C2110 UNIX and programming Lesson 1 / Module 4 -1C2110
UNIX and programming
Petr Kulhanek
kulhanek@chemi.muni.cz
National Center for Biomolecular Research, Faculty of Science
Masaryk University, Kamenice 5, CZ-62500 Brno
Lesson 1 / Module 4
PS / 2020 Distance form of teaching: Rev2
C2110 UNIX and programming Lesson 1 / Module 4 -2First
Steps
➢ Local vs remote access
➢ Local login
➢ Terminals
➢ Command line
➢ Remote login, command ssh
C2110 UNIX and programming Lesson 1 / Module 4 -3Local
vs Remote Access
user
local session
user
local session
Remote Access
C2110 UNIX and programming Lesson 1 / Module 4 -4Local
Login
Local terminals (historical order):
• six text terminals (F1 ... F6)
• one graphical terminal (F7, F8, ...)
• toggled using the keys Ctrl + Alt + F1 ... Ctrl + Alt + F7
Local terminals (new order, Ubuntu > 18.04):
• login to graphic terminal (F1)
• graphic terminals - according to use (F2, F3,…)
• text terminals - according to use (F2, F3,…)
• toggle using the keys Ctrl + Alt + F1 ... Ctrl + Alt + F7
Login:
• loginname (username) and password (password)
must be entered
The Linux operating system is very flexible and allows other ways of local login, such as
using identification cards or cryptographic keys. More can be found in the help of PAM
system (Pluggable Authentication Modules). $ man 8 pam
C2110 UNIX and programming Lesson 1 / Module 4 -5Local
Login
Text terminal
➢ makes the command line (CLI - command line interface)
➢ the default directory is /home/username (home directory)
➢ graphics applications (X11) can only be run with export the display to a
remote graphics terminal
➢ log off command exit
Graphic terminal
➢ starts X11 server or Wayland composer and the window manager (KDE, Unity,
GNOME, etc.)
➢ window manager (desktop environment) can be selected before self login
➢ allows direct launch of graphical programs (GUI - graphical user interface)
➢ the command line is available through special applications
➢ xterm
➢ console
➢ gnome-terminal
➢ log out using the menu in the menu window manager
C2110 UNIX and programming Lesson 1 / Module 4 -6Local
Login
Login Name (Enter)
The default keyboard is English (EN).
When using the numeric keypad, make sure NumLock is turned on.
Password (Enter)
Ability to change the type of desktop
environment
(gnome, KDE, etc., some must be
installed first)
Ubuntu 18.04 LTS
Login screen for graphics
terminal (GUI)
C2110 UNIX and programming Lesson 1 / Module 4 -7GNOME
Desktop
Settings,
logout, shutdown
Standard
applications
Dock
(running applications,
frequently used
applications)
Terminal
C2110 UNIX and programming Lesson 1 / Module 4 -8-
Terminals
The command line is accessible directly from text terminals. In a graphical environment
(X11/Wayland), it is necessary to run a suitable application emulating a text terminal:
➢ gnome-terminal (Terminal)
➢ console
➢ xterm
console
The default directory is: /home/username
simple, yet highly
configurable
gnome-terminal
simple, standard on all
UNIX systems
xterm
C2110 UNIX and programming Lesson 1 / Module 4 -9Command
Line
[kulhanek@wolf ~]$
username
computer name
current directory (~ means home directory /home/username)
Prompt - type of user / prompt ($ regular user, # super user, other possible %, >)
place for command
The command is executed by pressing the Enter key.
Copying text: Do not use Ctrl + C! To copy text from the terminal, just highlight the text,
press the mouse wheel (middle button) to paste it.
Autocomplete: by pressing the Tab key (tab) the command line interpreter tries to
complete the spelled word. Command names, paths and file names are added (if one press
does not cause anything, there are more options to add, repeated press will display them).
History: Use the up and down arrow keys to scroll through the list of commands you have
already entered. The command s from the history can be reused or modified and then used
in the modified form. The history is also accessible by command history.
