Linux commandsppowershel1-LHC_School.ppt

19/05/2024 1
Linux Lecture – 01
Sharjeel Kashif

19/05/2024 Sharjeel Kashif, NCP 2
Today’s Lecture
• Operating System Concept
• Brief History of UNIX & Linux
• A Linux Distribution
• Architecture of Linux
• Basic Principals of Linux
• Linux File System
• Typical Linux Directory Structure
• How to login
• Basic Linux Commands

Operating System Concept
• An operating system (OS) is
a resource manager
• It is a set of software
routines:
– that allow users and
application programs to access
system resources
– in a safe, efficient and abstract
way
– CPU, memory, disks, modems,
printers network cards etc.
• A general operating system
architecture can be
understood by the figure
Users
Shell or GUI
Application
Programs
System Utilities
System Call Library
Operating System Kernel
Dual Processor with 2 GB RAM,
160 GB Hard Disk

Operating System Concept
• The kernel controls the hardware
• It provides functions like
– Handling of interrupts from the devices
– Allocation of memory to programs
– Sharing of CPU among the programs
• Basic kernel services are exposed to higher-level programs
through a library of system calls
• Application Programs and System Utility Programs
make use of system calls
– Launched using a shell/GUI
• The OS may differ from one another on the basis of:
– System calls
– System utilities
– User interface they provide
– Resource scheduling policies implemented by the kernel

History of UNIX & Linux
• In late 1960s, MULTICS was introduced for
mainframe computers
• Joint venture of GE, MIT and Bell Labs
• Inspired Ken Thompson – who wrote simpler
version called UNICS, which evolved into UNIX
• Ken Thompson with Dennis Ritchie in 1973 wrote
the UNIX kernel in C
• The Fifth edition of UNIX was released to
universities in 1974
• In 1978, UNIX development was split into two main
branches:
– SYSV
– BSD

• Linux – open source OS for PCs
• Developed by Linus Torvalds (a Finnish graduate student),
in 1991
• Neither pure SYSV nor BSD, mix of both
• Conforms to a set of standards called POSIX
• Code freely available, anyone can:
– Modify, add features, correct deficiencies
• Different Distributions:
– Caldera Systems Corel Debian Mandrake
– Red Hat Slackware Strom SUSE
– Turbo Gentoo Stampede Knoppix
– Fedora Ubuntu College Linux White Box Linux
History of UNIX & Linux

A Linux Distribution
• A distribution comprises of:
– Kernel
• 2.6.9-89.0.11.EL.cernsmp
– System Utilities
• File copy, hard disk repair/defragment etc.
– GUI
• GNOME, KDE
– Application Programs
• Open office, evolution, firefox, gedit, gftp. konqueror,
evince, kdevelop, kview, emace, vim etc.

Architecture of Linux
• Kernel
– Initializes the device drivers
– Processor & memory management functions
– Support for many different type of file systems
– A wide range of system calls (mix of SYS V, BSD and POSIX.1)
– Loaded into the memory at system startup
– Location /boot/vmlinuz
– Source files /usr/src/linux
• Shells & GUIs
– Textual command line shells
• bourne shell (sh), bourne again shell (bash)
• csh and tcsh
– GUI Environment
• GNOME and KDE

Architecture of Linux
• System Utilities
– ls, grep, sed, awk, less, bc, wc, more etc.
– Powerful tools that perform a single task
extremely well
– Can also chain programs together using pipes
– Server programs called daemons
• Application Programs
– emacs, vi, kdevelop, gcc, g++, open/star office
etc.

Basic Principals of Linux
• Everything is a file
• Small, single purpose programs
• Ability to chain programs to perform complex
tasks
• Avoid captive user interface
• Configuration data is stored in text
• Linux is case-sensitive

Linux File System
• Every file in Linux can be one of the
following four types:
– Ordinary File (contain data, info)
– Directories (hold files & other directories)
– Devices (for accessing the hardware)
– Links (Pointer to another file)
• Hard Link
• Soft Link

Typical Directory Structure
• Linux Filesystem is laid out in a hierarchical tree
structure.
• Top level directory is called root “/”

/bin: Binary files
• /bin contains commands that may be used by both
the system administrator and by users

/bin: Binary files

/sbin: Super-user Binaries
• This directory contains the binaries used by the
root user
/boot: Boot files
• This directory contains everything required for
the boot process except configuration files

/dev : Device files
• The /dev directory is the location of special
or device files
/proc : Virtual File System
• The /proc directory contains directories and
files that report system information and
status

/etc: Configuration files
• /etc contains configuration files and directories.

/home: User area
• /home contains user home directories
• Area writable by individual users
• Others users may be able to read depending
upon permissions

/lib: Library files
• /lib contains essential shared libraries and
kernel modules.
• The /lib directory contains those shared library
images needed to boot the system and run the
commands in the root filesystem, i.e., by
binaries in /bin and /sbin.

/mnt: Mount area
• Mount point for a temporarily mounted
filesystem.
• This directory is provided so that the system
administrator may temporarily mount a
filesystem as needed.
• The content of this directory is a local issue
and should not affect the manner in which
any program is run.

/root & /tmp
• The /root is a home directory for the root user
• The /tmp directory must be made available for
programs that require temporary files
• /tmp is writable by everyone i.e. world writable

/usr/lib: Library files
• Libraries for programming and packages.
• /usr/lib includes object files, libraries, and
internal binaries that are not intended to be
executed directly by users or shell scripts.

