If you work with both a laptop and a desktop computer, you know you have to synchronize
the machines to keep them up to date. In addition, you probably want to run the
synchronization not only at your home but also from a remote site; in my case, whenever
I travel with my laptop, I make sure that whatever I do on it gets backed up to my
desktop computer. (Losing your laptop and thereby losing all your work isn't nice at all!)
Many solutions to this problem exist: This article introduces one such
rsync—and mentions several related
tools, all of which provide easy synchronization procedures.
What is rsync?
rsync utility is a file-transfer and synchronization
program widely available for Linux® and UNIX® and even ported to
Windows®. Its key feature is a very fast algorithm that just sends file
differences over the data link, thus minimizing the total data flow between
machines. (If you use the File Transfer Protocol [FTP] or utilities such as
scp, complete files
will be sent, even if just one byte has changed.) Of course,
isn't limited to existing files: It can also deal with files and directories that
might be present only at one end of the link. Finally, communications are optimized
by compressing data, so you can use the tool even without a broadband connection.
Getting and installing rsync
You can get precompiled binary packages for most current Linux distributions,
and this is the first thing you should check. I use Smart for package
management with OpenSUSE, and
sudo smart install rsync
was all I needed to install
rsync's latest version.
If you are a die-hard compile-everything fan, you can get the source code
(see Resources for a link) and install it with
configure, make, make install method;
check the included README file for detailed instructions.
For secure communications, you will want to have Secure Shell (ssh) installed. (You could use remote shell [rsh], but it's nowhere near as secure.) OpenSSH, a free implementation of ssh, is commonly available with all distributions. You will also need to open a port in your firewall so that your computers can connect with each other. All this configuration is standard: Check Resources for links to more information.
So, let's start using
rsync and directly synchronize your
laptop with a remote server. To do so, you use code similar to that shown in
Listing 1. You can also synchronize your remote server to
your laptop (files will be sent over from the server to your laptop) or even two
local directories, but not two remote servers.
Listing 1. Two versions of the same complete rsync command
rsync --compress --recursive --delete --links \ --times --perms --owner --group \ --verbose --progress --stats \ --rsh="ssh" \ --exclude "*bak" --exclude "*~" \ /my/path/at/the/laptop/* myserver:/some/path/at/the/server rsync -zrltpogve "ssh" --progress --stats --delete \ --exclude "*bak" --exclude "*~" \ /my/path/at/the/laptop/* myserver:/some/path/at/the/server
Note that the order of the options in Listing 1 is arbitrary, and most have a shorter
-z) specifies that data will be compressed, saving
bandwidth in the process. You should always include this option. (It can be argued
that over a very high-speed data link, you might do without compression, but for
most remote connection links, compression will help.) A complementary option,
--compress-level=level can be used to specify
different levels of compression; however, the standard compression level is typically
rsync copy all directories recursively. All files
within a directory, including possibly other directories and their own contents,
will be copied. If you don't happen to need this functionality, the
-d) provides the opposite effect: Directories and
their contents will be skipped.
rsync copies needed files to the destination
computer but won't delete extra files there. By using the
option, the destination directory will be exactly like the original one. Be careful,
though: If you ever happen to sync an empty file with a remote directory, you will
delete everything at the remote machine directory!
If there are symlinks in your original directory, the
-l) recreates those symlinks in the
destination directory. As an alternative,
-L copies the item the symlink points to instead of the
symlink itself. If you have symlinks that point outside the copied tree (a safety risk),
you can use
--copy-unsafe-links instead. The
--safe-links option provides a safer method, ignoring
The next four options—
keep the original update timestamp, permission, owner, and group details,
respectively. An easier way to specify all these options is by using
-a, which also
The three following options (
--stats) provide lots of information as to what
rsync is doing. If you are not interested, just skip
rsync will be quiet unless an error pops up.
rsync versions default to using ssh, the
-e) option lets
you force its usage. If you happened to require extra parameters for ssh (say, if
you had set up ssh to use a non-standard port), you can add them, as in
--rsh "ssh -p 12345".
