Using rsync to update laptop
One of my clients called for help with keeping a database on
some of his laptops current. It turns out that he has service
personnel in the field repairing appliances. Often enough they need
to order a part, but because they need to refer to a manual the
ordering was done at the end of the day. Of course the usual thing
happens - the service technician forgets what part to order, or
confuses one customer with the other and all too often the wrong
part gets ordered. Sometimes they try to order an outdated part and
the manufacturer can't fill the order. Clearly there is some room
Technology to the rescue! Most manufacturers these days provide
catalogs on CD-ROM so we installed the application on the laptop
and it worked fine. Now the service technician could look up the
model, locate the part and order the right thing.
The manufacturers usually supply just one CD-ROM which is
inconvenient if you have multiple laptops that need to be updated.
We hatched a scheme - could we install the application on a PC and
have the data files reside on a RedHat machine running Samba.
Samba, as you may know, lets your windows machines share a portion
of the disk drive in your RedHat server. Also included with Samba
is a nifty utility called rsync (
http://rsync.samba.org/download.html ). rsync lets you update a
remote machine (eg, laptop) with another machine (eg RedHat
server). We now had all the bits of the puzzle in place. Each
laptop would connect to the Local Area Network (LAN) and we would
use rsync to update the data directory on the laptop.
rsync has several features that make this an elegant solution.
First, you have to authenticate for security prposes. Second, it
uses an encrypted data stream both for authentication and for
transferring data. Third, rsync can be started by a logon script,
by a Windows desktop icon, by the cron scheduler or, in fact, by
any other scheme you can think of. Fourth, rsync can also be setup
to create new files and delete file when they disappear from the
reference machine. Finally - the coolest feature of all - rsync
will compare pieces of files on one machine to the corresponding
pieces of files on the other machine and only transfer the pieces
that are different! Brothers and Sisters that saves a ton of
bandwidth and time!!
Because you need an rsync component on each machine (it was
already installed on the RedHat machine as it is included with
Samba) I located an rsync port for windows at
followed the minimalist approach outlined there. I strayed from the
directions and it cost me several hours. Be aware that you will
need to login with a username and password that you have predefined
on the RedHat machine.
After checking the RedHat machine to make sure ssh was running
(I use WebMin) I was ready for some testing. The first time I ran
rsetup I had to set up the ssh-keys, but after that it seemed to
work fine, so I modified rsetup.bat (it could have been any .bat
file ) specific to my situation.
set CYGWIN=binmode tty
rsync -aq greatwall:/home/dhart c:\rsync
I set the username to match the login I had already set up, set
PATH and HOME to match the directory on the laptop where i
installed rsync. On the last line I typed in the name of my server
(greatwall) and the reference directory and the base target
Also, I modified the parameters a bit. I used -a which ensures
that symbolic links, devices, attributes, permissions, ownerships
and such are maintained across the transfer. The -z parameter turns
on compression, but since I was testing with binary data I didn't
bother. Using -v and -vv increases verbosity and -q decreases it.
There are many, many more options available at
I ran the bat file and entered my password. The first time
around things took a long time (it seemed like 10 minutes, but was
probably far less) (about 16 image files of 1.3 Megs each), but
when i added a couple of file to the reference directory on the
RedHat machine just to insert some change into the equation, it
took far less time.
Now when the service techs come in after a hard day repairing
icemakers and such they just jack into the LAN, double-click the
rsync icon and enter their password. They next day they are
refreshed and so is the data on their laptops.
Also see Basics: rsync
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© 2011-04-30 Dirk Hart