The sys admin’s daily grind: Unison

SYNCING IN UNISON

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Charly may be a traditionalist with sync-unfriendly duplicate home directories, but a little utility called Unison helps keep his data consistent . This month you’ll learn why Rsync sometimes isn’t enough.

I’m an old-fashioned kind of guy. You can tell by the way I still use a desktop computer, instead of entrusting my data to a laptop. The downside of this traditionalism is that I sometimes need to synchronize my home directories between my desktop and my laptop. Rsync is not a solution to this problem. The Rsync tool is a one-way street that updates a slave copy to reflect the master copy status. If I used Rsync consistently with the --delete parameter set, it would flatten any changes I had made on the slave machine in the meantime. The antidote to this problem is a tool called Unison.