is an open-source file synchronization tool which allows bidirectional file sync between a pair of replicas located on the same host, as well as on different hosts. Unison detects (non-conflicting) updates in either replica, and automatically applies them to the other replica, so that both replicas remain in sync. Conflicting changes are also detected, and displayed for manual intervention. File sync over networks can be done either via a TCP socket connection or over a secure SSH connection. The Linux version of Unison is available as two flavors: a command line interface (CLI) client and GTK+ based GUI tool.