» Backwards Compatibility

» For 1.0.x

Vagrant 1.1+ provides full backwards compatibility for valid Vagrant 1.0.xVagrantfiles which do not use plugins. After installing Vagrant 1.1, your 1.0.xenvironments should continue working without modifications, and existing runningmachines will continue to be managed properly.

This compatibility layer will remain in Vagrant up to and including Vagrant 2.0.It may still exist after that, but Vagrant's compatibility promise is only fortwo versions. Seeing that major Vagrant releases take years to develop andrelease, it is safe to stick with your version 1.0.x Vagrantfile for thetime being.

If you use any Vagrant 1.0.x plugins, you must remove references to these fromyour Vagrantfile prior to upgrading. Vagrant 1.1+ introduces a new pluginformat that will protect against this sort of incompatibility from everhappening again.

» For 1.x

Backwards compatibility between 1.x is not promised, and Vagrantfilesyntax stability is not promised until 2.0 final. Any backwardsincompatibilities within 1.x will be clearly documented.

This is similar to how Vagrant 0.x was handled. In practice, Vagrant 0.xonly introduced a handful of backwards incompatibilities during the entiredevelopment cycle, but the possibility of backwards incompatibilitiesis made clear so people are not surprised.

Vagrant 2.0 final will have a stable Vagrantfile format that willremain backwards compatible, just as 1.0 is considered stable.