DevOps: Linux.....!

Linux

====================================

Linux is started around 1991 by Linus Torvalds.
Open Source
Linux is a multi-user & multi-tasking OS.
Linux is "Case-sensitive".

Linux distributions :

Redhat
Centos
Ubuntu
SusLinuxux
Mandriva
Ferodo
Debian
Gentoo
Slackware

Linux File Structure:

home: Users' information

Reddy
Rama
Lakshmi
Krishna

bin: Contains of binary files (ls,mkdir,cd....etc)

                 sbin: System-bin (Contains of binary files)
     bin:  Normal Users can access
   sbin, bin: Root user can access

Types of users:

Admin User--Super User--Root User
Normal User
System User---------[After installing the packages System user will create them automatically]

etc: All configuration files ---------------------------------[ password,shadow,group & sshd_Config ]

lib:

Proc: Process information ----------------------------------------------------------[ meminfo, cpuinfo ]

opt:

By default empty.
3rd-party packages installed here.

temp: It can be accessed by any user

dev: Contains all devices information -----------------[ Printer info, Scanner machine info.......etc..! ]

How to know which version we are using?

cat /etc/release

Basic Commands

mkdir <dir_name> ------------> empty dir only

mkdir -v <dir_name> (-v -----Verbos)----(display a message)..

mkdir -vp <dir_name> <dir_name> <dir_name> <dir_name> (-p -----parent)

mkdir -m 700 <File_name>

rm -rf <dir_name>----------------------------> non-empty dir r ----Recursive

rm-f <File_name>----------------------------> Files only f ----Forcefully

ls -l---------------------------> long listing
ls -la--------------------------> hidden files also
ls -lt--------------------------> last access time (top) l ---- Long list
ls -ltr-------------------------> last access time (down) t ---- Access time
ls -lh-------------------------> Human readable format r ---- Reverse
ls -li--------------------------> display the inode number
pwd--------------------------> print working dir
tree

touch <File_name>--------> create a empty file / time stamp

   cd------------------------------> Change directory
   cd .. ---------------------------> One level up
   cd ../.. -------------------------> Two levels up
   cd ../../.. -----------------------> Three level up
   cd ~ (Tilt symbol)-------------> User home directory
   cd - (ifen symbol)-------------> goto previous working dir.

File Maintenance Commands

find . -type -f all the Two files in the current dir [. current dir]
find . -type -f -empty all empty files
find ~ -type -f -empty all empty files on user HD
#find / -type -f -empty Empty files in entire server
find . -type -d Find dire in current dir
find . -name "devops"
find . -empty

find . -type - -empty empty dir
find ~ -type -f -empty all dir on user HD
#find / -type -f -empty entire server find dir

umask default_dir default_File

root 0022 755 644
Normal_user 0002 775 664

===============================================

Base premission for dir 0777 0666

0022 0022

755 644

Base permission for file 0777 0666

0002 0002

775 664

r------read---------->4
w-----write--------->2
x------execute------>1

7 5 5
| | |
| | Other (0)
| Group (g)
Owner/group (u)

chmod

Change mode
Change the permission for files or dir

syntax:- chmod <Permission> <Dir/file_name>

chmod 000 devops.txt / chmod ugo-rwx devops.txt
chmod 444 devops.txt
chmod 744 devops.txt
chmod -R 777 devops----------[Change the permission all sub-dir also.] [ -R-------recursive]

chmod +r devops.txt ----- set read permission to ugo
chmod ugo+r devops.txt ----- same as above
chmod ugo+x devops.txt
chmod ugo+w devops.txt
chmod u+rwx, g+r, o+x devops.txt

chown

Change Owner
If you want to change owner, you must have to switch root users.
sudo su -

Syntax :- chown <User_name> <File_name>

chgrp

Syntax :- chgrp <Group_name> <File_name> [ default group--wheel]

chown <User_name> : <Group_name> <File_name>
chown reddy : testgrp devops.txt

chown -R root devlops/ [ Change the owner for dir ]

cp: Copy

Copy files/dir one location to another location.

