As I mentioned before, Dropbox is a fantastic service to sync, backup, share and publish our files over the Internet. It provides free Cloud storage between 2GB-10GB and many prefer Dropbox than Windows Live Mesh 2011 for more flexibility and interoperability.
However, the files/folders must reside in the local Dropbox folder in order for them to be able to sync, backup, share and/or publish with Dropbox service.
Anyhow, it is easy to sync the folders outside Dropbox folder, with the use of symbolic link (a.k.a. symlink or softlink).
Note: Symbolic link is not available in Windows 2003, Windows XP or earlier, but you can use Junction to serve the same purpose. You can download the Junction.exe utility made available by SysInternals here.
Example: To let Dropbox to sync the folder C:\Users\Public\Documents in Windows.
Step 1: Run Command Prompt with Administrator rights. The Administrator rights is required to make symbolic link in Windows Vista or Windows 7.
To do this, click on Start logo, expand All programs > Accesories and right click on Command Prompt. Then select "Run as administrator".
Step 2: Move the entire folder into your Dropbox folder.
C:> move C:\Users\Public\Documents C:\Users\Myself\Dropbox
Step 3: Create a directory symbolic link (or junction for Win XP/2000/2003) at the original location to link to the folder which moved into Dropbox folder.
For Win Vista or Win 7 or above:
C:> mklink /d C:\Users\Public\Documents C:\Users\Myself\Dropbox\Documents
Note: The "/d" option is for making directory/folder link. Otherwise, the command will create a file link.
For Win XP or Win 2003 or below:
C:> junction C:\Users\Public\Documents C:\Users\Myself\Dropbox\Documents
You are done. Now, the Documents is synchronized in your Dropbox account, at the same time, you can still access it from its original location as normal.
Example: To let Dropbox to sync the folder /home/Myself/Documents in Linux/Unix.
Step 1: Open the Terminal window if you are in X-Window. For Ubuntu, it is in Applications > Accesories > Terminal.
Step 2: Move the entire folder into your Dropbox folder.
$ mv /home/Myself/Documents /home/Dropbox/Documents
If you don't have write permission in /home/Dropbox directory, you might want to use chmod to set the permission correctly, or use sudo to perform the move with root permission.
$ sudo mv /home/Myself/Documents /home/Dropbox/Documents
Step 3: Create a directory symbolic link at the original location to link to the folder which moved into Dropbox folder. Note that for Linux/Unix, the position of the source and target in the link command argument is the other way round.
$ ln -s /home/Dropbox/Documents /home/Myself/Documents
Note: The "-s" option is for softlink creation. Otherwise, the command will create a hardlink.
You are done.