The Databar System at DTU - G-Bar Wiki - DTU

The Databar System at DTU
September 2010
1

Authors: Henrik Madsen, Bernd Dammann, Mark Gjøl, Povl Ole
Haarlev Olsen, Jørn Villesen Christensen, Karen Markvard Martensen,
Christian Theede, Christian Thode Larsen, Jakob Rosenkrantz
de Lasson and Anders la Cour Bentzon.
With contributions from Joakim C. Allerup.
Translated from Danish by Joy Sue Christensen.
This document was typeset with LATEX.
Version: August 31, 2010 23:01
3

4 The Databar System at DTU
Contents
1 Introduction 5
2 Databar system 5
2.1 The physical databars . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.2 Use of mobile devices . . . . . . . . . . . . . . . . . . . . . . . . . 5
3 DTU Portal and CampusNet 7
4 Support and helpdesk 7
5 ThinLinc remote login 8
6 The G-Bar 9
6.1 Login and logout . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
6.2 User interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
6.3 Browsers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
6.4 E-mail and e-mail clients . . . . . . . . . . . . . . . . . . . . . . . 13
6.5 UNIX and the file system . . . . . . . . . . . . . . . . . . . . . . . 14
6.6 G-Bar software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
6.7 Printers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
6.8 Network commands . . . . . . . . . . . . . . . . . . . . . . . . . 21
6.9 Job processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
7 The Winbar 26
7.1 Documents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
7.2 Installation of software in the Winbar . . . . . . . . . . . . . . . 26
7.3 Formatting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
7.4 Printers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
7.5 Scanners . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
7.6 UNIX from Winbar . . . . . . . . . . . . . . . . . . . . . . . . . . 27
8 Linux 28
8.1 Linux programs . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
8.2 DTU-LUG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
9 Mac at DTU 29
9.1 MacVærk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

2 Databar system 5
1 Introduction
The purpose of this guide is to introduce new users to the databar system
at DTU and provide basic information about the G-Databar 1 and the Winbar.
Furthermore, Section 3 describes the university portal (intranet) and Campusnet
(the information center which covers the DTU curriculum). To keep all
this information compact and overseeable for you, many instances below refer
to further details available at the G-Bar web site: http://www.gbar.dtu.dk
and at the Winbar web site: http://www.winbar.dtu.dk. An overview of the
databars at DTU can be found at http://www.databar.dtu.dk.
2 Databar system
The objectives of the databar system at DTU are to make the full range of applications
and computer power available to students and researchers regarding
the curriculum, writing and computing needs in connection with research,
work projects, and other study activities.
2.1 The physical databars
The DTU databar system consists of a number of databars spread on the DTU
area, see table 1 on the following page. The map on the last page of this guide
shows the location of these databars. Terminals and printers can be accessed
from the databars, and since all of the databars are connected within the same
system, it is possible to access one’s own files at any of them.
All databars must conform with certain requirements of the network program
and software which makes it possible to connect the databars, and which
ensures that at least the minimum of software is accessible everywhere.
In the UNIX and Linux databars, you have the possibility to connect to
a Windows Desktop (Remote Desktop) 2 . Similarily, you can start a UNIX or
Linux desktop in the Windows databars (ThinLinc).
2.2 Use of mobile devices
Provided that you have a wireless network adaptor in your mobile computer,
you can use your own mobile device as a thin client 3 (the UNIX system). After
1 G-Databar is also called G-Bar
2 For more information, go to http://www.gbar.dtu.dk/wiki/Windows_FAQ
3 The thin clients are the terminals that are available for use in the G-Bar and in some of the
other databars. See table 1.

6 The Databar System at DTU
Databar Building Type of databar Number of workstations
B-Bar 116 Windows databar 135
Diplom E- and IT-Bar 308 Winbar 45
325 Winbar 84
E-Bar 341 Winbar/Linux 64
325 48
G-Bar 302 UNIX / Linux 34
(SunRay terminals) 303N UNIX / Linux 96
303S UNIX / Linux 11
305 UNIX / Linux 30
306 UNIX / Linux 64
308 UNIX / Linux 72
K-Bar 208 Winbar 27
208 UNIX 22
210 Winbar 60
M-Bar 402 Windows databar 24
414 Windows databar 40
421 Windows databar 53
VR-Bar 305 Windows 25
101-Databar 101 Winbar 64
Table 1: Buildings with databar workstations
installing a ThinLinc client (described in Section 5 on page 8) you can use your
mobile device just like any other thin client on campus.
To access the internet and computing servers in the G-Bar through the wireless
net, we recommend that you use Eduroam. The Eduroam-net is the free,
wireless network of the universities for the students and the employees. With
Eduroam you will also be able to access the wireless net of other universities
in Denmark and abroad. However, the configuration of Eduroam depends on
operating system (Windows, Linux, MacOS), and you may have to install a
program in order to access the wireless network with Eduroam. For more information
on Eduroam, please consult the G-Bar wiki (http://www.gbar.dtu.
dk/wiki/Eduroam).
Alternatively, you can use the net called “DTU”. In order to authenticate,
you will need to enter your credentials every time you log on to this wireless
network, which is quite cumbersome. “DTU” is also not encrypted, which
means that people could potentially eavesdrop on your communication. For

