Linux fundamental day 2 train with shubham

 Linux Founder—Linus Torvalds

Linus Benedict Torvalds is a Finnish software engineer best known

for having initiated the development of the Linux kernel and git

revision control system.

History of LINUX

Linux came from a Unix family, Linux is free and open-source

software operating systems, which was developed by Linus

Torvalds in September 1991.

In 1991, When Linus Torvalds was a student at the University

of Helsinki, Finland, USA.

He developed the first code of Linux 0.01 and post it on Minix

newsgroup 17 Sep 1991, his code become so popular

people encourage him to develop new code and he was lead

to develop new code and release the first “official” version of

Linux, version 0.02 on October 5, 1991.

Today many year pass and Linux become one of the most

popular operating system.



Today 90% fastest Supercomputers out of 500 run on Linux

variant including top 10.

Linux File System Hierarchy

+ In Linux everything is represented as a file including a

hardware program, the files are stored in a directory, and every

directory contains a file with a tree structure. That is called File

System Hierarchy.

+ Linux uses single rooted, inverted tree-like structure.

+ Root Directory represents with / (forward slash) It is a top-level

directory in Linux.



+ The base of the Linux directory is the root. This is the starting

point of FSH. Every directory arises from the root directory. It is

represented by a forward slash (/).

+ If someone says to look into the slash directory, they refer to the

root directory.

/root

 Itis the home directory for the root user (superuser).

/bin > User Binaries

 Contains binary executable.

+Common Linux commands you need to use in single-user

modes are located under

this directory.



 Commands used by all the users of the system are located here.

/sbin > System Binaries

Just like /bin, /sbin also contains binary executables.

 But, the linux commands located under this directory are used

typically by system aministrator, for system maintenance

purpose.

For example: iptables, reboot, fdisk, ifconfig, swapon

/dev > Device Files

it contains hardware device files,

Contains device files.

These include terminal devices, usb, or any device attached to

the system.

 For example: /dev/tty1, /dev/usbmon0

/var> Variable Files

The variable data files such as log files are located in the /var

directory.



File contents that tend to grow are located in this directory.

> This includes

» /var/log: System log files generated by OS and other applications.

» /var/lib: Contains database and packages files.

¢ /var/mail: Contains Emails.

° /var/tmp: Contains Temporary files needed for reboot.

/mnt> Mount Directory

 This directory is used to mount a file system temporarily.

/media> Removable Media Devices

The /media directory contains subdirectories where removable

media devices inserted into the computer are mounted.

/usr> User Binaries



directory.

#uname > it shows the name of the kernel (OS)

#uname -r > it shows version of the kernel

#cd > it use for change directory

#clear > it use for clear screen

#whoami > it show currently login user name

#history > it show list of previously used commands

#date > it show time and date

Create file or directory

1. For create single directory

#mkdir /shubham

2. For create multiple directory

#mkdir dev qa test

3. For create directory path (directory inside directory)

#mkdir -p /dev/qa/test/devops

4. For create number of directory

#mkdir /student{1..10}



Create file

Touch:

Touch command is use for create empty file, we can’t write data in a

file, can’t edit or save file.

1. Create single file with touch command

#touch notes

2. Create multilpe file

#touch python java react

3.Create number of files

#touch books{1..10}

For copy and paste

cp:

cp command is used for copy and paste file or directory



Syntax:

#cp <option> <source> <destination>

Options

-t for recursive

-v for verbose

-f for forcefully

For copy file

#cp -rvf /root/anaconda-ks.cfg /home

For copy all data which start form D alphabet

#cp -rvf /root/D* /home

For remove file & directory

For delete file or directory

#rm -rvf /india/pune

For move or rename file & directory

For move file or directory

#mv /home/shub/root/Desktop

For rename file or directory

#mv dev devops



User Management

For create user account

#useradd shub

For check user account properties

#grep shub/etc/passwd

shub:1001:1001: :/home/shub:/bin/bash

For create user account password

#passwd shub

For check user password properties



#grep shub /etc/shadow

shub:@s$!1bce25f%:18002:0:99999:

 

For switch user account

#su shub

For logout from user account

#exit

Or

Press “ctrl+d” Key

For Delete user account

#userdel shub

For change user Login name

#usermod -l devops shub



Group Management

+ Group is collection of user accounts which is very use full to

administrator for manage and apply permission on number of

users.

