Linux Common Commands and Vi Editor Shortcuts:

 

ls

lists all the contents in the current working directory.

 

ls <path name>

By specifying the path after ls, the content in that path will be displayed.

 

ls –l

lists all the contents along with its owner settings, permissions & time stamp (long format)

 

ls -a

lists all the hidden contents in the specified directory.

 

ls -lrt

list of files in order of recently modified at last.

 

sudo

This command executes only that command with root/ superuser privileges.

 

sudo useradd <username>

Adding a new user

 

sudo passwd <username>

Setting a password for the new user

 

usermod -aG sudo <user_name>

Give root access to the user.

 

sudo userdel <username>

Deleting the user

 

sudo groupadd <groupname>

Adding a new group

 

sudo groupdel <groupname>

Deleting the group

 

sudo usermod -g <groupname> <username>

Adding a user to a primary group

 

cat

This command can read, modify or concatenate text files. It also displays file contents.

 

cat -b

This adds line numbers to non-blank lines.

 

cat -n

This adds line numbers to all lines.

 

cat -s

This squeezes blank lines into one line.

 

cat –E

This shows $ at the end of line.

 

grep

This command searches for a particular string/ word in a text file. This is similar

to “Ctrl+F” but executed via a CLI.

 

grep -i

Returns the results for case insensitive strings.

 

grep -n

Returns the matching strings along with their line number.

 

grep -v

Returns the result of lines not matching the search string.

 

grep -c

Returns the number of lines in which the results matched the search string.

sort

This command sorts the results of a search either alphabetically or numerically. It also sorts files, file contents, and directories.

 

sort -r

the flag returns the results in reverse order.

 

sort -f

the flag does case insensitive sorting

 

sort -n

the flag returns the results as per numerical order.

 

chmod

This command is used to change the access permissions of files and directories.

chmod <permissions of user, group, others> {filename}

 

4 – read permission

2 – write permission

1 – execute permission 

0 – no permission

 

chmod 777 <filename.sh>

Give permission to file

 

ifconfig

ifconfig (interface configuration) command is used to configure the kernel- resident network interfaces. It is used at the boot time to set up the interfaces as necessary. After that, it is usually used when needed during debugging or when you need system tuning. Also, this command is used to assign the IP address and netmask to an interface or to enable or disable a given interface.

 

ifconfig -a

This option is used to display all the interfaces available, even if they are down.

 

ifconfig -s

Display a short list, instead of details.

 

history

history command is used to view the previously executed command. These commands are saved in a history file. In Bash shell history command shows the whole list of the command

 

history 10

To show the limited number of commands that executed previously.

 

ssh-keygen

Use the ssh-keygen command to generate a public/private authentication key pair. Authentication keys allow a user to connect to a remote system without supplying a password. Keys must be generated for each user separately. If you generate key pairs as the root user, only the root can use the keys.

 

ssh-keygen -t rsa

The following example creates the public and private parts of an RSA key.

 

curl

curl is a command-line tool to transfer data to or from a server, using any of the supported protocols (HTTP, FTP, IMAP, POP3, SCP, SFTP, SMTP, TFTP, TELNET,

LDAP or FILE). This tool is preferred for automation since it is designed to work without user interaction. It can transfer multiple files at once.

 

curi -o

saves the downloaded file on the local machine with the name provided in the parameters.

 

apt-get

apt-get is a command-line tool that helps in handling packages in Linux. Its main task is to retrieve the information and packages from the authenticated sources for installation, upgrade and removal of packages along with their dependencies. Here APT stands for the Advanced Packaging Tool

 

apt-get update

This command is used to synchronize the package index files from their sources again. You need to perform an update before you upgrade.

 

ps

Every process in Linux has a unique ID and can be seen using the command ps.

 

sudo ps aux

a=show processes for all users

u=display the process’s user/owner

x=also show processes not attached to a terminal

 

telnet localhost

connect to a remote Linux computer.

run programs remotely and conduct administration.

 

cd

Change directory.

 

mkdir

Make folder or directory.

 

rm <file_name>

Remove file.

 

rm -r <dir_name>

Remove directory dir

 

rm -f <file_name>

Remove file forcefully.

 

rm -rf <dir_name>

Remove directory forcefully.

 

cp fileA fileB

Copy fileA to fileB

 

mv fileA fileB

Move or rename fileA to fileB

 

touch <file_name>

Create file.

 

cat <file_name>

Displays the content of file.

 

more <file_name>

Displays first 10 lines of file.

 

tail <file_name>

Displays last 10 line of file.

 

ping host

Ping host and output result

 

wget file

Download file.

 

top

Display top process.

 

kill pid

Kill process with process id.

 

netstat -r -v

Print network information, routing and connection.

 

df

Shows disk usage.

 

du

Shows directory space usage.

 

date

Shows the current Server date and time.

 

cal

Shows this month calendar.

 

whoami

Show user who is logged in.

 

tar cf file.tar files

create a tar named file.tar containing files.

 

tar xf file.tar

extract the files from file.tar

 

tar czf file.tar.gz files

create a tar with Gzip compression.

 

tar xzf file.tar.gz

extract a tar using Gzip

 

tar cjf file.tar.bz2

create a tar with Bzip2 compression.

 

tar xjf file.tar.bz2

extract a tar using Bzip2

 

gzip file

compresses file and renames it to file.gz

 

gzip -d file.gz

decompresses file.gz back to file

Shortcuts:

 

Ctrl+C – halts the current command.

Ctrl+Z – stops the current command, resume with fg in the foreground or bg in the background.

Ctrl+D – log out of current session, similar to exit.

Ctrl+W – erases one word in the current line.

Ctrl+U – erases the whole line.

Ctrl+R – type to bring up a recent command.

!! – repeats the last command.

exit – log out of current session.

 

 

Linux Commands for Vi Editor:

 

 

:q

Simple exit

 

:w

Save the file but keep it open.

 

:sh

Execute Shell Commands

 

:q!

Exit without save.

 

:wq

Exit by saving.

 

shift + ^

Move cursor at start of line.

 

shift + $

Move cursor at end of line.

 

shift + h

Move cursor at top of screen.

 

shift + L

Move cursor at bottom of screen.

 

shift + A

Insert Text at the end of line.

 

shift + n

Search Next

 

shift + s

Replace entire line.

 

gg

To go in start of file

 

dd

To delete the entire line

 

shift + G

To go in end of file

 

shift + U

Undo all last changes in line.

 

CTRL+d

Move forward 1/2 screen.

 

YP

Copy the current line and paste (Y for copy P for paste)

 

P

Move cursor where u want to put the copied text.

 

:s/pattern/replace/

Syntax for replace old string with new, here word pattern is old string. (Only on the line)

 

:%s/pattern/replace/

Replace at every occurrence.

 

dw

Delete word.

 

shift + d

Delete to end of line.

 

dd

Delete a single line at once.

 

ndd

Delete n numbers of line (n must be integer)

 

/ xyz

To search xyz in opened file

 

Note: These are very beginner level commands. Follow me on LinkedIn to get notifications for Advance DevOps content including real-time projects.