C2110 UNIX and programming Lesson 1 / Module 4 -10Remote
Login
➢ ssh
➢ nested login
C2110 UNIX and programming Lesson 1 / Module 4 -11Remote
Login
There are several remote login options (rsh, XDMCP, etc.) but the most used and
the safest is the use of the ssh command (secure shell).
$ ssh [user@]hostname [command]
Syntax:
username;
if not specified, the name of the
logged in user will be used
computer name
[] - can be omitted
Log out:
The remote interactive login (session) is
terminated by the command exit.
Examples of use:
$ ssh wolf01.ncbr.muni.cz
$ ssh wolf01 who
the command to be executed; if
not specified, the command line is
made available in interactive mode
C2110 UNIX and programming Lesson 1 / Module 4 -12Initial
Remote Login
[kulhanek@pes ~]$ ssh skirit.ics.muni.cz
The authenticity of host 'skirit.ics.muni.cz
(2001:718:ff01:1:216:3eff:fe20:382)' can't be established.
ECDSA key fingerprint is SHA256:Splg9bGTNCeVSLE0E4tB30pcLS80sWuv0ezHrH1p0xE.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added 'skirit.ics.muni.cz' (ECDSA) to the list of known
hosts.
[kulhanek@skirit ~]$
When logging in for the first time, it is necessary to confirm the authenticity of
the machine we are logging to. In a trusted network, we can accept the
fingerprint without verification. However, it is a good idea to verify the machine's
fingerprint in an independent way (for example, by sending a thumbprint by mail
from the remote machine administrator) in an insecure environment.
This is protection against MITM (Man-in-the-middle) attack.
Note:
On a WOLF cluster, all computers are verified against each other, so this confirmation is not
required.
C2110 UNIX and programming Lesson 1 / Module 4 -13Remote
Login
wolf03 wolf04 wolf05wolf02
wolf06 wolf07 wolf08 wolf23
Using the command ssh, it is possible to do nested remote login.
ssh wolf07
ssh wolf02
ssh wolf03
ssh wolf03
With each new level of remote login overhead grows, therefore, if possible, we will use
the most direct remote login.
Nested remote login must be used to access computers on non-public networks (e.g.,
supercomputers in IT4I). (details in supercomputing C2115).
C2110 UNIX and programming Lesson 1 / Module 4 -14WOLF
Cluster - Where to login?
wolf wolf03 wolf23wolf02 wolfsr
university
network
workstations (computing nodes)
server / front
node
0.18 1.18 2.11
wolf32 wolf40wolf31wolf30
0.18
wolf01
switch
computing nodes
wolflr
0.57
Full machine names:
wolf02.ncbr.muni.cz
wolf03.ncbr.muni.cz
….
wolf23.ncbr.muni.cz
Short machine names (only within the WOLF cluster):
wolf02
wolf03
….
wolf23
C2110 UNIX and programming Lesson 1 / Module 4 -15Exercise
1
1. Remotely login onto the workstation wolf02.ncbr.muni.cz
• From MS Windows (any version) use Putty (see separate presentation)
• From Linux or macOS, use the command ssh
2. Verify the remote workstation name using the command: hostname
3. Print the full computer name using: hostname -f
4. Print your login name: whoami
5. List the logged users: w or who or last
6. List the contents of your home directory: ls
7. Print the path to your home directory: pwd
8. From the node wolf02 log on to the node wolf10 via the command ssh.
9. Repeat tasks 2 through 7 on node wolf10.
10. Log out from the wolf10 node: exit
11. From the node wolf02 run the command hostname remotely on the node
wolf16.
12. From the node wolf02 run the command ls remotely on the node wolf16.
13. Log out from the node wolf02: exit
C2110 UNIX and programming Lesson 1 / Module 4 -16-
wolf10
Exercise 2
1. Open two terminal sessions on the workstation wolf02.ncbr.muni.cz
2. Enter commands from a previous exercise (e.g. last, w, etc.).
3. Sign out.
1. Open two terminal sessions, one on the workstation wolf02.ncbr.muni.cz and
the other on wolf10.ncbr.muni.cz
2. Enter commands from a previous exercise (e.g. last, w, etc.).
3. Sign out.
wolf02wolf02
wolf02
wolf02
wolf02
wolf10
your computer
your computer