4 Support and helpdesk 7
these reasons, we recommend using Eduroam instead.
3 DTU Portal and CampusNet
DTU’s web portal at http://portalen.dtu.dk/ provides an index of the information
that is available to all DTU students and employees. There you can
also read campus news, confirm which courses you are registered for, discover
information groups, and find other useful notes and tips. The portal functions
as a frontpage for CampusNet, too.
CampusNet gives you access to numerous study-related functions and data.
For example, this is where you register for courses or cancel a course registration.
You can locate other students here, and often you will find discussion
groups related to particular courses. It is also possible to access your student
e-mail and download free software at CampusNet.
If you want to go directly to CampusNet without going through the portal,
you can use this web address: http://www.campusnet.dtu.dk/, or even
shorter: http://cn.dtu.dk.
4 Support and helpdesk
If you need technical support with any of the IT systems at DTU, you may
write to itsupport@student.dtu.dk. This is a generic e-mail address, and the
supporters will take care of forwarding your request to the right people — no
matter if your question is about the Winbar, the G-Bar, the K-Bar etc. Please
be as specific as possible with your support question; the more details you
provide up front, the less the supporters will have to ask you afterwards, and
the faster your problem can be solved.
Alternatively, you may visit the G-Bar support office, which is located in
building 308, room 119 (phone number 51265). They help with G-Bar issues,
including problems that you might have connecting to DTU from a mobile
device or home computer. They can also help out if you have trouble installing
course-specific software on Linux or Windows computers. The opening hours
can be seen at http://www.gbar.dtu.dk.
If you have forgotten your password, you will have to have to visit the
student office in building 101 with a valid ID in order to get a new one.

8 The Databar System at DTU
5 ThinLinc remote login
It is possible to log in to the G-Bar from your home or through the DTU Wireless
Network. Sitting at your computer anywhere, you can make use of the
G-Bar computing power as well as the large selection of programs. For this
purpose, the G-Bar recommends and supports the product ThinLinc offered
by Cendio A/B.
ThinLinc is a client that combines technologies such as SSH and VNC to
support remote graphical login. For those who might not fully understand
what this is, it means that a “window” appears in your computer which starts
a terminal session just as if you were working at a G-Bar terminal.
The ThinLinc client can be downloaded freely at http://www.gbar.dtu.dk/
software for use with Linux, Mac, or Windows.
When the installation is complete, the program starts with the command
tlclient on a Linux terminal or by clicking on the ThinLinc icon in Windows.
The program should bring up the following screen where you then enter your
own server address, username, and password.
• Server: thinlinc.gbar.dtu.dk
Figure 1: Thinlinc client login
• Name: your student account number
• Password: your DTU password
After that you are ready to connect, and you do that by clicking on the
button Login. Now you select a user interface the same way as in the G-Bar,
and you are online.

6 The G-Bar 9
Some very useful functions of ThinLinc are the audio support and support
for the printer connected to the end point where the client is operating, for
example your home computer. You can find more information about setting
up a ThinLinc client on the G-Bar homepage.
It is also possible to log on to the G-Bar from the Winbar machines, which
also offer access through ThinLinc.
6 The G-Bar
The G-Bar architecture at DTU is an up-to-date UNIX-based (Solaris, Linux)
computer system. There is a cluster of central computing servers in the G-Bar,
that are connected to a pool of SunRay servers (grayNN). The SunRay-servers
make access to all the many SunRay terminals in the G-Bar system possible, so
do NOT ever start a program on this server.
Connected with the G-Bar are also a number of computers which are reserved
for users categorized as the HPC group (High Performance Computing).
For details on that access and use, go to http://www.hpc.dtu.dk/.
6.1 Login and logout
6.1.1 Login
To log in to the G-Bar, you first key in your username (sometimes also called
your login or user ID). Typically, it is your student number in this form:
s001234. After keying in your username and pressing the enter key, the system
will ask for your password.
Note: When you key in your password, nothing shows in the password
box — Not even a line of asterisks (*). This is a security feature which prevents
anyone standing near you from seeing how long your password is.
Once you have entered your password and you have clicked on ok, you are
logged in.
The databars at DTU are all connected, so you have the same username and
password at all databars. Unless explicitly specified otherwise, that password
is meant, whenever such is required.
If you have a smart card, you can log in just by inserting the card. You
can purchase a smart card at the IMM Information Desk in Building 321 for 40
Danish kroner. For more information about smart cards, see the G-Bar website.

10 The Databar System at DTU
6.1.2 Graphical user interface
What you see when you have logged in to the system is a graphical user interface
(GUI). The default GUI is IceWM. If you prefer to use a different graphical
user interface, you can make that selection when logging in. To do so, click on
“Options” → “Session” in the login screen. However, IceWM is the recommended
GUI.
In the various graphical user interfaces, most programs can be started from
the central menu (see Section 6.2 on the facing page).
Unix terminals UNIX terminals give you command oriented use of the system.
Many users prefer this because after a bit of practice they have faster
and more effective use of the system when accessing it this way. Furthermore,
some commands and programs can only be accessed through a terminal. Terminals
can be opened from the central menu.
6.1.3 Changing your password
To change your password, open a terminal and write passwd:
hald(s001234) $ passwd
First you are informed of the criteria which your new password must meet to
be accepted by the system. The system will ask for your current password to
be sure that you are changing the password yourself.
When you have keyed in your password, the system asks you to repeat
your new password two times.
Since the password change has to be transmitted to numerous other computers,
it can take up to 3 minutes for the change to be valid everywhere in the
G-Bar.
It is recommended most strongly to change your password the first time you log in
to the databar system!
6.1.4 Logout
When you are finished using the system, you have to log out. Do this by clicking
on the menu button Logout. If you are using a smart card, you are “logged
out” as soon as you remove the card.
Before you log out, it is important that you shut down large programs such
as internet browsers, e-mail programs, OpenOffice, Maple, Matlab and Splus.
If you do not close the programs you used before logging out, you will keep
the system resources and licenses occupied unnecessarily.

