Be sure that any terminal emulation software settings that add characters to keyboard input are OFF. If the virtual printer server sees any invisible characters, such as line feeds, after the user name or password, access is denied.
It is important that the terminal emulation software does not send characters other than the required username of 'su', and privileged password of 'system'; any characters are acceptible as a username, whether valid or not, but if EITHER OR BOTH fields are incorrect, access is denied after entering the password.
Sample Session
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username> su
Server> su
password> system
Server>>
Once the 'Server>>' prompt appears, you are logged into supervisor access.
Other Help
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Online help is also available to assist you. For example, 'show services' displays the current services. amd 'help show services' displays all the arguments to 'show services' and what they do.