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# Upgrading configs

Occasionally, changes are made to Butane configuration specifications that break backward compatibility or add new functionality. While this is not a concern for running machines, since Ignition only runs one time during first boot, it is a concern for those who maintain configuration files.

For details about changes in new versions of Butane config specs, see the guide for your specific config variant:

- [Fedora CoreOS](upgrading-fcos.md) (`fcos`)
- [Flatcar](upgrading-flatcar.md) (`flatcar`)
- [OpenShift](upgrading-openshift.md) (`openshift`)
- [RHEL for Edge](upgrading-r4e.md) (`r4e`)