6 The G-Bar 11
6.2 User interfaces
To use UNIX terminals is the most efficient way to work, but many prefer the
graphical display because work is more intuitive with visual access.
6.2.1 Central menu
There is a common menu that opens all G-Bar graphical environments, and it
is maintained centrally. That menu can typically be activated by a click of the
middle or the right mouse button on the background of the display. Most of
the programs installed on the G-Bar can be started from this menu. When a
program is activated from the central menu, it will be processed by the server
which is running with the lightest load at that moment.
6.2.2 File browser
The G-Bar offers a multi-tasking file manager (file browser), called XFE. You
can either start XFE in a terminal with the command xfe or in the menu under
“Desktop Environment”. For more information, see the G-Bar homepage.
6.2.3 IceWM
The graphical environment (or window manager) recommended for use on the
G-Bar is IceWM (see Fig. 2). This window manager looks and works somewhat
like Microsoft Windows. Just like Microsoft Windows, the menu opens with a
click on a menu bar at the bottom left corner of the display.
Figure 2: IceWM

12 The Databar System at DTU
Windows With IceWM you can ’drag-and-drop’ windows like the desktop
environment of Microsoft Windows. Place the cursor on the menu bar at the
top of the window, then click the left mouse button and hold it down while
you move the window to a new position. The window size can be changed by
clicking on any side of the window and drawing it in or outward.
IceWM windows have the same three buttons that Microsoft windows have
on the right side of the top menu bar. Also here, the outer right button closes
the window, the button in the middle maximizes it, and the left button of these
three minimizes the window. On the left side of the IceWM top menu bar there
is another button. Clicking on this one gives you a menu of things you can do
with the window. You can bring up the same list with a rightclick on any
empty space in the top bar. To close an IceWM window, you doubleclick on
the button at the left of the top menu bar.
IceWM offers several functions that Windows does not have. Unlike in
Microsoft Windows, it is possible to roll the window up so that only the top
menu bar remains visible, and the window’s position can be adjusted with
respect to other open windows on the desktop. With IceWM a window can
also be moved to another desktop. You can do that with the command Move
to in the window menu (left button on the top bar).
You can get a list of open windows by clicking on the background with the
middle button of the mouse. The list differentiates between the desktops you
are currently using.
Desktops IceWM gives you four desktops by default. This allows you to
prioritize and group the windows that you have open. For example, you can
have a browser open on one desktop and process the information on another
desktop. You switch between them by clicking on one of the four numbers on
the menu bar.
Themes If you do not like the standard wallpaper on IceWM, you can easily
replace it with any of a number of other possibilities. These are found at the
bottom of the start menu under “Settings” → “Themes”. If you are a staunch
user of Microsoft Windows, you might want to choose the XP theme .
6.3 Browsers
A good many internet browsers are available in the G-Bar. The graphical
browsers 4 that are available are Mozilla Firefox and Opera. They can be ac-
4 G-Bar also offers text-based browsers, which only run in terminals. These browsers do
not support graphical content so they only show text and no images. Some of them are lynx,
w3m, and links, each of which excels in a different way.

6 The G-Bar 13
tivated with the respective commands firefox or opera in the terminal, or
under “Internet” → “Browsers” in the menu. Firefox, as the standard browser,
can be activated via “Internet” → “Default Browser” in the menu.
6.4 E-mail and e-mail clients
Any employee or student at DTU have a personal e-mail adress, and for the
students the e-mail adress is sXXXXXX@student.dtu.dk, where sXXXXXX is
the student’s student number. It is important to check the e-mail regularly,
as the teachers and the administration at DTU often send out messages on
CampusNet or directly to the students’ e-mail adresses.
The student has a number of different options to access the e-mail. By logging
into CampusNet and clicking on “Webmail” in the topbar the e-mail can
be used directly in an internet browser. It is possible to read new e-mails,
answer or forward e-mails, write new e-mails, archive e-mails into different
folders etc.
By logging in on a terminal in the G-Bar the student is able to use the email
from one of the installed mail clients. Currently, Mozilla Thunderbird
is the standard graphical mail client. It is the default setup for logging into
your e-mail, so to access the e-mail all you have to do is key in your password.
The client can be started either from a terminal, writing the command
thunderbird, or from the menu, under “Internet” → “Mail clients” → “Thunderbird”.
Unless you change your default, Thunderbird can also be activated
in the menu under “Internet” → “Default Mail Client”.
The G-Bar has several text-based mail programs, of which pine can be recommended.
You can start it from the menu, navigating under “Internet” →
“Mail clients” → “Pine”, or you can write the command pine in a terminal:
hald(s001234) $ pine
The first time that you start pine, you will be greeted by a welcome screen. Use
the command Enter to proceed to the main menu. Pine can only be navigated
with the arrow and shortcut keys. The shortcuts that you can use are shown
at the bottom of the terminal screen. The symbol ^ before the shortcut tells
you that you must hold the ctrl key in addition to the shortcut combination
of keys.
Finally, it is possible to use the e-mail from your own computer. The e-mail
may be used with either the POP or the IMAP protocool.
See http://www.gbar.dtu.dk/ for details about the configuration.

