[Pacemaker] stonith_admin --metadata --agent fence_pcmk " output "Command failed: Invalid argument

[bin chen]

Hi ,all,
I use stonith_admin --list-installed to check how many fence_agents :
 fence_pcmk
 fence_legacy
 fence_fronware
The I want check the metadata of fence_pcmk to find out the parameters
associated with the fence device:
stonith_admin --metadata --agent fence_pcmk
Command failed: Invalid argument
I run the commond with fence_legacy,fence_fronware ,I get the same output.
why?Any help will be appreciate.
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