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