VENTI(1) VENTI(1)
NAME
read, write, copy - simple Venti clients
SYNOPSIS
venti/read [ -h host ] [ -t type ] score
venti/write [ -z ] [ -h host ] [ -t type ]
venti/copy [ -fimrVv ] [ -t type ] srchost dsthost score
DESCRIPTION
Venti is a SHA1-addressed block storage server. See
venti(7) for a full introduction.
Read reads a block with the given score and numeric type
from the server host and prints the block to standard out-
put. If the -h option is omitted, read consults the envi-
ronment variable $venti for the name of the Venti server.
If the -t option is omitted, read will try each type, one at
a time, until it finds one that works. It prints the corre-
sponding read -t command to standard error to indicate the
type of the block.
Write writes at most 56 kilobytes of data from standard
input to the server host and prints the resulting score to
standard output. If the -t option is omitted, write uses
type 0, denoting a data block. If the -z option is given,
write zero truncates the block before writing it to the
server.
Copy expects score to be the score of a VtRoot block. It
copies the entire tree of blocks reachable from the root
block from the server srchost to the server dsthost.
Venti's blocks are arranged in a directed acyclic graph (see
venti(6)); there may be multiple paths from a root score to
an interior block (for example, if the same file contents
are stored under multiple names in an archive). Copy runs
more efficiently if it does not copy blocks (and all their
children) multiple times. The -f option causes copy to
assume that if a block already exists on the destination
Venti server, all its children also exist and need not be
considered. The -m option causes copy to maintain an in-
memory list of blocks it has copied and avoid considering
the same block multiple times. The -f option is only useful
if the destination Venti server is known not to have lost
any blocks due to disk corruption or other failures. The -m
option is only useful if enough memory is available to hold
the block list, which typically requires about 1% of the
total number of bytes being copied.
The -i and -r options control copy's reaction to errors
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VENTI(1) VENTI(1)
reading from srchost. Copy always prints information to
standard error about each read error. By default, copy
exits after printing the first error. If the -i option is
given, read errors are ignored. This is dangerous behavior
because it breaks the assumption made by `fast' mode. If
the -r option is given, copy replaces pointers to unreadable
blocks with pointers to the zero block. It writes the new
root score to standard output. The -v option prints scores
as it copies them, total writes, and other debugging infor-
mation. The -V option prints debugging information about
the Venti protocol messages send/received.
SOURCE
/usr/local/plan9/src/cmd/venti
SEE ALSO
vac(1), venti(3), vacfs(4), venti(7), vbackup(8), venti(8),
venti-fmt(8)
BUGS
There should be programs to read and write venti files and
directories.
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