Linux Commands for freshers and experienced

  

Linux Basic Commands

 

1. Basic commands
2. Text handling
3. system administration
4. Text Processing
5. Process Management
6. Archival
7. Network
8. File Systems
9. Advanced Commands

 

 Linux with Devops interview Questions

1.      Basic commands

#mkdir = create folder

#mkdir /foldername = create folder in /

#rmdir = empty folder delete

#rm -rf foldername = delete any folder

#rm filename = delete file

#date = show date

#time = show time

#cd .. = change directory

#pwd = show path

#ls = list directory

#ls -a = show hidden file

#touch = create blank file

#history = show commands history

#history -c = clear commands history #cal = show calander

#cal anyyear = show year calander

#useradd username = add user

#passwd username = set user password

#userdel username = delete user account

#userdel -r username = delete user account with all files

#su - username = login user in terminal

#useradd -s /sbin/nologin username = create user with nologin

#usermod = changes in already create user

#useradd -u 2000 username = create user with any user ID (2000,1500,3000etc.)

#groupadd groupname = create group

#useradd -G groupname username = create user (add in group)

#usermod -G groupname username = user add in group(already create user account)

#usermod -l newname oldname = change user login name

#usermod -c "add comment" username = add comment in user

#cat = show file

#ls -ld /foldername = show folder permission

#chmod 770 /foldername = give permission to folder

4=read

2=write

1=execute

#chgrp groupname /foldername = give group ownership

#vim filename = edit file in terminal

#cp /copyfilelocation /savefilelocation= copy file

example :- cp /etc/fstab /var/tmp

#getfacl filename = show advance permission

#setfacl -m u:username:rwx filename = set advanced permission

r = read

w = write

x = execute

- = give no permission

compresse file #du -sh /filename = show folder size

#tar -cvf newname.tar /foldername = compresse in tar

#bzip2 newname.tar = compresse in bzip2

#gzip newname.tar = compresse in gzip

#xz newname.tar = compresse in xz

 

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2.       Text handling

#mkdir – make directories

Usage: mkdir [OPTION] DIRECTORY...

eg. mkdir soni

2. #ls – list directory contents

Usage: ls [OPTION]... [FILE]...

eg. ls, ls l,

ls prabhat

3.#cd – changes directories

Usage: cd [DIRECTORY]

eg. cd soni

4.#pwd print

name of current working directory

eg. pwd

5.#vim – Vi Improved, a programmers text editor

Usage: vim [OPTION] [file]...

eg. vim file.txt

6.#cp – copy files and directories

Usage: cp [OPTION]... SOURCE DEST

eg. cp sample.txt sample_copy.txt

7.#mv – move (rename) files

Usage: mv [OPTION]... SOURCE DEST

eg. mv old.txt new.txt

8.#rm remove files or directories

Usage: rm [OPTION]... FILE...

eg. rm file1.txt , rm rf

9.#find – search for files in a directory hierarchy

Usage: find [OPTION] [path] [pattern]

eg. find file1.txt, find name

file1.txt

10.#history – prints recently used commands

Usage: history

 

 

         3. system administration

11.#chmod – change file access permissions

Usage: chmod [OPTION] [MODE] [FILE]

eg. chmod 744 calculate.sh12.#chown – change file owner and group

Usage: chown [OPTION]... OWNER[:(GROUP)] FILE...

eg. chown remo myfile.txt

13.#su – change user ID or become superuser

Usage: su [USERNAME] [LOGIN]

eg. su remo, su

14.#passwd – update a user’s authentication tokens(s)

Usage: passwd [USER NAME]

eg. passwd

15.#who – show who is logged on

Usage: who [OPTION]

eg. who , who d

 

 

4.       Text Processing

16.#cat – concatenate files and print on the standard output

Usage: cat [OPTION] [FILE]...

eg. cat file1.txt17.#echo – display a line of text

Usage: echo [OPTION] [string] ...

eg. echo hello friends

18.#grep - print lines matching a pattern

Usage: grep - [OPTION] PATTERN [FILE]...

eg. grep i apple sample.txt

19.#wc - print the number of newlines, words, and bytes in files

Usage: wc - [OPTION]... [FILE]...

eg. wc file1.txt

wc L file1.txt

20.#sort – sort lines of text files

Usage: sort [OPTION]... [FILE]...

eg. sort file1.txt

sort r file1.txt

 

5.       Process Management

21.#ps – report a snapshot of the current processes

Usage: ps [OPTION]

eg. ps, ps el22.#kill – to kill a process(using signal mechanism)

Usage: kill [OPTION] pid

eg. kill 9 2275

23.#bg – make a foreground process to run in background

Usage: type 'ctrl+z' and then 'bg '

24.#fg – to make background process as foreground process

Usage: fg [jobid]

25.#jobs – displays the names and ids of background jobs

Usage: jobs

 

6.        Archival

26.#tar – to archive a file Usage: tar [OPTION] DEST SOURCE

eg. tar cvf

/home/archive.tar /home/original

tar xvf /home/archive.tar27.#zip – package and compress (archive) files

Usage: zip [OPTION] DEST SOURSE

eg. zip original.zip original

28.#unzip – list, test and extract compressed files in a ZIP archive

Usage: unzip filename

eg. unzip original.zip

 

 

 

 

 

7.       Network

29.#ping - ping desktop

eg. ping desktopX.example.com30.#ssh – SSH client (remote login program)

“ssh is a program for logging into a remote machine and for

executing commands on a remote machine”

Usage: ssh [options] [user]@hostname

eg. ssh X guest@10.105.11.20

31.#scp – secure copy (remote file copy program)

“scp copies files between hosts on a network”

Usage: scp [options] [[user]@host1:file1] [[user]@host2:file2]

eg. scp file1.txt guest@10.105.11.20:~/Desktop/

 

 

8.       File Systems

32.#fdisk – partition manipulator

eg. sudo fdisk -l33.#mount – mount a file system

Usage: mount -t type device dir

eg. mount /dev/sda5 /media/target

34.#umount – unmount file systems

Usage: umount [OPTIONS] dir | device...

eg. umount /media/target

35.#du – estimate file space usage

Usage: du [OPTION]... [FILE]...

eg. du

36.#df – report filesystem disk space usage

eg. df -h

37.#quota – display disk usage and limits

Usage: quota [OPTION]

eg. quota v

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9.      Advanced Commands

38.#reboot – reboot the system

Usage: reboot [OPTION]

eg. reboot39.#poweroff – power off the system

Usage: poweroff [OPTION]

eg. poweroff

40.#sed stream

editor for filtering and transforming text

Usage: sed [OPTION] [inputfile]...

eg. sed 's/love/hate/g' loveletter.txt

41.#awk pattern

scanning and processing language

eg. awk F: '{ print $1 }' sample_awk.txt

42.#locate – find or locate a file

Usage: locate [OPTION]... FILE...

eg. locate file1.txt