185 lines
5.0 KiB
Groff
185 lines
5.0 KiB
Groff
.TH REMSYNC 1
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.SH NAME
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remsync - remotely synchronize file trees
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.SH SYNOPSIS
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.B remsync
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.B \-sxv
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.I tree
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.RI [ state-file ]
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.br
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.B remsync
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.B \-duxvD
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.I tree
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.RI [ state-file
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.RI [ diff-file ]]
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.br
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.B remsync
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.RB [ \-xv ]
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.I tree
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.RI [ diff-file ]
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.SH DESCRIPTION
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.de SP
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.if t .sp 0.4
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.if n .sp
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..
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.B Remsync
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synchronizes file trees of distant machines, i.e. machines that do not have
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a fast network between them. It accomplishes this in three steps:
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.PP
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.RS
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Create a state file containing a description of the machine to be updated.
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.RE
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.PP
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.RS
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Compute a file of differences on the source machine using the state file to
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compare the two file trees.
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.RE
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.PP
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.RS
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Update the target machine using the data in the differences file.
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.RE
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.PP
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This process requires that you move two files, a state file from the target
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machine to the source machine, and a differences file from the source
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machine to the target machine. The state file is an ASCII file that may be
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edited, usually to make
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.B remsync
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ignore some files or file trees.
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.PP
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The argument
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.I tree
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may be a single file or a directory. A directory is traversed recursively.
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The
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.I state-file
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and
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.I diff-file
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arguments may be of any file type. The differences file contains an end
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marker, so it may be followed by trailing junk. Standard input or
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output is used if these arguments are omitted or replaced by a minus
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sign.
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.SS "State file format"
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A state file has a line for each file in a tree. A line looks like this
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formally for a simple file:
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.PP
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.RS
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.I "name mode owner group length date"
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.RI [ link-number
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.RB [ last ]]
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.RE
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.PP
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The best way to show how each type of file is represented is by example:
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.PP
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.RS
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.nf
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.ta +10 +8 +4 +4 +6 +12 +4
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/ d755 0 0
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bin d755 2 0
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.in +2
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[ 644 2 0 233 759160857 1
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cat 755 2 0 3772 768742021
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test 755 2 0 233 759160857 1 last
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.in -2
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dev d755 0 0
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.in +2
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fd0 b666 0 0 200
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console c600 10 0 400
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sd2 b600 0 0 a02
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fifo p700 2 0
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.in -2
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opt -> usr/opt
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usr ignore (Cross-device link)
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.fi
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.RE
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.PP
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The root of the tree is always represented by a /, no matter what type of
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file it may be. Directory entries of the root follow at the same level.
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Files in subdirectories are indented by two spaces. (Eight spaces are
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replaced by a TAB.) Normal files have their length and modified time in the
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state file, devices have their device number in hex, etc. If files are hard
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linked to each other then they all get an extra "link number" to bind them
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together. The last link is marked with the word
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.BR last .
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.PP
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One usually only modifies a state file to ignore differences between two
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files. One does this by replacing the file attributes with the word
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.BR ignore .
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.RB ( Remsync
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generates this keyword too, with the reason why added in parentheses.)
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.SH OPTIONS
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.TP
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.B \-s
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Generate a state file.
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.TP
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.B \-d
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Generate a differences file. (The default is to apply a differences file.)
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.TP
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.B \-u
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Only add new files or update files with newer versions.
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.TP
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.B \-x
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Do not cross device boundaries. This allows one to operate on the root file
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system for instance ignoring the
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.B /usr
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file system.
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.TP
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.B \-D
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Debug differences file generation. With this flag no file contents are
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added to the differences file. The result is then human readable.
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.TP
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.B \-v
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Lists the commands added to the differences file, or the actions done
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applying a differences file. The output looks like \s-2UNIX\s+2 commands
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except for the words "add", "restore" and "update" indicating addition of a
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new file, replacing a file with an older version, or replacement by a newer
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version.
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.SH EXAMPLES
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Actions taken by the author to update his notebook "finiah" from his main
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machine "darask":
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.PP
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.RS
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.nf
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finiah# remsync -s /usr /tmp/finiah.state
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.SP
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Edit the state file to ignore .Xauthority files and /usr/var.
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.SP
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finiah# tar cvf /dev/fd0 /tmp/finiah.state
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.SP
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darask# tar xvf /dev/fd0
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.br
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darask# remsync -dv /usr /tmp/finiah.state | vol 1440 /dev/fd0
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.SP
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finiah# vol 1440 /dev/fd0 | remsync -v /usr
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.fi
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.RE
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.PP
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One could add a file compression/decompression program between
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.B remsync
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and
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.BR vol ,
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to reduce the number of floppies to move about, but that actually slows
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things down! (Note that one only needs to shuffle two floppies about if the
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two machines are adjacent. To update a remote machine it does make sense to
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use compression to reduce the number of floppies to carry.)
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.SH "SEE ALSO"
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.BR synctree (1),
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.BR vol (1),
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.BR tar (1).
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.SH NOTES
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Nothing stops you from using
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.B remsync
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over a fast network of course.
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.B Synctree
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can be a bit tedious if you only want to ignore a few files. Editing a
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state file is then easier.
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.SH BUGS
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Files are overwritten, not removed, when they are updated. This means
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that links outside the tree are also updated. The less desirable
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alternative to this is to break the link before the update.
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.PP
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The verbose option may say that a link is to be created when making a
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differences file. The link is often already there when the update takes
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place, so no action is taken, and thus no talk about it. So you may miss a
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few mutterings about links if you compare the messages.
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.SH AUTHOR
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Kees J. Bot (kjb@cs.vu.nl)
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