Forces a node to save the nodes.conf configuration on disk. Before to return the command calls fsync(2) in order to make sure the configuration is flushed on the computer disk.

This command is mainly used in the event a nodes.conf node state file gets lost / deleted for some reason, and we want to generate it again from scratch. It can also be useful in case of mundane alterations of a node cluster configuration via the CLUSTER command in order to ensure the new configuration is persisted on disk, however all the commands should normally be able to auto schedule to persist the configuration on disk when it is important to do so for the correctness of the system in the event of a restart.

@return

@simple-string-reply: OK or an error if the operation fails.