cp <file/dir_name> <Destination_dir>
cp devops.txt Devops/
cp devops.txt /temp
cp devops.txt /etc
.
cp -r python Devops/ [if you want to copy the directory mentioned(-r)]
cp -r python /temp

mv: Move/ Rename

If you wan to rename the file/directory.

mv <Old_name> <New_name>
mv devops/ azure /
mv devops.txt azure.txt

If you want to Move the file/directory.

mv <Source> <Destination>

file <Provide file path here>

with help of this command you can able to know what type of file it is, you can find below ex.,
ASCII test
Empty file
block special

mv: Word Count

wc -l <File_name> Only line number
wc -w <File_name> Only word number
wc -c <File_name> Only character count number
wc <File_name> it will display the line number

ln:

link
It will create the link b/w files

Hard-Link:

What are the permission have origional file same link (ln) file also have.
Inode also same in Hard link
But we could not able to find which file is origional in between two link (ln) file.
The file size same in both (Origional file & Hard link file also)

5 GB
ln /opt/flipkart/flipkart.log /tmp/flipkart_ln_file.txt
5 GB

Soft-Link:

The link number it will not change when you create a Soft-link.
The file starting with (L) means Soft-link.
The link file and origional file size will be different
Once you delete the origional file, the Soft-link can't able to access.
The inode will be different to origional and Soft-link

5 GB
ln -s /opt/flipkart/flipkart.log /tmp/flipkart_ln_file.txt
5 KB

Editor:

yum install vim -y
:se nu
:se nonu
/<Serch_here>
:<line_number> [ jump to the particular line numner ]
dd

Text Reading/Display Commands

echo Hello Hi
echo Hello Hi
echo "Hello Hi"
echo 'Hello Hi'

cat <File_name> [ display the content ]
cat -n <File_name> [ along with line number ]

head <File_name> [ display First 10 lines ]

head -n 25 <File_name> [ display First 25 lines ]

head -25 <File_name>

tail <File_name> [ display last 10 lines ]
tail -25 <File_name> [ display last 25 lines ]
tail -n 25 <File_name>
tail -f <File_name> [ it will keep on display last 10 lines ] ***********
-f ---- file appending

sed -n "<line_number>p" <File_name>

sed -n "123p" devops.txt---------------------------------------------> it will print particular numer content only.

sed -n "123,130p" devops.txt---------------------------------------> print from 123 to 130 lines.

How to replace the content in file

sample.txt

red is danger color red red

red red red red

red red red

red red

red

I want to replace red into blue

sed 's/red/blue/' sample.txt ---it will replace first word of the each line (For Temparary).
sed 's/red/blue/2' sample.txt ---it will replace second word of the each line. (For Temparary)
sed 's/red/blue/g' sample.txt ---done (For Temparary)
s------------String
g -----------globel
sed =
S --- String
ed --- Editor

sed -i 's/red/blue/g' sample.txt ******

How to display page by page /screen by screen

more <File_name> ------------------> we can print the forward only.
more <File_name>-------------------> we can forward and backword.

ctrl + f----------------> forward
ctrl + b---------------->backward
Enter-----------------> line by line

--------------------------------------------------------------------------------------------------------------------------------------------------

| pipe:-

Pipe is a temporary momory location.
where we can store the one command In-put & give same as Out-put to other command.

cat <File_name> | sort
cat <File_name> |sort -r
cat <File_name> |sort | tr [a-z] [A-Z]

-----------------------------------------------------------------------------------------------------------------------------------------------

grep: *********************

Global Regular Expression Print

grep <What_You_want_to_Serch > <Where_you_want_to_serch>

grep reddy sample.txt

grep -i reddy sample.txt [ -i ---- ignoring the case sentitave ]

grep -i 'Reddy Sekhar' sample.txt

===========================================================

System Resources Commands:

============================================================

who ---------------------------------------> How many users are loged in currently.

who -H------------------------------------> with Heading it will display.

w-------------------------------------------> display more information about user,

How many users are logedin,

What they are doing.

How long the server is up and running.

display load average.(How your CPU performing).

0.00, 0.00, 0.00

1st minute 5th minute 15th minute

If it is more than cpu count it will indicate cpu utilization is very high.

it is based on no.of core (CPU).