14 The Databar System at DTU
6.4.1 Automatic forwarding of e-mail
You can forward your mail to another mail account. If you wish to do so, make
a file called .qmail in the home directory. You can do this using for example
the text editor NEdit:
hald(s001234) $ nedit .qmail
In the text editor you write:
&emailaddress@gmail.com
./Maildir/
where emailaddress@gmail.com is the address where your e-mail will be sent.
The line that reads ./Maildir/ orders the mail to be saved locally (otherwise
it is only forwarded).
6.5 UNIX and the file system
6.5.1 File system structure
The UNIX file system is structured like a decision tree with nested folders. 5
This is in principle the same as in DOS and Windows.
Figure 3: The tree structure of the file system
Each folder may contain a good many documents (files) and, if you wish,
also nested folders (sub-directories) on a deeper level, which again can contain
5 A folder is also called a directory, catalog, gallery, or in Danish, “mappe”.

6 The G-Bar 15
documents and even more nested folders. The structures may, for example,
look something like the sketch in Figure 3 on the facing page, which shows
how a user (here s001234) might have his or her home folder placed in the
global structure of the databar system.
Immediately after logging in, you will be in your own home folder, which
is named according to your individual User ID. The user has write access to
his or her own home folder, and thus can place documents and other folders
in it.
In Figure 3 on the preceding page you see an example where the user
s001234 has placed two documents (dok1 and dok2) in the home folder plus
one folder (bib.no.1/), and that folder contains two more documents (brev
and gml.brev).
6.5.2 UNIX commands
As mentioned before, in UNIX your work on a project can be either graphic or
command oriented. The big advantage of the command oriented use is that it is
much faster as soon as you get some practice in it. UNIX commands are keyed
in at a terminal window (see the section 6.1.2).
UNIX commands are generally written in the following syntax:
command 〈parameter〉 〈filename(s)〉
where the parameter “filename(s)” could also be “foldername”. File names can
include one or more joker characters or wild cards. Two joker characters that are
good to know are * which can stand for any other character or any sequence of
characters, and ? which can stand for a single character (note that the words
“document” and “file” mean the same thing. Sometimes we denote them as
documents, and sometimes as files.)
An example of the ls-command for listing files is
hald(s001234) $ ls -F *tex
which produces a list of all files in a folder the names of which end ‘tex’. The
parameter ‘-F’ means that you want to see the file type included in the list.
Note: Even if UNIX is very flexible with respect to file and folder names, you
should avoid using blank spaces, slashes (/) and other special characters in
your file and folder names.
The most important UNIX commands You can go a long way in command
oriented UNIX if you know the commands listed in table 2. These commands

16 The Databar System at DTU
Command Brief description
ls list contents of a folder
less, more, view show contents of a file
cd change folder
pwd show current folder
cp copy files (documents)
rm remove documents
mv move and rename documents
mkdir/rmdir make/delete a subdirectory
xpp, lp, lpr print document
man, info show manual/info for a command
gfile show file type
emacs advanced (and good) editor
nedit easy to use (graphic) editor
vi, vim the original unix editor
exit end terminal session
Table 2: The most important UNIX commands
are briefly explained in the following. For further information, write the man
〈command〉.
Contents of documents and folders The (ASCII) contents of a document
can, for example, be shown in a terminal window with the help of the command
less followed by the document name, as for example:
hald(s001234) $ less doc1
If the document fills more than one screen, the command less will show you
the first page only. You press the key ‘q’ to leave the less command. There
are other, and often better, commands you can use to view the contents of a
document – see Table 2.
A list with the contents of a folder can be produced on the screen with the
command ls. If you want more information than just the names of documents
and directories (files and folders), use for example the command ls -l (the
parameter -l gives you a more detailed list):
hald(s001234) $ ls -l
If the situation is as sketched in Figure 3 you will get something that looks like
the following:

6 The G-Bar 17
drwxr-xr-x 3 s001234 s00 512 Aug 8 13:23 .
drwxr-xr-x 3 s001234 s00 512 Aug 8 13:22 ..
drwxr-xr-x 2 s001234 s00 512 Aug 8 13:22 bib.no.1
-rw-r--r-- 1 s001234 s00 10 Aug 8 13:13 dok1
-rw-r--r-- 1 s001234 s00 257 Aug 8 13:23 dok2
We are not going into a full explanation of all this data. But it can be said that
the first character on the line might be ‘d’ (meaning a folder) or a ‘-’ (meaning a
file). The line also refers to information about the read (r) and write (w) access,
owner, group, document size, and the date and time at which it was last used.
Switch between folders Switching from one folder to another is done
with the command cd (change directory), and for example,
hald(s001234) $ cd dir.no.1
will take you down to the lower folder dir.no.1. The command
hald(s001234) $ cd ..
brings you back up again – Or generally one level up in the tree structure. In
the end, the command
hald(s001234) $ cd
will always take you back to the home folder.
It is also useful to know what ∼ does. If you use the command
hald(s001234) $ cd ~s001233
you will change to the user s001233’s home folder. That is possible, if you have
an execute right to that folder. If you also want to see contents of that folder,
you must have the read access.
Note that you can use “/” to start the path down from the root folder (top
of the tree), where otherwise the path is relative to the folder you are currently
working in. With the help of the command pwd (print working directory), you
can always find out which folder you are in.
Copy, delete, and move documents You can copy a document with the
command cp (copy) followed by the old and the new names, as shown here.
That is,
hald(s001234) $ cp old.letter new.letter
will establish a new document with the name new.letter, and it will be exactly
like the old.letter. The command can also be used to copy several documents
at once. In that case the “new name” is not a file name, but a new folder name
instead. If you are in the sub-directory (folder) dir.no.1, the command

