RSYNC

#!/bin/bash

sudo rsync -rltDvu --modify-window=1 --progress --delete --delete-excluded --exclude-from=/home/bob/Bash/BackupBigExclude.txt /home/bob/ /media/harddrive/backup

Explanation of commands: 

rsync: this is the program used to sync the data. Rsync basically can check the destination data and see if any changes have been made in the source data so that ONLY the source data that has been changed is updated. VERY useful.

-r: copies directories recursively

-l: copies symlinks as symlinks

-t: preserves modification times

-D: preserves device and special files

-v: shows output (verbose)

-u: skips files that are newer at the destination

--modify-window=1: this is essential if you are backing up to a filesystem that is NOT ext3 or ext2, e.g. NTFS or FAT32. Basically in windows filesystem times are kept as even numbers. This command tells rsync to ignore file changes that are only 1 second in difference from the original. It is almost impossible that you will create a file, sync it, and in ONE second make a change and want to sync it again. So it is safe to use this option and it means that rsync will not back up everything every time simply because of a one second change.

--progress: simply shows the progress

--delete: this is important. Basically rsync syncs files that have been changed. But what if you delete a file from the source directory? This command deletes it from your backed up hard drive as well.

--delete-excluded: this deletes folder/files that you have specifically excluded.

--exclude-from=/home/bob/Bash/BackupExclude.txt: this is the other crucial command. This basically tells rsync to exclude the files/folders found in the list BackupExlude.txt. To create this list do the following:

gedit /home/bob/Bash/BackupExclude.txt

Now in the text editor it is entirely up to you what you want to exlcude.

This is my list:

MyDownloads

.VirtualBox

lost+found