How to know my ststem cpu(Core_info) infomaton.

----------------------------------------------------------------

cat /proc/cpuinfo

uptime------------------------------------->it will display when it is re-started.

users---------------------------------------->

whoami------------------------------------> Currently which user logedin.

whereis <Cmd>---------------------------> print manual pages info

whereis ls binary file path info.

whereis java

whereis mkdir

last ---------------------------------------> how many user login & how much time they spend it.

from which ip address he loged in.

date

date -s "enter date here"------------------> as a root user we can set the date.

df ------disk free---------------------------->to find how many hard disk are attached to linux system

Each hard dist how much is accupaid.

remain how much free space we have.

du -h ~ -------------------------------------> user home dir how much space accupaid.

du -sh ~-------------------------------------> it will display summery only.

hostname -i ------------------------------> |

ifconfig--------------------------------------> display IP address |--------------------------------------> dispaly ip address

ip a ------------------------------------------> |

hostname----------------------------------->

man ls

man mkdir

man cd

whereis mkdir

whereis ls

whereis cd -----------------------> it will display manual pages.

dispaly Binary path

info mkdir

info ls

info cd

mkdir --help

cd --help

ls --help

whatis ls

whatis mkdir

whatis cd------------------------> Short discription.

-----------------------------------------------------------------------------------------------------------------------------------

How to find services on your system:

---------------------------------------------

services.msc----------------------> display all running services on windows machine

syatemctl list-unit-files--------> For linux

systax: service <Service_name> <Options>

-------- <stop>

<start>

service sshd status

service sshd start

service sshd stop

service sshd restart

systemctl <Option> <Service_name>

systemctl start sshd.service

systemctl stop sshd

systemctl status sshd

systemctl restart sshd

--------------------------------------------------------------------------------------------------------------------------------

===========================================================

Process Management Commands

============================================================

ps -----------------------------> display current user process id information

ps -ef | grep java--------- -> display java process only

ps -ef | grep jenkins

ps -ef -------------------------> all the user process id information. (system user information also it will display)

e---------> all

f---------> formated way

----------------------------------------------------------------------------------------------------------------------------------------------

Kill Command:

------------------

-1

-2

-3

kill -4 <Process_ID>

-5

-6

-64

----------------------------------------------------------------------------------------------------------------------------------------------

Archive /Data Backup Commands

--------------------------------------------

zip -r devops.zip DevOps/----------------------------> Create a zip file.

unzip <zip_file_name>

unzip <zip_file_name> -d /temp/------------------> where you wan to extract (Specfic location)

tar -cvf devops.txt DevOps/--------------------------> Create a tar file.

tar -xvf devops.txt

useradd <User_Name>

shadow--------------------. password information will be saved here.

passwd

group

#passwd root

#passwd ec2-user

#passwd ramadevi

Set attributes for your passwd

---------------------------------------

chage <User_name>

Create a group

-------------------

Udemy - Linux

====================================

class : 01 [Introduction]

class : 03 [ How to open and close Terminal ]

Window ----ctrl + alt + t--------Open

ctrl + d-----------close

class : 04 [ Our First Commands ]

sudo apt -y install ncal ----------------------------------> Install cal package.

echo Hello
echo echooooooooooooo
cal
cal 2022 ( cal -y )------------------------>
date
Clear ( ctrl + l )----------------------->
history
!12 ------------------------------------->
!!
history -c; history -w
exit / ctrl + d

class : 05 [ Understanding Command Structure ]

echo $PATH
which cal
which echo
which which
cal
cal 2017
cal 12 2017
cal -y ----------------------------------------------->display current year
date
date -u ( date --universal)----------------------->Universal time
date -abcdef
date --longform1 --longform2 --longform3

Command = CommandName -Options Inputs

cal 12 2017

cal -A 1 12 2017
| | |____________Inputs
| |_________Options
|_____ CommandName

cal -B 1 12 2017
cal -A 1 -B 1 12 2017
cal -A =1 -B=1 12 2017
cal --after =1 --before=1 12 2017

class : 06 [ Using the Linux Manual - Part 1 - The Manual's Structure ]

