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NAME
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rdarena, wrarena – copy arenas between venti servers
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SYNOPSIS
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venti/rdarena [ −qv ] arenapart arenaname
venti/wrarena [ −o fileoffset ] [ −h host ] arenafile [ clumpoffset
]
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DESCRIPTION
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Rdarena extracts the named arena from the arena partition arenapart
and writes this arena to standard output. This command is typically
used to back up an arena to external media. The −v option generates
more verbose output on standard error; −q generates only errors
on standard error.
Wrarena writes the blocks contained in the arena arenafile (typically,
the output of rdarena) to a Venti server. It is typically used
to reinitialize a Venti server from backups of the arenas. For
example,
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venti/rdarena /dev/sdC0/arenas arena.0 >external.media
venti/wrarena −h venti2 external.media
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writes the blocks contained in arena.0 to the Venti server venti2
(typically not the one using /dev/sdC0/arenas).
The −o option specifies that the arena starts at byte fileoffset
(default 0) in arenafile . This is useful for reading directly
from the Venti arena partition:
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venti/wrarena −h venti2 −o 335872 /dev/sdC0/arenas
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(In this example, 335872 is the offset shown in the Venti server’s
index list (344064) minus one block (8192). You will need to substitute
your own arena offsets and block size.)
Finally, the optional offset argument specifies that the writing
should begin with the clump starting at offset within the arena.
Wrarena prints the offset it stopped at (because there were no
more data blocks). This could be used to incrementally back up
a Venti server to another Venti server:
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last=`{cat last}
venti/wrarena −h venti2 −o 335872 /dev/sdC0/arenas $last >output
awk '/^end offset/ { print $3 }' offset >last
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Of course, one would need to add wrapper code to keep track of
which arenas have been processed. See /sys/src/cmd/venti/words/backup.example
for a version that does this.
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SOURCE
SEE ALSO
BUGS
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Wrarena can’t read a pipe or network connection containing an
arena; it needs a file already containing the entire arena.
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