18 The Databar System at DTU
hald(s001234) $ cp ../doc* .
copies the files doc1 and doc2 down to dir.no.1. Note that ‘..’ denotes the
folder that is just one level above the current folder, and ‘.’ denotes the folder
you are currently in. The character ‘*’ is a so-called wild card character that
can stand in for any string of characters (so the command doc* gives you all
documents that begin with doc).
You can delete a document with the command rm (remove) followed by the
document name (providing that you have a write access to the documents and
folders). For example, the command
hald(s001234) $ rm doc1
deletes the file doc1.
A document can be moved with the command mv (move). The same command
is used to change the name of a document. For example, the command
hald(s001234) $ mv doc2 dir.no.1/doc7
moves the document doc2 to the folder dir.no.1 and at the same time the
name will be changed to doc7.
Make and delete folders You can make a new folder with mkdir (make
directory). For example,
hald(s001234) $ mkdir newdir
makes a new folder with the name newdir. The command
hald(s001234) $ rmdir newdir
(remove directory) will delete it again. (A folder can only be deleted with this
command, if it is empty.)
If the folder contains files, the command
hald(s001234) $ rm -r newdir
(remove recursive) will delete the folder and all files and other folders under
it. 6
6 By default, G-Bar asks you to confirm every file that you you delete – And this may seem
like unnecessary work if you have several hundred files to delete. Thus, it is possible to work
around the protection default if you use the direct path rm:
hald(s001234) $ /bin/rm -r newdir
which deletes all files in the newdir without asking for confirmation before deleting each one.

6 The G-Bar 19
Making and changing documents ASCII files can be revised with an
editor, keying in the contents without hidden formating characters (as in Microsoft
Word and other application programs). This command is used, for
example, in writing programs and LATEX documents.
An editor that is simple to use is nedit. If you write
hald(s001234) $ nedit doc1
a window, which shows you the full contents of doc1 and in which you can
change the contents, opens
There are myriads of editors on the system. More advanced users often
prefer emacs, which is a powerful editor that knows the syntax for many programming
languages and also for LATEX.
Manuals about UNIX-commands There are a lot of UNIX commands,
and some of them are associated with a number of parameters.
A useful command that links to online manuals is man. For example,
hald(s001234) $ man cp
refers to online UNIX manuals and from there gives you a thorough explanation
of how to use the command cp for copying documents.
Sometimes it is still hard to know what command to use. In this case, it is
a good idea to use the command man -k with the keyword as the argument.
The command
hald(s001234) $ man -k copy
will, for example, give you a list of commands that can be used in connection
with copying. The list includes the command cp.
Another useful command like the man command is info, which gives a bit
more advanced information, and sometimes it also tells more about programs
than man does.
Other sources of information UNIX (incl. Linux) is being more and more
widely distributed, so there are a lot of other places to find information as well,
such as Google. At the G-Bar home page you can also find some good links to
information about UNIX.
6.5.3 Setting up a command environment
UNIX commands are executed in certain environments, and it can be useful for
the more experienced user to alter these environments. This section describes
briefly how to check the UNIX environment and alter it.

20 The Databar System at DTU
The commands are executed under a so-called shell. At DTU, that is usually
a bash-shell. Some other shells are the korn-shell and the C-shell. All of
the following notes relate to the bash-shell (but with small revisions could also
apply to the other shells).
When you log in to the system your environment is initialized. You can see
what your current environment is with the command env. The shell variable
PATH tells you what directories are searched in order to find programs.
There is a central setup, but experienced users can revise it in their own
personal setup by editing the files .profile and .bashrc, which are found in the
home directory. 7 .
In the file .bashrc, for example, you can easily add personal names to certain
UNIX commands or more complicated sequences. To add the following line
alias dir=’ls -F’
allows you to use a new command dir to list documents in a directory (after
the terminal has been closed and opened again, and provided that you are
using the bash-shell).
6.6 G-Bar software
6.6.1 Menu and terminal
The G-Bar offers users the access to a great range of programs. Most of which
can be accessed from the menu, and the rest of them accessible from the command
line. A complete list of programs is given on the G-Bar homepage:
http://www.gbar.dtu.dk/.
You may download software to your own computer at http://www.gbar.
dtu.dk/software/.
6.6.2 Microsoft Windows from the G-Bar
It is possible to start various Microsoft Windows applications 8 or a full Microsoft
Windows session from the G-Bar. Just go to ‘Microsoft’ in the menu.
The Windows server will ask for your user password every time that you
start an application directly from the G-Bar (SunRay session), unless you
logged in via a ThinLinc client. In that case, you can make use of ThinLinc’s
unique ‘single sign-on’ functionality.
Your home directory in the databar system will be drive ‘H:’ under Windows,
and you must not place data or programs anywhere else but on this
7 A document with a name that starts with a period is a “hidden” file. A list of hidden files
can be viewed, using the UNIX command ls -a
8 We currently support Word, Excel and Powerpoint from the menu.

