incremental backup tool that can handle interruptions?

Question

Is there a recommended incremental backup tool that can handle interruptions such as the external USB disk being disconnected in the middle of an update?

Answer 1

Rsync / Grsync

The command line file transfer utility Rsync and its GUI Grsync is designed for file transfers via a network connection but can also nicely used for local backup purposes. Due to its provenience from networking it is capable of performing backups with a resume option by using the option --partial or -P:

--partial By default, rsync will delete any partially transferred file if the transfer is interrupted. In some circumstances it is more desirable to keep partially transferred files. Using the --partial option tells rsync to keep the partial file which should make a subsequent transfer of the rest of the file much faster ^{Manpage rsync}

We are also able to define a directory where rsync will store partially transferred files until transfer was complete with the option --partial-dir=<DIR>.

An example command for a partial incremental upgrade would be something like:

rsync -auxP <source> <destination>

But: by all means do not unplug an external USB drive while running a backup as this puts the integrity of your whole filesystem at risk. Do not trust a backup on a temporarily unplugged drive!

Answer 2

I think your best bet is a mix of rsync and sharing the USB device over the network and using rsync to copy the folders. rsync will handle the file level stuff and the network layer means windows will handle the disconnection of the USB drive and in turn shut down the share which means rsync will fail. Or at least as far as I can tell.

Otherwise I think you should start looking at cloud based disk storage as a more complete out of the box solution.