For add Group account

#groupadd ibmgrp

For check group account property

#grep ibmgrp /etc/group

Ibmgrp:x:1001:ajay,vijay,sachin

For check group admin property

grep ibmgrp /etc/gshadow



Ibmgrp:!::

For Delete group Account

#groupdel ibmgrp

For add single member in group

#gpasswd -a ajay ibmgrp

For add multiple member in group

#gpasswd -M rahul virat,rohit ibmgrp

For remove group member

#gpasswd -d virat ibmgrp

For make group admin

#gpasswd -A sachin ibmgrp



Linux File System Permission

‘Type of File Permission

Basic Permission

Special Permission

Access Control List (ACL) Permission

For check file permission

#ls -1 /notes.txt

-rw-r—r—. 1 root root 0 Jan 4 14:59 /notes.txt

Permission

Link

Owner

Group owner

Size of file



Date & time of file creation

Name of file

For check directory permission

#ls -Id /dev

Permission in details

File type Permission classes 

d           user   group other

          rwx     rwx   rwx  

r - read

w - write

x - execute

——————

Permission Group

Permission Description

Owner (u) > Permissions used for the owner of the file

Group (g) > Permissions used by members of the group

Other (0) > Permissions used by all other users

For change permission

For add read permission to owner

#chmod utr /notes.txt

For add read write permission to group

#chmod gtrw /notes.txt

For remove read permission to others

#chmod o-r /notes.txt

For change ownership

Syntax:

#chown <user name> <file/directory name>

eg.

#chown ajay /notes.txt

For change group ownership

Syntax:

#chgrp <group name> <file/directory name>

eg.

#chgrp ibmgrp /notes.txt

Set permission with numeric value

r (read) =4

w (write) =2

x (execute) = 1



For set permission with numeric value

#chmod 751 /shub

Access Control List (ACL)

+ Access control list (ACL) provides an additional, more

flexible permission mechanism for file systems.

+ Access control list is service which is use for providing

special permission to specific user and group to

particular directories and file

Use of ACL

Think of a scenario in which a particular user is not a member of

group created by you but still you want to give some read or write

access, how can you do it without making user a member of group,

here comes in picture Access Control Lists, ACL helps us to do this

trick.

For check ACL Permission

Syntax:

#getfacl <name of file or directory>

eg. #getfacl /devops

For set ACL permission to user

#setfacl -m u:shub:rwx /de

For remove ACL permission of user

#setfacl -x u:shub: /devops

For set ACL permission to Group

#setfacl -m g:shubgrp:rwx /devops

For remove ACL permisssion of group

#setfacl -x g:shubgrp: /devops



For remove all ACL permisssions

#setfacl -b /devops

Regular Expressions

What is Regular Expressions?

Regular expressions are special characters which

help search data, matching complex patterns.

GREP (Global Regular Expression Print)

The grep filter searches a file for a particular pattern

of characters, and displays all lines that contain that

pattern.

1. Search a word (string in a file)

#grep root /etc/passwd

2. Search a string in multiple files

#grep root /etc/passwd /etc/group



3. Search a string insensitive in file

#grep -i Root /etc/passwd

4, Search a string in all files recursively

#grep -r root /

5. Inverting the string match

#grep -v root /etc/passwd

6. Displaying the string match total line no

#grep -c root /etc/passwd

7. Display the file names that matches the string



#grep -I root /etc/passwd/etc/shadow

8. Display the file names that do not contain the string

#grep -L root /etc/passwad /etc/shadow

9. Displaying the string match line with number

#grep -n root /etc/passwd

10. Display the lines that start with a string

#grep “root /etc/passwd

11. Display the lines that end with a string

#grep /bin/bash$ /etc/passwd

12. Search and redirect output in a new file

#grep root /etc/passwd > /mnt/find.txt

Find

The Linux Find Command is one of the most important and

much used command in Linux systems.

Find command used to search and locate list of files and

directories based on conditions you specify for files that match

the arguments.

Find can be used in variety of conditions like you can find files

by permissions, users, groups, file type, date, size and other

possible criteria

1. Find files under Home directory

#find /home -name shub.txt

2. Find files with suid permission

#find /-perm 4755

3. Find files with guid permission



#find /-perm 2644

4. Find files with sticky bit permission

#find /-perm 1755

5. Using Find command based on users

#find /-user root

6. Using Find command based on groups

#find /-group shubgrp

7. Search the file with less than 10MB in a folder

#find /tmp -size -10M.

8. Search the file with more than 10MB in a folder

#find /tmp -size +10M.

WC (Word Count)

The we command is use for the count word and line numbers.



1. Count number of lines

#we -l /ete/passwd

2, Count number of words

#we -w /etc/passwd

head

Head command is used for to display top line of the file.

1. Display top 10 line of the file

#head /etc/passwd

2. Display top specific no line of the file

#head -n 15 /etc/passwd



tail

Tail command is used for to display the bottom

line of the file.

1. Display bottom 10 line of the file

#tail /etc/passwd

2. Display bottom specific line of the file

#tail -n 5 /etc/passwd

Archive File in Linux

Archiving is the process of combining multiple files and

directories (same or different sizes) into one file. Archive

process is very useful for backup and compression size of data

in Linux.

