Why i cant execute a linux command through asterisk manager?

dear all, i want execute a linux command through asterisk manager, but failed. in asterisk CLI ,i can excute a linux command by “!” .why this useage can excute by asterisk manager?

Asterisk CLI has specific commands for the Asterisk program.
I am sorry I do not have the direct link. A list is located at voip-info.org.
Its another very helpful web site for all types of voip info.
Linux commands are simular in some ways. To use Linux commands
I have to be logged into my “root” or Admin, if you will,
to execute Linux Commands. Asterisk CLI will give you info and assist
in implementing changes such as a “reload” after a change has been made
in extensions.conf or checking the sip registry such as "sip show registry"
and so on.

Hope this helps !