6 The G-Bar 21
drive. 9 Most of the printers on the databar system will automatically be accessible
to you.
If you only need to read or write Word or Excel documents, it could be
advantageous to use StarOffice/OpenOffice directly in UNIX. The G-Bar Support
recommends to avoid using Windows programs, and instead to use the
programs that have been installed locally on G-Bar.
If you have OpenOffice or StarOffice installed on your own PC you will be
100% compatible with documents written at the G-Bar at DTU.
6.7 Printers
In the G-Bar, you have access to a long list of PostScript printers. Typically,
you will print from a program where you either key in the print command or
select a printer from a list. If a printer can’t be chosen directly in the program,
it is recommended that you use one of the printing commands xpp or gtklp.
In the program xpp, you can see a complete list of the accessible printer, and
the program can be started from the terminal:
hald(s001234) $ xpp
This list and different possibilities for printing in the G-Bar are also described
on http://www.gbar.dtu.dk/index.php/Printing_from_the_G-Bar. At last,
on this page you will find an instruction on how to install the G-Bar printers
on your own laptop, which makes it possible to print from your laptop.
6.8 Network commands
6.8.1 Text-based login on other computers
The command ssh stands for Secure SHell, and it is both a program and an
encrypted network protocol. It replaces programs such as rsh and telnet,
which are not encrypted and thus much less secure.
With ssh you can log in to the DTU systems from anywhere, and it may
look like this:
hald(s001234) $ ssh login.gbar.dtu.dk
After that, you will be asked for your password, and then you are logged in.
With ssh you have a lot of other possibilities such as portforwarding, forwarding
of X11 sessions etc. If you are interested in these options, go to the G-Bar
homepage or http://www.google.com/.
9 In fact, when using Microsoft Windows you can not see any other disks than the H:-drive.

22 The Databar System at DTU
In Windows, it is also possible to use ssh, although a third-party
application such as PuTTY is needed. You can download it at
http://www.chiark.greenend.org.uk/, and it is ready to go right away. To
use the client, you enter the name of the server you want to connect with, and
the protocol that you want to use. Example: To connect with the G-Bar server
Hald, use the following:
• Hostname – login.gbar.dtu.dk (〈servername〉.gbar.dtu.dk )
• Protocol – SSH
6.8.2 Transferring files by internet
In most instances, you will have files that you want to work at when you are at
home and at the G-Bar. Some like to use a diskette or a USB memory stick. But
lots of people at DTU just e-mail the files to themselves and then retrieve them
from their DTU mail. These solutions work all right in most cases, but there is
a much easier, faster, and more secure way to do it, which you can learn about
in the next section.
gftp The G-Bar has a graphic FTP client, called gftp.
The client starts either from the menu or with the command gftp, upon
which a window opens up something like the one in figure 4.
Figure 4: Screenshot of gftp

6 The G-Bar 23
Users who do not need a graphic client can use the classic command ftp or
the somewhat more advanced ncftp.
Note: FTP is a non-encryptd protocol. This means, all data (including user
ID and password) are sent through the internet unencrypted. Therefore, use
the encrypted SFTP (SSH) protocol!
scp scp stands for Secure CoPy and can be used, as the name implies, to
transfer files securely. This option is secure because all traffic is encrypted,
often with ssh. For the most part, the scp command is very similar to that of
cp, and it is scp 〈source〉 〈destination〉.
Copying local files to a remote computer:
hald(s001234) $ scp fil bruger@server:dir/file
or copying a file from a remote computer to the local server:
hald(s001234) $ scp bruger@server:dir/fil fil
For Windows users, the graphic client WinSCP can be recommended, and
it can be downloaded at http://winscp.net/eng/. As you can see in the Win-
SCP screenshot (Figure 5), the window is divided in two sections. The local
files are on the left side, and the remote files on the right. All you have to do is
“drag” the files from one side to the other to copy them back and forth. They
will be copied in the background with the command scp, which is encrypted
with ssh.
6.9 Job processing
This section is about the commands to use when you are running programs on
G-Bar, for example, in order to manage these processes.
Remember not to overload the system when processing a large number of
jobs and/or running parallel programs. It is permitted to do small test runs
on up to four processors for a short time (max. 10-15 minutes). Larger runs
must be processed under the control of a batch system. Read more about
this at http://www.gbar.dtu.dk/index.php/GridEngine. If you need more
resources, you may contact mailto:gbar-support@student.dtu.dk.
6.9.1 List of processes – ps
ps shows a list of the processes running on the machine that is currently in use.
Here is an example:

24 The Databar System at DTU
Figure 5: Screenshot of WinSCP
hald(s001234) $ ps -fu s001234
UID PID PPID C STIME TTY TIME CMD
s001234 16055 15989 0 10:09:42 pts/204 0:00 /usr/dt/bin/sdt_shell -c
s001234 16130 16122 0 10:09:42 pts/204 0:01 /usr/bin/gnome-session
s001234 16251 1 0 10:09:48 ? 0:05 gnome-panel
s001234 16253 1 0 10:09:48 ? 0:02 nautilus --no-default-window
s001234 16145 1 0 10:09:43 pts/204 0:01 /usr/lib/gconfd-2 12
s001234 16051 15989 0 10:09:42 ? 0:00 perl dtuinfo gray1:15 303.46.
s001234 16243 1 0 10:09:48 ? 0:01 gnome-smproxy --sm-client-id
s001234 16259 1 0 10:09:55 ? 0:00 /usr/lib/mixer_applet2
s001234 16245 1 0 10:09:48 ? 0:03 /usr/bin/metacity
s001234 15989 20421 0 10:09:40 ? 0:00 /bin/ksh /usr/dt/bin/Xsession
s001234 16148 1 0 10:09:44 pts/204 0:01 xscreensaver -nosplash
s001234 20417 591 0 Jul 22 ? 1:59 /usr/openwin/bin/Xsun :15
s001234 16023 1 0 10:09:41 ? 0:01 /opt/SUNWut/bin/utaudio
where -f means full, and -u means user. The above list only shows the processes
of the user s001234. 10
10 Note that the ps that is used as default in the G-Bar is part of Solaris and therefore behaves
differently than the default one in Linux. .

