After upgrading to a newer version of Netvisor, you can rollback to an earlier version and preserve the current configuration. The new configuration is applied before booting into the previous environment so that critical ACLs and security vFlows are present when Netvisor restarts.
A new parameter, apply-current-config, for the command, bootenv-active-and-reboot, provides support for this feature.
Before rebooting, Netvisor copies the current boot environment transaction logs into the target boot environment.
After rebooting, Netvisor performs the following:
Reads the copied transaction logs, and sorts all transactions by time, then scope, fabric>cluster>local, and then the transaction ID.
Parses the list of all transactions from oldest to newest.
If the current transaction ID for the scope is less, Netvisor rolls the transaction forward, and deletes the files when done.
Caution! Retaining the current configuration when booting to an older version of Netvisor is best-effort. Some transaction IDs from the newer (or current) version may not properly apply due to feature incompatibility. It is not guaranteed that all changes are applied.
Caution! You must apply the parameter, apply-current-config, on all nodes in the fabric. There is no coordination across the fabric for this process, therefore the commitment of fabric transactions on one node but not another using this process causes the fabric to go out of sync and may result in unrecoverable errors.