Dec 03, 2019

Overview

When deciding if an existing (backup) copy of a file needs an update, the program looks at the triplet of "created" timestamp, "last-modified" timestamp and the file size. If one or more of these is different between the source and backup copies, the file is deemed modified and it is scheduled for an update.

Taking over an existing backup

"Created" timestamps are handled in special way on the very first run of a new backup job.

If a backup copy already exists and it only differs in "created" timestamp, then the program will merely reset this timestamp to match that of the source AND will skip re-copying of the file.

This is done to accommodate the case of taking over an existing backup  created with conventional copying tools, like copy-pasting in Windows Explorer, through the "copy" command, etc. These tools preserve "last-modified" time, but set "created" timestamp to the time of copying.

Once the backup completes, the default is restored and the app starts paying attention to "created" timestamp again. That is, if it changes, the file is deemed modified.

Override - Don't compare, but copy

The program can be configured to ignore "created" timestamps when checking if a file has changed and needs updating.

This is done by adding the following override to the backup settings:

        conf.ctime_match  1

A difference in "created" time won't trigger an update, but it _will_ be copied if a file is updated for another reason.

Override - Don't compare, don't copy

It is also possible to suppress the copying of "created" timestamps.

When this option is enabled, the program will preserve backup's copy original "created" timestamp and copy over only the modification timestamp.

This is done by adding the following override to the backup settings:

        conf.copy_extras    attributes

which overrides the default of "ctime, atime, attributes".

Suppressing "created" timestamp copying automatically suppresses their use for file change detection (as per above).

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See https://bvckup2.com/support/forum/topic/1140 for how to add an override.