[chef] To run chef-client on specific nodes

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Hi,

I have multiple nodes registered with chef-server . I want to run 
"chef-client"
on some nodes . I checked on internet i found i can use "roles" by creating
roles and assigned roles to servers.

But without creating roles can i do this ?

My Scenario : I have following nodes 

a) abc.com
b) def.com
c) ghi.com
d) jkl.com

** can i execute "knife ssh " "  chef-client" only on def.com and jkl.com
nodes.

When i execute "knife ssh "name:*" chef-client , it will run on all nodes 
which
are registered with chef-server.

Please let me know your suggestions or recommendations if any . Appreciate 
your
feedback and Input .

Thanks in Advance !!

Regards,
Mittal.A