CHAPTER 1

The Computer Centre maintains a variety of UNIX computers which support the academic and research activities in the University. These include a High Performance PC Cluster for compute-intensive applications, general purpose and other special purpose host computers.  There are also clusters of UNIX workstations for connecting to the central servers. These systems are all connected to the campus network so users can access the various servers through the networked PC's.

Details of these host computers are printed at http://www.itservices.hku.hk/home/facilities/host.htm

All these host systems run the UNIX operating system.  However, each version may be slightly different e.g. Solaris for SUN, AIX for IBM, HP-UX for HP, and Red-Hat Linux,  but unless otherwise specified, the discussions below apply generally to all versions of the Unix system.

1.1 Getting a User Account

In order to use any of the UNIX facilities provided by the Computer Centre, you need a UNIX computer account. For how to apply for a Unix account, see http://www.itservices.hku.hk/handbook/csh/chap6.htm#6.1.1

1.2 Login and Logout a Unix System

You must login the UNIX system by providing the correct user account name and password before you can issue any system commands, develop or run programs, or use any of the applications or services provided on a central UNIX system.

You can login a UNIX system using a Telnet session. Enter your login name and hit the return key. The UNIX system will also ask for your password. Enter your password and hit the return key. The password will not be shown on the screen so as to maintain privacy.  If the login is successful, then the UNIX session will be under the control of a start-up program which is normally the C shell. The login C shell prompt is set to the nodename of the system e.g. 'hkusua'.

Note: The following examples make use of the HKUSUA or HKUCC systems for illustration, other UNIX workstations are similar.

A sample log of a successful login on the HKUSUA system is shown below :-

UNIX(r) System V Release 4.0 (hkusua)

login: h0012345 <enter>

Password: <enter>          - password typed in is not echoed

Last login : Tue Jul 11 10:10:30 HKT 2000

hkusua% _                  - HKUSUA Login shell prompt

C Shell                 Bourne/Korn Shell

% logout  <enter>  or

% exit  <enter>

You can connect from one host system to another host system on the HKU Campus Network, the HARNET or the Internet by using the Telnet command. For example, you can connect to the HKUSUA system from the HKUCC system with the following command:

$ telnet hkusua <enter>

or

$ telnet hkusua.hku.hk <enter>

UNIX(r) System V Release 4.0 (hkusua)

login: _

If your login name and password are entered correctly at this prompt, you will be connected to the HKUSUA system from HKUCC.

1.2.2 Rlogin Sessions with Remote Hosts

You can also use the rlogin command to establish an interactive session to a UNIX system from another computer that supports the rlogin command. However, the usage of rlogin is not recommended for general users and the Centre's UNIX servers are configured not to offer this service by default. For illustration, you can login System A from System B by using the rlogin command, as follows:

b%  rlogin a <enter>

    SYSTEM MESSAGE OF SYSTEM A

    . . .

a%  _

There are cases where you do not have to enter your account password again as some systems share the same password file.

1.2.3 Telnet Session from a Microsoft Window

The most popular way to establish a telnet session is by using the Telnet program in the MS Window environment.  If you are working within the university campus, you can find one of the following icons in the Computer Centre Programs Group:

Double click the "Telnet" icon to invoke the telnet program. Type ALT-D to select a server.

Choose the HKUSUA system and click "Connect".  You will be asked to enter your username and password to login the HKUSUA system.

If you are working outside the university campus, and do not have the above Telnet icons, you can use the telnet program in your Windows operating system.   Click the "Start" button in Windows, choose "Run" and then type "telnet hkucc.hku.hk" or "telnet hkusua.hku.hk" to make the connection.