Apple Mac OS X Server (Administrator’s Guide) - Manual (Page 553)

Tools for Advanced Users 553
Understanding UNIX Command-Line Structure
UNIX commands share some basic conventions. First you enter the name of the tool, then
any information the tool needs to carry out your request. Most tools come with help or man
(short for “manual”) pages that describe how to use the tool. Help pages give an overview of
arguments (also known as options or parameters) that the tool understands. Man pages give
more detail and examples:
m To find help pages, type the name of the tool and then the argument “-help” (for example,
“dsimportexport -help”).
m To find man pages for a tool, type “man”, followed by the tool name (for example, “man
ssh”).
When you supply information in a command, enclose location or item names that include
spaces in quotation marks (“like this”).
Secure Shell (SSH) Command
Secure Shell (SSH) lets you send secure, encrypted commands over a network. With SSH
turned on, you can use the Terminal application to open an SSH session and use command-
line tools to securely configure a remote server. You can also connect a terminal to a headless
server through the serial port and log in using SSH.
For complete information about SSH, type “man ssh” in Terminal.
Enabling and Disabling SSH Access
Access to Mac OS X computers using SSH is enabled by default.
You can disable SSH access to a Mac OS X computer locally or remotely:
m When logged in locally to a Mac OS X computer, make sure that “Remote login” in the
Sharing pane is not selected.
m To disable SSH access to a remote server, while in an SSH session with the remote
computer, type “systemsetup -setremotelogin off ”.
You can reenable SSH access only locally.
Opening an SSH Session
Open an SSH session and log into a remote server when you manage the remote server
using command-line tools.
To open an SSH session and log in to the server:
1 Open Terminal.