177 lines
4 KiB
Plaintext
177 lines
4 KiB
Plaintext
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.TH VAC 1
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.SH NAME
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vac, unvac \- create, extract a vac archive on Venti
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.SH SYNOPSIS
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.B vac
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[
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.B -mqsv
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] [
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.B -b
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.I blocksize
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] [
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.B -d
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.I oldvacfile
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] [
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.B -e
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.I exclude
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] [
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.B -f
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.I vacfile
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] [
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.B -i
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.I name
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] [
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.B -h
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.I host
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]
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.I file ...
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.PP
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.B unvac
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[
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.B -Tctv
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] [
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.B -h
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.I host
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]
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.I vacfile
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[
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.I file ...
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]
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.SH DESCRIPTION
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.I Vac
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creates an archival copy of Plan 9 file trees on Venti. It can be used
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to build a simple backup system. One of the unusual properties of Venti is
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that duplicate blocks are detected and coalesced. When
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.I vac
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is used on a file tree that shares data with an existing archive, the consumption of
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storage will be approximately equal to an incremental backup.
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This reduction in storage consumption occurs transparently to the user.
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.PP
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As an optimization, the
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.B -d
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and
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.B -q
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options, described below, can be used to explicitly create an archive relative to an existing archive.
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These options do not change the resulting archive generated by
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.IR vac ,
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but simply reduce the number of write operations to Venti.
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.PP
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The output of
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.I vac
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is the hexadecimal representation of the SHA1 fingerprint of the root of the archive, in this format:
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.IP
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.EX
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vac:64daefaecc4df4b5cb48a368b361ef56012a4f46
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.EE
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.PP
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The options to
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.I vac
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are:
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.TF "-d\fI oldvacfile"
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.PD
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.TP
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.BI -b " blocksize
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Specifies the block size that data will be broken into.
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The units for the size can be specified by appending
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.L k
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to indicate kilobytes.
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The default is 8k.
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The size must be in the range
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of 512 bytes to 52k.
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.TP
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.BI -d " oldvacfile
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Reduce the number of blocks written to Venti by comparing the files to be stored with
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the contents of an existing
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.I vac
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file tree whose score is stored in
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.IR oldvacfile .
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.TP
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.BI -e " exclude
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Do not include the file or directory specified by
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.IR exclude .
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This option may be repeated multiple times.
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.TP
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.BI -f " vacfile
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The results of
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.I vac
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are placed in
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.IR vacfile ,
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or the standard output if no file is given.
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.TP
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.BI -i " name
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Include standard input as one of the input files, storing it in the archive
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with the specified
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.IR name .
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.TP
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.BI -h " host
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The network address of the Venti server.
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The default is taken from the environment variable
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.BR venti .
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If this variable does not exist, then the default is the
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metaname
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.BR $venti ,
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which can be configured via
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.IR ndb (6).
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.TP
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.B -m
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Expand and merge any
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.I vac
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archives that are found while reading the input files. This option is
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useful for building an archive from a collection of existing archives. Each archive is inserted
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into the new archive as if it had been unpacked in the directory in which it was found. Multiple
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archives can be unpacked in a single directory and the contents will be merged. To be detected, the
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archives must end in
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.LR .vac .
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Note, an archive is inserted by simply copying the root fingerprint and does not require
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the archive to be unpacked.
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.TP
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.B -q
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Increase the performance of the
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.B -d
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option by detecting unchanged files based on a match of the files name and other meta data,
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rather than examining the contents of the files.
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.TP
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.B -s
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Print out various statistics on standard error.
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.TP
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.B -v
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Produce more verbose output on standard error, including the name of the files added to the archive
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and the vac archives that are expanded and merged.
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.PP
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.I Unvac
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lists or extracts files stored in the vac archive
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.IR vacfile ,
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which can be either a vac archive string in the format
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given above or the name of a file containing one.
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If
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.I file
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arguments are given, only those files or directories
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will be extracted.
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The options are:
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.TP
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.B -T
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Set the modification time on extracted files
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to the time listed in the archive.
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.TP
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.B -c
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Write extracted files to standard output instead of creating a file.
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.TP
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.B -h
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as per
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.IR vac .
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.TP
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.B -t
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Print a list of the files to standard output rather than extracting them.
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.TP
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.B -v
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If extracting files, print the name of each file and directory
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to standard error.
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If listing files, print metadata in addition to the names.
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.SH SOURCE
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.B /sys/src/cmd/vac
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.br
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.B /sys/src/cmd/unvac
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.SH "SEE ALSO"
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.IR vacfs (4),
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.IR venti (8)
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