What are the different shells available in Data ONTAP 8 cluster mode and what are their uses?

There are 3 different shells available within Data ONTAP 8 cluster mode operating system.

clustershell
This is the default shell that is started when a user logs into the system. This shell was called NG shell and could be started by running 'ngsh' from BSD prompt of the system.

nodeshell
This is the shell that can be started by running the command 'system node run'. Commands can be run in node shell from clustershell by using the following syntax : 'node run <nodename> <command>'.
Node shell for any node in the cluster can be accessed from any other node. Nodeshell was known as dblade in Data ONTAP GX.

Systemshell
This is the low level shell used for advanced, diagnostic and troubleshooting purposes. Under normal circumstances systemshell should not be used without directions from NetApp Support. Systemshell is specific to a node. You may access a remote system which is in the cluster from a different node by specifying the node name. Systemshell was known as BSD shell in Data ONTAP GX and was started when root logged into the node. In order to unlock the systemshell for the diag user.