Summary: Directory Structure
• Home Directories: /root,/home/username
• User Executables: /bin, /usr/bin, /usr/local/bin
• System Executables: /sbin, /usr/sbin, /usr/local/sbin
• Other Mountpoints: /media, /mnt
• Configuration: /etc
• Temporary Files: /tmp
• Kernels and Bootloader: /boot
• Server Data: /var, /srv
• System Information: /proc, /sys
• Shared Libraries: /lib, /usr/lib, /usr/local/lib

Logging into a Linux System
• Two types of login screens
– virtual consoles (text-based)
– graphical logins (display managers)
• Login using login name and password
• Each user has a home directory for personal
file storage

Absolute & Relative Paths
• Absolute pathnames
– Begin with a forward slash
– Complete "road map" to file location
– Can be used anytime you wish to specify a file
name
• Relative pathnames
– Do not begin with a slash
– Specify location relative to your current working
directory
– Can be used as a shorter way to specify a file
name

Basic Linux Commands
• ls, listing files and directories
– ls –a
– ls –l
– ls –C
– ls –F
– ls --color
– ls –d
– ls –g
– ls –o
– ls –h
– ls –lh, ls –CaF

• cd, change directory
– cd ..
– cd –
– cd ~/mydir
– cd /home/usman
– cd
• su, switch user, su – (complete user
environment)
• id, print user and group ids
• passwd, change password
– yppasswd

• man, manual pages
– man <command>
• info, information pages
– info <command>
• command --help, basic help by author
– ls --help, man --help
• pwd, present working directory

• ps, process information
– ps aux
– pstree
– ps fax
– top
• free, memory information
– free –m
• cal, calendar information
– cal, cal 2009
• head, output the first part of files
– head [-n <lines>] <filename>
• tail, output the last part of files
– tail [-n <lines>] <filename>

• cat, concatenate/display files
– cat /home/usman/myfile
• clear, clears the screen
• date, see/modify system date & time
– date, date [MMDDhhmm[[CC]YY][.ss]]
• df, disk space usage
– df –h
• du, file space usage
– du –sh
• uname, print system info
– uname [-a, -s, -n, -r, -v, -m]

• echo, display a line or text
– echo “any text”, echo $HOSTNAME
• exit, exit the current session/shell
• file, determine file type
– file <file name/path>
• hostname, show or set the system hostname
– hostname [<new-name>]
• more, file perusal filter for CRT viewing
– more <file name/path>
• less, file perusal filter
– less <file name/path>

• cp, copy files and directories
– cp [options] file destination
• More than one file may be copied at a time if the
destination is a directory:
– cp [options] file1 file2 destination
• If the destination is a directory, the copy is placed
there
• If the destination is a file, the copy overwrites the
destination
• If the destination does not exist, the copy is renamed

• mv, move and/or rename files and directories
– mv [options] file destination
• More than one file may be moved at a time if
the destination is a directory:
– mv [options] file1 file2 destination
• In mv also, the destination works like cp
• mkdir, creates directories
– mkdir <directory name/path>
• rmdir, removes empty directories
– rmdir < directory name/path>

• touch, create empty files or update file
timestamps
– touch <file name/path>
• rm, remove files
– rm [options] <file name/path>
– rm -i file (interactive)
– rm -r directory (recursive)
– rm -f file (force)
• rm –r, recursively removes directory trees
– rm –rf <directory name/path>

• chsh, change your login shell
• alias, setting command aliases
– alias ll=‘ls –l’
• whoami, print user id
• find, finding files and directories
– find <path> –iname <file name>
– find <path> -size +100
– find <path> -user usman –o –group it
– find <path> -perm 755

File Permissions in Linux
Octal Binary Permissions
0 000 _ _ _
1 001 _ _ x
2 010 _ w _
3 011 _ w x
4 100 r _ _
5 101 r _ x
6 110 r w _
7 111 r w x

• chmod, changing permissions of files/directories
– Octal mode
• chmod 644 <file name/path>
– Symbolic mode
• chmod u+x, g-r, o+x <file name/path>
• chmod a+x <file name/path>
• chmod =x <file name/path>
• chown, changing ownership of files/directories
• chgrp, changing group ownership of files/directories
– chown usman <file name>
– chgrp it <file name>
– chown usman.it <file name>

• stat, display the file status
– stat <file name/path>
• ssh, Open SSH client for remote login
– ssh <username>@<hostname>
– ssh –l <username> <hostname>
– ssh <hostname>
• scp, secure copy (remote file copy)
– scp <file name>
<username>@<hostname>:<path>
– scp <username>@<hostname>:<path> <local
path>

• env/setenv, adding or changing a variable
• Setting variable values
– MYVAR=“something”
– echo $MYVAR
– bash shell
• export MYVAR=“something”
– tcsh shell
• setenv MYVAR “soemthing”
• Sourcing files
– source /home/env/my_env.csh
– . /home/env/my_env.sh

• ln, creating links
– ln <source file name/path> <link name>
– ln –s <source file name/path> <link name>
• .bashrc (bash shell)
– For setting local variables and aliases
• .tcshrc (tcsh shell)
• .chsrc (csh shell)

Shell Scripting Basics
#!/bin/sh
echo “Welcome to Linux -- ” $USER
echo “Today is : ” $(date)
echo “You are working in : ” `pwd`
echo “Enter your last name: ”
read LNAME
echo "Hello -- $LNAME”
read X
read Y
echo “The product is : $X*$Y “
echo “Bye Bye…”

Shell Scripting Basics
• #!/bin/sh
MSG=“Assignments due today…”
for i in $(cat ~/users) ; do
NAME=$i
EMAIL_ADD=$NAME@ncp.edu.pk
echo $MSG | mail –s “Warning” EMAIL_ADD
done

Thank you
Q & A

Linux commandsppowershel1-LHC_School.ppt

More Related Content

Similar to Linux commandsppowershel1-LHC_School.ppt (20)

Recently uploaded (20)

Linux commandsppowershel1-LHC_School.ppt