To update a backup, just run the same backup script again.

Personal Backup optimizes backups by limiting their scope to copying only those files that were created and/or modified in the source since the last backup.
Backups will not copy again files that have not changed and already exist in the destination.

How do I set incremental backups?

----------------------------------------------------------------------------------------------------------------------------------------------
It is very important to distinguish between "updating a backup" and "synchronizing".
A SYNCHRONIZATION IS NOT A BACKUP.
MAKE SURE YOU REGULARLY BACK UP THE DATA YOU SYNCHRONIZE, _ESPECIALLY_ BEFORE THE FIRST SYNCHRONIZATION.
----------------------------------------------------------------------------------------------------------------------------------------------

• DIFFERENCES BETWEEN BACKUP AND SYNCHRONIZATION
Synchronization and backup are two very different operations.
It is ESSENTIAL to understand page 8 of the Personal Backup User Manual to become familiar with these two concepts.
This is very useful so you are not surprised by some of the results of this feature.
(See main risks at the end of this page).

In short:
* a BACKUP is a 'one-way' file copy (conservative action).
Files from a source are COPIED to a destination.
Whatever the situation is on the destination, this will have NO impact on the source.
* a SYNCHRONIZATION is a 'two-way' operation (a destructive action by default).
- This process CANNOT be undone and renders the contents of the source AND destination strictly identical by combining their respective files and folders. It adds the new files to the location where they are not found, AND removes deleted files in the location where they are found.
- While synchronizing for the first time, Personal Backup copies each file from the source to the destination AND copies each file from the destination to the source. The results are 2 identical folders from which Personal Backup builds an extensive listing with detailed characteristics of the files (name, location, size, modification date, etc.)
- After the first time you run a synchronization, each new synchronization tells Personal Backup to find and reproduce all changes of one location to the other one.
=> When you delete a file in one folder (either source or destination), it will systematically be erased on the other side (during the next synchronization) to ensure that both folders continue to have exactly the same files and folders.

• SYNCHRONIZATIONS CAN BE RISKY
Using the synchronization feature can be risky if used for backup purposes.
In general:
If you are not entirely sure to have understood exactly what Personal Backup's synchronization feature is designed for, use the backup feature.
In actual usage, Personal Backup's synchronization feature is justified only in very rare cases.
Even more, when its use is justified, the power of this feature is often under exploited.
If, after reading this article, you are still planning to use the synchronization feature, please describe to us what you want to accomplish, so we will confirm if the scenario you have imagined is the more adapted to your situation.
As sources and destinations are always kept strictly identical, if a folder is deleted in one side, it will be also be deleted on the other side during the next synchronization.
Since many users don't give enough attention to this fact, we insist that:
----------------------------------------------------------------------------------------------------------------------------------------------
A SYNCHRONIZATION IS NOT A BACKUP.
You should ALWAYS REGULARLY BACK UP ALL THE DATA THAT YOU SYNCHRONIZE, especially BEFORE THE FIRST SYNCHRONIZATION.
You should do this with both the source AND the destination, since synchronizations cannot be undone, and this two-way process combines the files of the two locations to make them identical.
----------------------------------------------------------------------------------------------------------------------------------------------

EXAMPLE: Synchronization which can lead to DATA LOSS
Step 1: You synchronize two folders.
Step 2: In the destination folder, you delete one or more folders, or you remove everything from it (either accidentally or intentionally).
Step 3: You run the same synchronization script that you ran in Step 1.
=> Personal Backup will analyse the contents of the source, the contents of the destination, and the state in of the source and destination the last time they were synchronized.
Personal Backup will detect that your last action was to remove folders from the destination.
The program will logically conclude that, to maintain your files synchronized, it should remove these deleted folders from the source.
If you wish that Personal Backup never deletes data while synchronizing, this is possible by checking the Synchronization Option "Never delete anything", but note that in this case, source and destination will no longer be identical. (This is the reason why this feature is disabled by default when you create a new synchronization script.)

Other risks of data loss:
- If the clock of your Macs have incorrect dates and/or times.
- If at least one of the volumes is Windows formatted and/or is a networked volume.
- If one of both disks are faulty and generate disk errors.

• Synchronization - For what is this feature designed for?

Typical use of the synchronization feature is while a sales person is on the road with a laptop and that a secretary has a copy of all its documents folder on a desktop at the office.
The sales person works on some documents on the laptop, the secretary also works on some documents on the desktop.

 At the end of the day, the synchronization will:
- Copy all documents created or modified on the laptop => to the secretary's desktop
AND
- Copy all documents created or modified on the desktop => to the sales person's laptop

Note: When a file have been modified on both sides (let's say that the last sync have been done yesterday and that today 11:00 the sales person have modified a document, and that at 15:00 the secretary has modified the exact same file; on next synchronization, Intego Backup will detect the conflict and will ask what you would like to do.

This default comportement can be modified in the Synchronization Options pane.