rsync is an excellent and versatile backup tool, but it does have one drawback: you have to run it manually when you want to back up your data. Sure, you can use cron to create scheduled backups, but even this solution cannot provide seamless live synchronization. If this is what you want, then you need the lsyncd tool, a command-line utility which uses rsync to synchronize (or rather mirror) local directories with a remote machine in real time. To install lsyncd on your machine, download the latest .tar.gz archive from the project's Web site, unpack it, and use the terminal to switch to the resulted directory. Run then the ./configure command followed by make, and make install (the latter command requires root privileges). lsyncd is rather straightforward in use, as it features just one command and a handful of options. The lsyncd command requires only two parameters: the source and the target directory, for example:

lsyncd /path/to/source /path/to/target

This command syncs two local directories, but lsyncd can also mirror a local directory to a folder on a remote machine. For example, the following command syncs the source directory on the local machine with the target directory on a remote machine which has the 192.168.1.7 IP address, connecting to the remote server as the user "monkey":

lsyncd /path/to/source monkey@192.168.1.7:/path/to/target/

In most cases, you have to provide a password to successfully connect to a remote server, so to make the command above work, you have to use the --no-daemon option which prevents the process from running as a daemon:

lsyncd --no-daemon /path/to/source monkey@192.168.1.7:/path/to/target/

Another useful option is --exclude. As the name suggests, it allows you to specify files or directories that you don't want to sync.