Because of how the arguments to mkfs/tunefs are parsed, these commands are sensitive to the order of arguments. Ideally, --key=value parameters should not be order sensitive. At least, these ordering rules should be documented.

--erase-params

Fails silently if erase-params is not after any param arguments.

This is OK:

tunefs.lustre --erase-params --mgsnode=<new_nid(s)> --writeconf /dev/..

But if we do this, it does not work properly (erase-params deletes the previous mgsnode argument):

tunefs.lustre --mgsnode=<new_nid(s)> --writeconf --erase-params /dev/..

--index

Fails with "--index only valid for MDT,OST" if --index does not come after the target type argument.

This is OK:

tunefs --mdt --index=0

This is not OK:

tunefs --index=0 --mdt