tventi-backup.8 - plan9port - [fork] Plan 9 from user space
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       tventi-backup.8 (2290B)
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            1 .TH VENTI-BACKUP 8
            2 .SH NAME
            3 rdarena, wrarena \- copy arenas between venti servers
            4 .SH SYNOPSIS
            5 .PP
            6 .B venti/rdarena
            7 [
            8 .B -qv
            9 ]
           10 .I arenapart
           11 .I arenaname
           12 .PP
           13 .B venti/wrarena
           14 [
           15 .B -o
           16 .I fileoffset
           17 ]
           18 [
           19 .B -h
           20 .I host
           21 ]
           22 .I arenafile
           23 [
           24 .I clumpoffset
           25 ]
           26 .SH DESCRIPTION
           27 .PP
           28 .I Rdarena
           29 extracts the named
           30 .I arena
           31 from the arena partition
           32 .I arenapart
           33 and writes this arena to standard output.
           34 This command is typically used to back up an arena to external media.
           35 The
           36 .B -v
           37 option generates more verbose output on standard error;
           38 .B -q
           39 generates only errors on standard error.
           40 .PP
           41 .I Wrarena
           42 writes the blocks contained in the arena
           43 .I arenafile
           44 (typically, the output of
           45 .IR rdarena )
           46 to a Venti server.
           47 It is typically used to reinitialize a Venti server from backups of the arenas.
           48 For example,
           49 .IP
           50 .EX
           51 venti/rdarena /dev/sdC0/arenas arena.0 >external.media
           52 venti/wrarena -h venti2 external.media
           53 .EE
           54 .LP
           55 writes the blocks contained in
           56 .B arena.0
           57 to the Venti server
           58 .B venti2
           59 (typically not the one using
           60 .BR /dev/sdC0/arenas ).
           61 .PP
           62 The
           63 .B -o
           64 option specifies that the arena starts at byte
           65 .I fileoffset
           66 (default
           67 .BR 0 )
           68 in
           69 .I arenafile .
           70 This is useful for reading directly from
           71 the Venti arena partition:
           72 .IP
           73 .EX
           74 venti/wrarena -h venti2 -o 335872 /dev/sdC0/arenas
           75 .EE
           76 .LP
           77 (In this example, 335872 is the offset shown in the Venti
           78 server's index list (344064) minus one block (8192).
           79 You will need to substitute your own arena offsets
           80 and block size.)
           81 .PP
           82 Finally, the optional
           83 .I offset
           84 argument specifies that the writing should begin with the
           85 clump starting at
           86 .I offset
           87 within the arena.
           88 .I Wrarena
           89 prints the offset it stopped at (because there were no more data blocks).
           90 This could be used to incrementally back up a Venti server
           91 to another Venti server:
           92 .IP
           93 .EX
           94 last=`{cat last}
           95 venti/wrarena -h venti2 -o 335872 /dev/sdC0/arenas $last >output
           96 awk '/^end offset/ { print $3 }' offset >last
           97 .EE
           98 .LP
           99 Of course, one would need to add wrapper code to keep track
          100 of which arenas have been processed.
          101 See
          102 .B /sys/src/cmd/venti/words/backup.example
          103 for a version that does this.
          104 .SH SOURCE
          105 .B \*9/src/cmd/venti/srv
          106 .SH SEE ALSO
          107 .MR venti (7) ,
          108 .MR venti (8)
          109 .SH BUGS
          110 .I Wrarena
          111 can't read a pipe or network connection containing an arena;
          112 it needs a file already containing the entire arena.