Section Contians

1 User Commands
2 System Cells
3 C Library Functions
4 Device and Special Files
5 File Formats and Conventions
6 Games
7 Miscellaneous
8 System Administration

class : 07 [ Using the Linux Manual - Part 2 - Reading the Man Pages ]

man -k which [ -k Search]
man 1 which
man 6 sol
man which
man lcf
which date cal
which [ -a ] <Something> ...
which [ -a | -f ] <Something> ...

class : 08 [ Using the Linux Manual - Part 3 - Putting it all together ]

man -k "list directory content"
man ls
ls -l
ls -h
help cd / man cd
man pwd / help pwd
help

class : 01

User / Group Administration Commands

Useradd: Creates a new User account.

After creating a user 3 dire will create automatically.

/etc/passwd

shadow

group

passwd: Changs a User's Password.

passwd ramadevi

passwd ec2-user

passwd root

password information saved in shadow dir

passwd

chage ramadevi

Create a group:

to manage the users..........!

groupadd <Group_Name>

groupadd devops

usermod -g <Group_Name> <User_Name>

How to check a user belongs to how many groups ?

id <User_Name>

groups <user_Name>

id ec2-user

id ramadevi

how to check a particular group how many users are there ?

lid -g <Group_Name>

lid -g devops

su-----------------------> Switch user

Normal_User---------Normal_User---------->passwd

Normal_User---------Root_User-------------->passwd

Root_user--------Normal_User---------->no passwd required

su - ramadevi---------Best practic

su ramadevi

su - root

su -

give sudo access

------------------------

vi /etc/sudoers

visudo--------Best practic

ramadevi

useradd ramadevi

sudo useradd ramadevi

ls -l /home

userdel <User_Name>

userdel -r <User_Name>---------------> if you want to delete user dir also from home dire

groupdel <Group_Name>

Remote Access Commands:

How to connect to the server ?

with help of IP address/Host name

Passwd

ssh un@ip

passwd

ssh ramadevi@IP

passwd

ssh/sshd_config

Scp--------------Secure Copy

Youtube -----SCP Command

Before do make sure passworklessauthentication yes

in both server

Syntax: scp fn/dn un@ip/hn:/temp/

scp devops ec2-user@159.28.1.1:/temp/

Want to check Ram size in server

free

free -h

free -k

free -m

free -g

to check Ram hard ware information:

# dmidecode

dmidecode -t 17

dmidecode -t 15

dmidecode -t 1

dmidecode -t 20

Virtual machine-----------------> typr= ram

On premise machine ----------> type = SDRAM

DDR1, DDR2

Automating/Scheduling Tasks Commands

Crontab

With help of crontab we can scheduling our daily jobs.

By default this features can access all the users.

How to restic to access the everyone ?

Create one empty file in /etc/
touch /etc/crown.all
add the user in cron.all file to whom you wan to give the access

crontab -l---------------> display all jobs

crontab -e---------------> edit existing jobs/create a new jobs

crontab -r----------------> delete jobs

crontab -ir

How to see other user Crontab jobs ?

#crontab -l -u ramadevi

Crontab Format

[Minute]---[Hour]---[Day of month]---[Month]------------[Day of week]---[Command/script]

0-59 0-23 1-31 1-12 or jan-dec 0-6 or sun-sat /usr/bin/.sh

How to stop crontab jobs?

Stop mentioned service

crond.service

*/1 * * * * /home/ec2-user/hello.sh > /home/ec2-user/hello.log

*/1 * * * * /home/ec2-user/hello.sh > /home/ec2-user/hello.log 2>&1

*/1 * * * * /home/ec2-user/hello.sh > > /home/ec2-user/hello.log 2>&1

> -------------redirect std o/p

>> -----------appaned std o/p

File descriptors:

-------------------

1 ----------Stand I/p

2 ----------Stand o/p

3 -----------Stand error

script

script ramadevi.txt

cat typescript

script -a typrscript

Labels: Mithun Technologies

DevOps

Wednesday, August 17, 2022

Linux.....!

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