreadable blocks with
157 pointers to the zero block.
158 It writes the new root score to standard output.
161 option prints scores as it copies them, total writes, and other
162 debugging information.
165 option prints debugging information about the Venti protocol
166 messages send/received.
178 There should be programs to read and write
179 venti files and directories.