--exclude option (and its sibling,
lets you be more selective as to which files to synchronize. In this example, I
excluded common backup files. Exclude and include files as desired to optimize
what's sent over.
Finally, specify both the source and the destination paths, and you are done! Don't
forget the final
/*, or the result might not be as
desired. If you check the documentation, you can find out the difference between
some/path, some/path/, and some/path/*. But using
is the safest way out.
You can shorten the command from Listing 1 by using the
--archive), as shown in Listing 2.
(For purists, the
-a option can copy some extra
elements—check the documentation—but only if you are running
rsync as root in the server, which isn't a secure thing
to do anyway.) There are far more options; check
man rsync for a complete list.
Listing 2. A shorter, more silent version of the same command
rsync -zae "ssh" --delete --exclude "*bak" --exclude "*~" \ /my/path/at/the/laptop/* myserver:/some/path/at/the/server
If you'd rather use a graphical user interface (GUI) instead of the command line, there are several possibilities. However, you should keep in mind that there's no "perfect alternative" and that you should do some thorough testing before committing to any program in particular. Some programs are in development (though they look interesting enough to include them in this review), and some are more advanced in their capabilities. (There also are some duds, which I include as a warning!)
GAdmin-Rsync (shown in Figure 1) is part of the Gadmintools
package, a set of GPL-licensed GUI tools for Linux systems administration. Its
latest version is a surprisingly low 0.1.1 from January 2009, while the previous
version was 0.1.0 from June 2008. Installation is quite simple: If you don't
find a distribution-ready package, it's just a matter of downloading the source
code and running a simple
Figure 1. Despite its low version number, GAdmin-Rsync promises good functionality, though its interface needs more development.
A small surprise was that the program requires the root password. Call me safety conscious, but I certainly don't like working as root unless I have to; mistakes are usually costlier for the root user!
The first time you use this tool, it asks for details about the backup you want to run. GAdmin-Rsync allows you to define several backups, so it's easier to re-run them. You need to specify the kind of backup (local to local, local to remote, or remote to local) and the appropriate directories and server data. But be careful here: I didn't find a way to edit the server parameters, so fixing them would require creating a new backup—not too user friendly. I also met another problem: The program wouldn't accept a password-less connection.
There are not many frills in GAdmin-Rsync. For example, you cannot just do a "dry
run." In contrast, there's an easy way to specify
jobs to be run at later times. Probably, this functionality reflects the "root-oriented"
idea of the program: It's not for casual users but for systems administrators.
(The Help feature agrees with this: It just says "Howto backup using GAdmin-Rsync:
Visit http://www.gadmintools.org"—just a notch above a "RTFM" comment!)
How much you will like this program depends on your systems administrator bent,
but it can be useful.
Grsync (shown in Figure 2) is a GTK-based GUI for rsync, but it isn't limited to Gnome. Its latest version is 0.6.2, dated December 2008, which means that the program is still supported and in development. Among its most interesting features are:
- Saving your settings as "sessions" so that you can easily re-run a backup procedure.
- Allowing a "simulation" (dry run) before actually committing to the backup.
- Executing extra commands before and after the backup job.
- Including a command-line version,
grsync-batch, that lets you run Grsync sessions from a
cron-scheduled run, for example.
Figure 2. Grsync doesn't offer too many of the options of the underlying rsync command but is quite usable and stable.
At the home page (see Resources for a link), you will
find only source code, which you can compile on your own if you have GTK and
Autotools. However, you can find ready-made binaries for many distributions,
including OpenSUSE, Mandriva, Red Hat (and Fedora and CentOS, as well), and
more. Grsync is just a front end, so it doesn't include
You will have to install that on your own first.
rsync features are available, but for most users,
the included options will be enough. If you need something, click the Advanced
Options tab, and you will be able to add any option you require. Be careful
with the syntax, though: If you make a mistake, Grsync won't complain, but
rsync will, and you will get its error message when
you try to execute the backup. Other than that, the package is quite usable and
stable—probably the best of all the GUIs I reviewed.
