Ceph

$ bin/ceph mds 
no valid command found; 10 closest matches:
mds tell <who> <args> [<args>...]
mds compat show
mds stop <role>
mds deactivate <role>
mds set_max_mds <int[0-]>
mds set max_mds|max_file_size|inline_data|allow_new_snaps|allow_multimds|allow_multimds_snaps|allow_dirfrags <val> {--yes-i-really-mean-it}
mds fail <role_or_gid>
mds repaired <role>
mds rm <int[0-]>
mds cluster_down
Error EINVAL: invalid command

e.g. "mds deactivate" is flagged obsolete. (Attempting to run it gives an proper ENOTSUPP error.)