If an new target filesystem is not formatted with "mkfs.lustre --replace" for some reason (e.g. existing scripts/framework to format the filesystem), then it would be useful to have a "tunefs.lustre --replace" option to reset the OST config, label, etc. so that it can be re-added to the filesystem without trying to register with the MGS again. Otherwise, the OST will try to re-register with the MGS because LDD_F_VIRGIN is set at mount time and fail.

It looks like this is almost possible with the existing code, but if it is then it isn't documented in tunefs.lustre.8 man page.