CSS307-System Programming Suleyman Demirel University Fall 2014 by - - PowerPoint PPT Presentation

CSS307-System Programming

Suleyman Demirel University Fall 2014

by Konstantin Latuta & EN3([ABCDEF]|KZ)04

Week03 – GUI review and Introduction to Week03 – GUI review and Introduction to Command Line Command Line

• Learning Goals

– Learning some HowTos's of GNOME and Ubuntu 14.04 – Learning basic Linux shell commands and concepts

GNOME Desktop Environment

• GNOME is a popular desktop

environment that is default for many distributions

• Alternatives:

– KDE – Unity (based on GNOME) – Xfce – LXDE

• Display manager for GNOME is gdm.

Others are lightdm (by Ubuntu) and kdm (KDE)

GNOME desktop on

• lder

Ubuntu, may be 10.04

HowTo's using GUI

• Login/Logout, suspend, shutdown...
• Locking (Ctrl+Alt+L), account switching...
• Default Applications...
• Locating Applications: press dash and write what you are looking for...
• User directories /home/user
• Nautilus shortcuts, Ctrl+1, Ctrl+2, Ctrl+L, Ctrl+H …
• Alt+F2 to run a command...
• Ctrl+Alt+T to invoke terminal...
• Deleting files … ~/.local/share/Trash/files
• Changing appearance...

Date and Time

• Network Time Protocol (NTP) - is the most popular and reliable

protocol for setting the local time via Internet servers

• Detailed configuration should go here: /etc/ntp.conf

Network Manager

• Network Manager utility was developed to make things easier

and more uniform across distributions

• Supports many VPN technologies

– PSec, Cisco OpenConnect,

Microsoft PPTP and OpenVPN.

Installing and Updating Software

• A package in a Linux

distribution provides one piece

• f the system, such as the

Linux kernel, the C compiler, the shared software code for interacting with USB devices,

• r the Firefox web browser
• Packages are often dependent
• n other packages...

Debian Package Management

• dpkg - can install, remove, and

build packages but can not automatically download and satisfy all dependencies.

• apt (Advanced Package Tool) – a

higher level package management system... generally tools are build upon it like apt-get, aptitude, synaptic, Ubuntu Software Center, Update Manager

Red Hat Packet Manager

• penSUSE’s YaST Software Management

Command Line Prompt

• Linux System Administrators spend their lives at a command line

prompt (terminal emulator or virtual terminal)

• Advantages:

– No GUI overhead. – Virtually every task can be accomplished using the command line. – You can script tasks and series of procedures. – You can log on remotely to networked machines anywhere on the Internet. – You can initiate graphical apps directly from the command line.

Terminal Emulator

• A terminal emulator program

emulates (simulates) a stand alone terminal within a window on the desktop

–

gnome-terminal

–

xterm

–

konsole

–

Terminator

• To launch your default terminal

press Ctrl-Alt-T in Ubuntu

• You can drop X Window

graphical interface or start it up again, as you wish..

• Ubuntu distinguishes

between servers (without X) and desktops (with X)

The X Window System

Virtual Terminals

• VTs are console sessions that use

the entire display and keyboard

• utside of a graphical environment
• “virtual” because although there can

be multiple active terminals, only one terminal remains visible at a time..

• One virtual terminal is reserved for

the graphical environment

– VT7 in Ubuntu and VT1 in

CentOS/RHEL and openSUSE

The Command Line

• Command

–

name of the program you are executing ls -a Desktop

• Options

–

switches to modify what the command may do

–

Usually start with one or two dashes ls -a Desktop ls --all Desktop

• Arguments

–

Represent what the command operates on ls -a Desktop

Turning off GUI :)

• sudo service gdm stop

– most GNOME desktops

• sudo service lightdm stop

– Ubuntu

• sudo telinit 3

– RPM-based, like openSUSE or CentOS

basic operations in the shell terminal

Rebooting and Shutting Down

• halt, poweroff

shutdown -h

• reboot

shutdown -r

• shutdown -h 10:00 "shutting down for scheduled

maintenance"

Locating Applications

Accessing Directories

• pwd displays present working directory (echo $PWD also

works)

• echo $HOME shows your home directory = default place

where you end up after logging in.

• cd ~ or cd changes to your home directory
• cd .. changes to parent directory
• cd - changes to previous directory

Absolute vs Relative Paths

• Absolute paths always start with /

/home/konst/Desktop/hello.cpp /home////konst//Desktop/hello.cpp is also valid ...

• Relative pathname starts from the present working directory

. present directory .. parent directory ~ your home directory ../../Desktop/hello.cpp

Exploring filesystem

• cd / changes your current directory to root (/)
• ls lists the content of the present working directory
• ls -a lists all files including hidden ones (those whose name

start with .)

• tree displays a tree view of the system (if the command is not

present install it with sudo apt-get install tree)

Hard and Soft (Symbolic) Links

• A symbolic link is a pseudo-file which behaves as an alternative

name for some other file or directory

• The “contents” of the symlink are the real name pointed to
• When you try to use a file name including a symlink, the kernel

replaces the symlink component with its ‘contents’ and starts again

• Symlinks allow you to keep a file (or directory) in one place, but

pretend it lives in another

Hard and Soft (Symbolic) Links

• Hard link is an alternative path to a file equally important as any
• ther path
• Two files that have same inode number are hard links of each
• ther

– An inode is the data structure that describes a file on disk – It contains information about the file, including its type

(file/directory/device), modification time, permissions, etc.

– A directory entry contains a name and an inode number

• So a file’s name is not considered to be part of the file itself

e.g. 2to3 is a symlink to 2to3-2.7 in /usr/bin

Creating a symlink..

Creating a hard link...

References

• Linux System Administration: modules 1-6, 12 and 13
• Linux Essentials: Chapters 3, 4 and 6