6 The G-Bar 25
6.9.2 Stopping a process – ctrl-c
The command ctrl-c is used to stop a process that is running from the command
line. Here is an example of usage:
hald(s001234) $ xcalc
[ctrl-c]
hald(s001234) $
6.9.3 Background and foreground processes
The ampersand symbol & after a command indicates that the program should
run in the background. This makes it possible to use the terminal window for
several processes at once. Example:
hald(s001234) $ firefox &
6.9.4 Killing a process – kill and xkill
If a process either gets hung up or runs amok, you can “kill” that particular
process. The next time you click on a graphic window after entering the command
xkill the related process will be “killed”. But you do not always have
a graphic window, so you will need to use the command ps to find out what
the process ID is, and then apply the command kill.
Example of usage:
hald(s001234) $ kill 12345
hald(s001234) $ kill -9 12345
Normally, a program will just be asked if it wants to shut down. This would
make it possible for the program to save a document. Placing a -9 before the
process number orders it to “kill” it immediately, which might be necessary if
the program has crashed or got hung up.
Note: Jobs which have been running for more than one CPU-hour will be
thrown out! You must not use more than 4 CPUs per job. If you have a job that
demands more, you have to use the batch system. For more on this subject,
please go to http://www.gbar.dtu.dk/index.php/GridEngine.

26 The Databar System at DTU
7 The Winbar
The Windows databars are based on Windows XP clients with high-resolution
monitors and CD/DVD burners. Many of them have dual monitors, great for
programming and viewing multiple documents, web pages etc. The clients
are real desktop computers and have their own procesor, RAM and a fairly
capable graphics adapter. This makes them very useful for high workload
tasks as long as the task does not take more than a couple of hours at most.
There are a group of Windows 2003/2008 servers that among other things
provide user authentication, store your documents and other data and grant
access to printers.
7.1 Documents
Study-related data can be saved on the H-drive (documents that are saved in
“My Documents” are automatically saved on the H-drive). If you save your
data there, it will be accessible from any client in the Windows databars. Each
user is allowed to save a maximum of 500 MB of data on the H-drive, and
if you save more, you will get a warning when you log on. If you do not
delete data to get under 500 MB, your account will be closed. Only data and
programs that are study-related are allowed to be saved.
It is possible to access the H-drive from your laptop or at home by connecting
directly to the Winbar servers. Please see http://www.winbar.dtu.dk/ for
more info.
The I-drive is connected to your “UNIX home drive”, and the files that
you see on the UNIX clients are placed there. This drive is accesible from
any computer, as described in section 6.8.2 on page 22. You are allowed to
save a maximum of 1 GB of data on the I-drive. You should be aware that
everyone can see the files, that are placed in the root of the I-drive, unless
you have changed the rights (for more information about file permissions, see
http://www.gbar.dtu.dk/).
7.2 Installation of software in the Winbar
The programs that are most frequently used in the databars are automatically
installed. The rest of the programs can be installed by finding “Installation of
programs” on the desktop, navigate to the program that you wish to install
and activate the program. The installation of the program is hereafter automatic.
Normally, the installation does not take more than one minute, and
more than 180 different programs are available.

7 The Winbar 27
7.3 Formatting
If problems occur on the computer, it is possible to format the computer by
presseing the “Symantec Ghost Client”-button in the bottom right corner and
choosing “Reinstall Windows...”. It will take approximately 10 min.
7.4 Printers
When you want to print, the computer will by default choose the printer that is
closest to you. It is possible to see a list of all printers in the Winbar in: “Start”
→ “Printers and Faxes”.
If you want to print on the Wireless in the Winbar, read the guide on http:
//www.winbar.dtu.dk.
7.5 Scanners
Scanners are available in several rooms in the Winbar, see the complete list on
http://www.winbar.dtu.dk. On each scanner, there is a label that indicates
the home page of the scanner. Open an Internet browser, and navigate to this
home page. Next, put the material that you wish to scan in the scanner. On
the home page you may choose between PDF, JPG or TIFF format, and choose
black/white or colour. When you have chosen the format, press “Scan”. If
the scanner is in hibernation mode, it will take up to 30 seconds before the
scanned material will appear on the screen. Afterwards, you can save it where
you want. Only scan from computers that are in the same room as the scanner.
It is not possible to scan from Wireless.
7.6 UNIX from Winbar
If you want to run UNIX applications from a Windows PC, you can open a
ThinLinc session and open a desktop-connection to the G-Bar, as described in
section 5 on page 8.

