Linux Synchronization – Real-Time File Synchronization Methods

You want bi-directional sync. Take a look at unison, which does this: http://www.cis.upenn.edu/~bcpierce/unison/

For example, on Debian/Ubuntu:

$ sudo apt-get install unison
$ unison MAC/ LINUX/

If you have trouble with permissions (example ext4 -> FAT):

$ unison -perms 0 vlc-2.2.0/ /media/sf_vlc/vlc
Contacting server...
Looking for changes
Reconciling changes

vlc-2.2.0      vlc                
new dir  ---->            /  [f] 

Proceed with propagating updates? [] y
Propagating updates

You could probably hack this together using inotify and more specifically incron to get notifications of file system events and trigger a backup.

Meanwhile, in order to find a more specific solution you might try to better define your problem.

• If your problem is backup, it might be good to use a tool that is made to create snapshots of file systems, either through rsnap or a snapshoting file system like xfs or using any file system with lvm.
• If your problem is sycronizing, perhaps you should look into distributed and/or netowrk file systems.

Edit: In light of your update, I think you are making this way to complicated. Just make a folder in your dropbox for scripts. Then in your bashrc files do something like this:

export PATH=$PATH:~/Dropbox/bin
source ~/Dropbox/bashrc

Whatever scripts you have can be run right from the dropbox folder in your home directory, and any aliases and such you want synced can go in a file inside Dropbox that gets sourced by your shell.

If other people besides you need access to the scripts, you could symlink them from your Dropbox to somewhere like /usr/local/bin.