What is Tar

 The Linux “tar” stands for tape archive, which is used by large

number of Linux/Unix system administrators to compress size

or drives backup.

For create archive tar used some compression algorithms Such

as gzip,bz2 and xz

Tar command syntax

#tar <options> <files>

Commonly used options

c-for create

x -for extract

v-for verbose

f -for forcefully

t -for test

z-for gzip

j-for bz2



J -for xz

C -for specific destination

For create a tar archive file

# tar -cvf /mnt/backup.tar /var

For show file size in human readable formate

#du-sh /var

#du -sh /mnt/backup.tar

For extract a tar archive file on default location

#tar -xvf /mnt/backup.tar

For extract a tar archive file on specific location

#tar -xvf /mnt/backup.tar -C /root/Desktop/

For create a tar archive file with compress in size (gzip)

# tar -cvzf /mnt/backup.tar.gz /var

For extract a tar archive file with compress in size (gzip)

#tar -xvjf /mnt/backup.tar.bz2

For create a tar archive file with compress in size (xz)

# tar -cvJf /mnt/backup.tar.xz /var

For extract a tar archive file with compress in size (xz)

#tar -xvjf /mnt/backup.tar.xz



Job Automation

+ Job automation allow us perform task automatically in OS by

using tools.

+ This feature is very useful for administrator to assign task to OS

whenever he is not present or perform daily basis work.

Two type of job automation

1. at—at command is used to execute job only one

time.

2. crontab—Crontab command is use for to execute job multiple

time.

For set job with at command

#date

#at 8:10 AM

at>useradd shub

at>

Ctrl+d (write & quit)

For show pending at job

#atq



For remove at job

#atrm 2

For restrict user from accessing at

#vim /etc/at.deny

Shub (add here user name)

:wq (write&quit)

For start crond service

# systemctl start crond



For enable crond service (Permanent on)

# systemctl enable crond

For set cron jobs

#crontab -e

//

For show cron jobs of current user

# crontab -1

For remove cron jobs

# crontab -r

Or

Go to the crontab file and remove job line

#crontab -e

For set cron job to other user

# crontab -u shub -e

For show cron job other user

# crontab -u shub -1

For restrict user from crond service

#vim /etc/cron.deny



For check crontab log file

#tail -f /var/log/cron

Sudo Command

What is sudo?

sudo (“superuser do”, or “switch user do”) allows a user with

proper permissions to execute a command as another user,

such as the superuser.

 sudo allows a permitted user to execute a command as another

user, according to specifications in the /etc/sudoers file.

Provide sudo privilege to user

For edit configuration file:

# vim /etc/sudoers

root ALL=(ALL) ALL

amir ALL=(ALL) ALL (add this line appro. 101 line)

:wq

Provide sudo privilege to group



For edit configuration file:

# vim /etc/sudoers

%punegrp ALL=(ALL) ALL (line number 108)

:wq

By default all member of punegrp group got sudo privileges

Wheel group

Wheel is a system group which by default have sudo privileges,

if we add any member in that group then that user got sudo

privilege

#grep wheel /etc/group

#useradd shub

#passwd shub

#gpasswd -a shub wheel



By default all member of wheel group got sudo privileges

Sudo without password

For edit configuration file:

# vim /etc/sudoers

amir ALL=(ALL) NOPASSWD: ALL

%punegrp ALL=(ALL) NOPASSWD: ALL

:wq,

Managing networking based on Red Hat Enterprise

Linux

For show ip address

#ifconfig

Or

#ip addr

Configure networking with nmcli



Network Manager is a daemon that monitor and manages network

settings.

nmcli command used to manage networking

Manage IP configuration

For Show all list of connection

#nmcli_ con show

For show active connection

f#nmcli con show --active

For show specific connection

#nmcli con show “citynet”

For show device status

fnmcli dev status



For create new connection with nmcli

fnmcli con add con-name “citynet” ifname ens33 type ethernet

‘ipv4.add 192.168.0.2/24 gw4 192.168.0.1 ip4.dns 192.168.0.1

connection. autoconnect yes ipv4.method manual

For activate new connection

finmcli con up "citynet”

f#nmcli con show-active

For deactivate connection



#nmcli con down citynet

For start new connection and stop old connection

#nmcli connection modify “citynet” connection.autoconnect no

#nmcli connection modify “pune” connection. autoconnect yes

For remove existing connection

#nmcli con delete citynet

For set hostname

#hostnamectl set-hostname it.citynet.com

For show hostname

#hostname



Configuring networking with nmtui

IP address configuration files

All created connections with nmcli and nmtui by default store in

following file

cd /etc/NetworkManager/system-connections/

#ls

Note:

We can also modify connection using above connection file, but it

not

recommended.

If update file, restart NetworkManger service to update ip-

configuration

#systemctl restart NetworkManager