|Unison file synchronisation for modern computer nomands
||18 Nov 05
Do you know this scenario? Got some files on your laptop, some on your
desktop machine at home, some in the office, some on server X? If that is
the case, it’s high time you become an addicted Unison user. Unison
is pure firelsynchronisation for Unix and for windows.
It allows two replicas of a collection of files and directories to be
stored on different hosts (or different disks on the same host), modified
separately, and then brought up to date by propagating the changes in each
replica to the other.
Unison shares a number of features with tools such as configuration
management packages (CVS, PRCS, Subversion, BitKeeper, etc.), distributed
filesystems (Coda, etc.), uni-directional mirroring utilities (rsync,
etc.), and other synchronizers (Intellisync, Reconcile, etc). However,
there are several points where it differs:
- Unison runs on both Windows and many flavors of Unix (Solaris, Linux, OS X,
etc.) systems. Moreover, Unison works across platforms, allowing you to
synchronize a Windows laptop with a Unix server, for example.
- Unlike simple mirroring or backup utilities, Unison can deal with updates
to both replicas of a distributed directory structure. Updates that do not
conflict are propagated automatically. Conflicting updates are detected and
- Unlike a distributed filesystem, Unison is a user-level program: there is
no need to modify the kernel or to have superuser privileges on either
- Unison works between any pair of machines connected to the internet,
communicating over either a direct socket link or tunneling over an
encrypted ssh connection. It is careful with network bandwidth, and runs
well over slow links such as PPP connections. Transfers of small updates to
large files are optimized using a compression protocol similar to rsync.
- Unison is resilient to failure. It is careful to leave the replicas and its
own private structures in a sensible state at all times, even in case of
abnormal termination or communication failures.
- Unison has a clear and precise specification.
- Unison is free; full source code is available under the GNU Public License.