QSync and TKsync
QSync is a Qt-based interface, but its development seems to have stopped at version
0.3, from December 2005. I won't recommend this tool: It requires its own
rsync version, so it won't use your specific,
rsync package but rather the internal
(certainly old) version of the command. I downloaded an OpenSUSE package,
but it wouldn't run, and frankly, it didn't seem worthwhile trying a custom
build for a seemingly abandoned package. The author himself admitted (in
2003) that "The syncing portion of QSync isn't quite right yet," and because
there have been no updates since then, it stands to reason that this problem
hasn't been solved.
Running a Google search for
rsync GUIs might lead
you to another project—TKsync—whose latest version (0.2.1)
was released in 2004. Searching, however, failed to get the (apparently deleted)
project page. So, it's fairly safe to call this project dead. If you happen to find
an installation package, you'd probably be better off ignoring it.
Even with Zynk being (obviously) at the beginning of its development cycle, the program looks promising enough to mention. Also, you might find versions of it for several distributions, and you should be aware of its (current) limitations. Finally, note that Zynk is a GTK+ application but can be run without Gnome; in particular, I ran my tests under the K Desktop Environment (KDE).
As to development status, Zynk is currently at version 0.0.2, dated February 2009, and the author himself warns, "There are hundreds of bugs at the moment! Only some parts of the software work as expected! USE AT YOUR OWN RISK!" On his estimate, the program is only about 10 percent done, though it looks like it is more complete than that, as Figure 3 shows.
Figure 3. Zynk is at the beginning of its development cycle but looks promising.
Zynk apparently provides for most (if not all) of the
options. (By the way, you need have
installed.) At the bottom of the window, you can see the command that will be
executed and its output.
Having run some tests, I must agree that the program needs more work. But unlike QSync, it seems like development is ongoing, so there's a reasonable chance that the program will actually become usable.
rsync utility is a mandatory tool for your command-line
work, and you need to learn how to use it for easy, safe, quick laptop-desktop
synchronization. If a GUI is more your thing, Grsync seems the best option available
today, as QSync is badly outdated and both GAdmin-Rsync and Zynk are at the
beginning of their development cycles.
Andrew Tridgell wrote about
rsyncin his Ph.D. dissertation, "Efficient Algorithms for Sorting and Synchronization," and provided a more specific description in his technical report on the
rsyncsite is a mandatory visit. It features a good FAQ as well as documentation and examples, among other resources.
- The AIX and UNIX developerWorks zone provides a wealth of information relating to all aspects of IBM® AIX® systems administration and expanding your UNIX skills.
- New to AIX and UNIX? Visit the New to AIX and UNIX page to learn more.
- Check the Unison Web site for more on this program, or this article I wrote some time ago, for a more hands-on view.
- Browse the technology bookstore for books on this and other technical topics.
Get products and technologies
- Read up on ssh, and install OpenSSH (a free version of ssh) for secure communications.
rsyncand install it.
- GAdmin-Rsync is a part of the Gadmintools package, a set of GUI tools for Linux systems administrators.
- Grsync is still being updated and, though a bit limited, is quite usable.
- Krsync is built upon Kommander, a visual scripting tool for Linux.
- QSync is dated and probably abandoned; I'd suggest staying away from it.
- Zynk looks interesting, though it's at an early stage and not ready yet.
- Use Smart for package management.
- Check out developerWorks blogs and get involved in the developerWorks community.
- Participate in the AIX and UNIX forums:
Dig deeper into AIX and Unix on developerWorks
Get samples, articles, product docs, and community resources to help build, deploy, and manage your cloud apps.
Experiment with new directions in software development.
Software development in the cloud. Register today to create a project.
Evaluate IBM software and solutions, and transform challenges into opportunities.