linux-2class.txt

Linux:
Giving super user rights:
1) sudo su

Creating files in linux:

2) cat >file1.txt  (press enter)
   Hello world 
   (to exit this file1.txt you should press ctrl d) 

(it will create a file with name file1 with extension txt and 
content hello world)

3) ls    (list ...you should be able to see file1.txt) 

4) cat file1.txt   (to see the content of the file1.txt ) 

5) to clear screen write clear or press ctrl l 

6) cat >>file1.txt 
Hello akshat 
(press ctrl d to exit )   (this will add hello akshat below Hello world in file1.txt)

7) cat file1.txt      (o/p Hello world
                           Hello akshat)

8) Lets say i have two files a.txt and b.txt . Now a.txt has content -> I am learning devops
and b.txt has content -> Linux is first topic . Now i want to concatenate a.txt and
b.txt and create a new file with name all which will have content of both a.txt and b.txt

cat > a.txt
I am learning Devops 
(press ctrl d to exit) 

cat > b.txt
Linux is first topic
(press ctrl d to exit) 

cat a.txt b.txt > all.txt   (here a.txt and b.txt would be concatenated to become all.txt )

ls 

cat all.txt  (you will see o/p : I am learning devops
				 Linux is first topic )

9) Touch command: -> Created the empty file 
	          -> Create multiple files at a time (with a single command) 
 		  -> Change the timestamp (you can see time when the file created, modify time,change time) 
            

10) touch abc.txt   (it will create a file abc.txt without any content (empty file) )

11) ls    (you will see abc.txt)

12) cat abc.txt  (you will see no content because this file is empty) 

13) touch file3 file4.txt file5 file6 file7 file8   (it will create multiple blank files)

14) stat file3   (it will show the timestamp )

15)  Lets say i have created a file with name akshat.txt ...i added content that akshat is teaching 
devops certification . later you want to delete the content of the file ...(empty the file) 

cat > akshat.txt
akshat is teaching devops certification 
(press ctrl d to exit)

now i want to empty the file :

cat akshat.txt   (you will see content: akshat is teaching devops certification )

>akshat.txt       (this command will delete everything in akshat.txt)

cat akshat.txt  (you will see akshat.txt content is deleted ) 


16) Vi editor : text editor   (for example it will create a file for you and open that file so that you can put the content into the file)

vi devops.txt

(the devops.txt file editor will open in front of you )

To start inserting in the file devops.txt press i   (which is insert) 
hello simplilearn,
hope you are doing great .
i am also good. I am leanring devops today

now to save the file :   
(press esc and then) 
:w -> save the file but not quit
:q ->  quit the file but not save 
:wq or :x-> save the file and quit

(to come out of file press esc :wq) 

cat devops.txt 


17) Creating a directory  (it is a folder in which we can create the files) 

mkdir akshat  

(create a directory (folder) with name akshat ) 

cd akshat 

(change directory to akshat ..you will get inside akshat directory) 

pwd     (to see your current working directory use pwd command)  (o/p : /home/ec2-user/akshat)

mkdir a1 a2 a3   (it will create multiple directories for you)

ls   (you will see a1 a2 and a3) 

cd ..     (between cd and .. there should be space )( go back one step ) 

pwd   (o/p: /home/ec2-user) 

###########GOING BACK 2 steps in a directory###

cd akshat 
cd a1
pwd
cd ../..  (you will go back 2 steps)
pwd        

18) copy the file 

cat > c1.txt 
first file
(press ctrl d to exit)

cp c1.txt c2.txt     (c1.txt is the source file and c2.txt woud be the destination file)

(copy the content of c1.txt to c2.txt and also create c2.txt ...)

cat c2.txt   (o/p : first file)

cat c1.txt (o/p : first file)  


19) Lab: Move the file into directory

touch newfile

ls

mkdir newdirectory

Now i want to move this newfile inside the newdirectory which i created

mv newfile newdirectory    (move the newfile which you created above in the newdirectory which you created above)

ls  (you will see that newfile is missing)

cd newdirectory   (change directory to newdirectory)

ls   (you will the newfile is present in the directory which we have created) 

cd ..



20) lab: i want to rename a file and give a new name to that file


touch hellofile.txt

now i want to rename this file to simpli.txt

mv hellofile.txt simpli.txt 

ls 

(you will see that hellofile.txt name is replaced with simpli.txt name) 



21) Hidden files in linux

touch .akshatfile    (whenever you put . in front of any file it would be created as a hidden file)

ls    (you will not see that file ) 

ls -a   (list all the files inc hidden files)

22)  Lets see how we can remove the files and directory in linux  


``````````rmdir  -> this command is used to remove a specidc directory but it should a empty directory without any files in it `````````````

Lab: 

mkdir hellodirectory
ls

rmdir hellodirectory

ls    (the directory woudl be removed)
######

mkdir hellodirectory    (created the hellodirectory)

cd hellodirectory   (get inside the hellodirectory)

touch file1   (create the file1 in hellodirectory)

cd ..   (come out of hellodirectory) 

rmdir hellodirectory  (since this directoty is not empty you will get an error) (o/p: rmdir: failed to remove ‘hellodirectory’: Directory not empty) 

``````````````` rm -rf  -> Remove both the parent and child directory ...it will also remove delete files ....f -> forefully````````


mkdir -p akshatgupta/simpli   (create a directory named akshatgupta and inside that directory another directory(child) is created with name simpli_ 


rm -rf akshatgupta   -> delete the directory as well as sub directory) 

cat > learndevops.txt
learning devops

(press ctrl d to quit)

rm -rf learndevops.txt 

ls   (the file would be removed)

rm -rf hellodirectory   (the directory we created above)

ls 

###### ADD ON COMMANDS #################


23) to check the Operating system you are using in your server

cat /etc/os-release

o/p: NAME="Amazon Linux"
VERSION="2"
ID="amzn"
ID_LIKE="centos rhel fedora"
VERSION_ID="2"
PRETTY_NAME="Amazon Linux 2"
ANSI_COLOR="0;33"
CPE_NAME="cpe:2.3:o:amazon:amazon_linux:2"
HOME_URL="https://amazonlinux.com/"


24) Install a package /software in linux  (you need to be a sudo user to install these packages) 

lets say for example we want to install apache server (httpd )

yum install httpd 

lets say we want to install dockers 

yum install docker 

yum: yellow dog updater . YUM is the primary package management tool for 
installing, updating, removing, and managing software packages in Red Hat Enterprise Linux. 


yum install git 



Lab:

yum install httpd   (it will install the httpd package )

which httpd   (location of httpd)

yum install docker -y (here -y will ensure that everysetting is kept as default it will not ask you is it ok while installing the software) 


yum remove httpd -y   (it will delete the software httpd from your linux machine)

which httpd   (no httpd found)

yum remove docker -y (it will delete the software docker from your linux machine)

yum install docker -y

yum install httpd -y


yum update docker -y   (this will update the docker software in your linux machine) 


yum update -y (this will update my complete linux machine) (ALL THE SOFTWARES IN YOUR LINUX MACHINE WOULD BE UPDATED ) 

yum list installed  (to see all the packages )