28 The Databar System at DTU
8 Linux
Linux is an operating system originally conceived by Linus Torvalds and
subsequently developed under Open Source principles. The source code for
Linux, contrary to Microsoft Windows, is freely accessible. This means, a very
large number of people have reviewed the code and checked it for security
flaws, back doors left open, and other sources of trouble.
Many have considered Linux to be an alternative suitable only for nerds.
In recent years though, opinions have been drastically revised. It can be just
as easy to install and use Linux as Microsoft Windows. The only difference is
that you have a lot more choices if you choose to base your system on Linux.
In addition to that, Linux as well as most of the programs that run on Linux
are free of cost!
Linux is to a high degree Unix-like, so it will not take long before it is totally
clear to you how to hook up your own PC to the G-Bar system. In the G-Bar,
we can help you with the following distributions 11 :
• Ubuntu Linux
• Debian Linux
You can also come to see us at our office in Building 308 if you to have
further problems. We strive to always have installation CDs for the Ubuntu
Linux distribution that you may freely acquire at our office.
8.1 Linux programs
At DTU, we use a number of programs in connection with courses, and students
can acquire some of them either free of cost or at a modest price. The
G-Bar tries to collect the software that DTU offers. See our software page:
http://www.gbar.dtu.dk/software/
Other internet pages worthy of mention are http://www.sourceforge.net/
and http://www.freshmeat.net/. If you are missing software that happens
not to be included in the distribution you are using, you might be able to find
it there. Most of the software on these pages is free of cost 12 and written for the
Linux/Unix environment. But you can also find both Windows and Mac software
there. However, installing from these pages can be a little more difficult,
so beginners might need help with it.
11Check http://www.distrowatch.com/ to see some of the many different distributions
that are available.
12SourceForge requires that programs offered there are Open Source.

9 Mac at DTU 29
8.2 DTU-LUG
In the Linux world, people are good at getting themselves organized and also
helping others. This among other things can be done at LUGs. LUG stands for
Linux User Group. There is one at DTU too, and it is called DTU-LUG. They
throw an Install Party at the beginning of each semester. For more about that,
go to http://dtulug.dtu.dk/.
9 Mac at DTU
Conditions are good for Mac users at DTU. You can connect to the databars
from your Mac and run the programs used in the courses on your Mac. You
can also print to the databar printers directly from your Mac.
9.1 MacVærk
A group of Mac users, called MacVærk, meet once a week, and their meetings
are a good place to get help, if you have any questions about using a Mac at
DTU. These meetings are every Tuesday evening, 6 pm at S-Huset.
MacVærk arranges an information event soon after the semester has begun
too, and there you can find out what possibilities are available. They have
placed a number of Macs at the disposal of all DTU students at S-huset in
Kaffestuen, and these are frequently used.
Otherwise, MacVærk also organizes events that are more or less related to
Mac use.
We, at MacVærk, would be glad to see you at our information event. Find
out more at http://macvaerk.dtu.dk/.

Index
CampusNet, 7
computing servers, 9
databars, 5
at DTU, 6
directory, 16
delete, 18
make, 18
document
copy, 17
delete, 17
editing, 19
move, 17
e-mail, 13
access student mail, 13
forwarding of e-mail, 14
in G-Bar
graphical, 13
textbased, 13
editor, 19
Eduroam, 5
file system, 14
filebrowser
ROX, 11
folders
switch between, 17
FTP, 22
gftp, 22
Secure CoPy (scp), 23
WinSCP, 23
G-Bar
hardware, 9
menu, 11
servers, 9
support, 7
Helpdesk, 7
30
High Performance Computing, 9
IceWM, 11
desktops, 12
themes, 12
windows, 12
internet browser, 12
Firefox, 12
Opera, 12
job processing, 23
background and foreground processes,
25
kill a process, 25
larger jobs, 23, 25
list of processes, 23
stop a proces, 25
Linux, 28
DTU-LUG, 29
programs for, 28
user group, 29
login, 9
logout, 10
Mac, 29
Mac OS X, 29
MacVærk, 29
user group, 29
manual pages, 19
mappe
delete, 18
make, 18
Microsoft, 20
Excel, 20
home folder, 20
Powerpoint, 20
Windows, 20
Word, 20
on-line help, 19

INDEX 31
password
change, 10
forgotten password, 7
portable computers, 5
Portalen, 7
print, 21
from laptop, 21
in G-Bar, 21
in Winbar, 27
program
editing, 19
start from menu, 11
remote graphical login, 8
setup, 19
command environment, 19
shell, 19
bash-shell, 19
Smart-card, 9
software, 20
download, 20
in G-Bar, 20
StarOffice/OpenOffice, 21
ssh, 21
PuTTY, 22
support, 7
for G-Bar, 7
for Winbar, 7
terminal, 10
thin client, 5
ThinLinc, 5, 8, 20, 27
UNIX, 14, 19
commands, 15
directory, 16
file system, 14
home folder, 15, 26
user interface, 10
IceWM, 11
Menu, 10
Winbar, 26
print, 27
scan, 27
software, 26
UNIX from, 27
Window Manager
IceWM, 11
Windows, 12
wireless network, 5
xfe, 11

32 The Databar System at DTU
The G-Bar homepage: http://www.gbar.dtu.dk/
The Winbar homepage: http://www.winbar.dtu.dk/
G-Bar software download: http://www.gbar.dtu.dk/software/
Campusnet: http://www.cn.dtu.dk/
Wireless ESSID: Eduroam
Alternative Wireless ESSID: DTU
LATEXat DTU: http://www.student.dtu.dk/~latex/
DTU Linux User Group: http://dtulug.dtu.dk/
DTU Mac User Group: http://macvaerk.dtu.dk
General IT Support: itsupport@student.dtu.dk
G-Bar Support: gbar-support@student.dtu.dk
Winbar Support: dbsupport@winbar.dtu.dk