Backing up multiple user data

[Janina Sajka]

>From the book Running Linux available at BookShare:


    7.1.4) tar Tricks

   Because  tar saves the ownership and permissions of files in the
archive and retains the full directory structure, as well as symbolic
and hard links,
   using  tar  is  an  excellent  way  to  copy  or move an entire
directory tree from one place to another on the same system (or even
between different
   systems,  as  we'll  see).  Using the - syntax described earlier, you
can write a tar file to standard output, which is read and extracted on
standard
   input elsewhere.

   For  example,  say  that  we  have  a  directory containing two
subdirectories: from-stuff and to-stuff . from-stuff contains an entire
tree of files,
   symbolic  links,  and  so  forth  -- something that is difficult to
mirror precisely using a recursive cp . In order to mirror the entire
tree beneath
   from-stuff to to-stuff , we could use the commands:

cd from-stuff tar cf - . | (cd ../to-stuff; tar xvf -)

   Simple  and  elegant, right? We start in the directory from-stuff and
create a tar file of the current directory, which is written to standard
output.
   This  archive is read by a subshell (the commands contained within
parentheses); the subshell does a cd to the target directory,
../to-stuff (relative
   to from-stuff , that is), and then runs tar xvf , reading from
standard input. No tar file is ever written to disk; the data is sent
entirely via pipe
   from  one tar process to another. The second tar process has the v
option that prints each file as it's extracted; in this way, we can
verify that the
   command is working as expected.

   In  fact, you could transfer directory trees from one machine to
another (via the network) using this trick; just include an appropriate
rsh (or ssh )
   command within the subshell on the right side of the pipe. The remote
shell would execute tar to read the archive on its standard input.
(Actually,GNU
   tar has facilities to read or write tar files automatically from
other machines over the network; see the tar (1) manual page for
details.)