venti-backup 2.2 KB

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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 /sys/src/cmd/venti/srv
  106. .SH SEE ALSO
  107. .IR venti (6),
  108. .IR 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.