Commands

What it does

Linux

Operating System  - Open source, multiuser&multiprocessing, security

Ubuntu

Distibution of linux                                             Other distributions: centOS, Amazon linux, RHEL

Shell

Terminal                                                                        -lets user executes command                                   -communicates with kernal

kernal

Heart of Linux - connect shell to Hardware

$ Whoami

To see the currently logged-in user

$ touch filename.txt

Create a file 

$ nano filename.txt

open the nano editor

$ vi filename.txt

open the vi editor

$ vim filename.txt

open the vim editor

$ ls

list the files in a current directory

$ls -l

list the file with long details

$ls -a

list all hidden files (files which start with .<filename> are hidden files )

$ls -i

list the files with index no nodes

$ls .sh

list all the files with .sh extension

$ls -al

list all hidden files with details

$ls -d /

list only directories

$ cat <filename>

To display the contents of the file

$ pwd

Present working Directory

$ cd .

Current directory

$ cd ..

Previous directory

$ cd -

Go to the last working directory

$ cd

Go to the home directory

$ echo "Hello"

To print 

$ rm filename.txt

To delete file

$ mkdir LinuxForDevops

To create folder

$ rmdir LinuxForDevops

To delete folder

$ mkdir -p Linux/Shell

To create multiple nested folders

$ cp names.txt Folder1/

To copy names.txt file in Folder Folder1

$ mv devops.txt cloud.txt

To rename a file

$ mv cloud.txt ../gcpcloud.txt

To rename and also move to previous directory

$ find .

To find in current directory

$ find  . -type d

To find only directories

$ find . -type f

To find only files in current directory

$ find . -type f -mmin +2

To find files in current directory which modified in more than 2 min

$ find . -type f -mtime -2

To find files accessed in last 2 days

$ find -name "*.txt"

To find all files with .txt

$ find . -empty

To find empty files

GREP Command

Global Regular Expression Print -To search text in file or system

$grep "Ansible" names.txt

To find text "Ansible" in names.txt file

$ grep -i "Network"

Not case sensitive

$ grep -w "Network"

To find complete "Network" in names.txt file

$ df

Displays the amount of disk space available on the filesystem

$ du

Measures the disk space occupied by files or directories.

$ free

Outputs a summary of RAM usage

$ vmstat

Gives the information about processes, memory, paging, block IO, disk, and CPU scheduling

$ nslookup google.com

To obtain domain name or IP address mapping

$ ifconfig 

To assign an address to a network interface and to configure or display the current network interface configuration information