command.md

ls - list the files and directories in the current directory

ls

cd - change the current directory

cd dir_name

mkdir - create a new directory

mkdir rohan

rmdir - remove a directory

rmdir rohan

pwd - print the current working directory

pwd

cp - copy files or directories

We will copy a file called example.txt from the current directory to a directory called backup

cp example.txt backup/

mv - move or rename files or directories

mv example.txt backup/

rm - remove files or directories

rm example.txt

touch - create a new empty file or update the timestamp of an existing file

touch shayan.txt

cat - concatenate and display files

cat example.txt

man - manual for a command

man ls

htop - an interactive process viewer and system monitor

htop

chmod - change the permissions of a file or directory

The first digit represents the owner of the file/directory

The second digit represents the group that the file/directory belongs to

The third digit represents all other users

0 (no permission)

1 (execute only)

2 (write only)

3 (write and execute)

4 (read only)

5 (read and execute)

6 (read and write)

7 (read, write, and execute)

chmod 700 file.txt

chown - change the owner of a file or directory

chown new_owner example.txt

tar - create or extract compressed archive files

x: extract files from an archive

t: list the contents of an archive

r: append files to an existing archive

z: use gzip compression

j: use bzip2 compression

cf: create file

xf: extract file

tar cf archive.tar file1 file2 file3

gzip - compress files

gzip file.txt

gunzip - decompress compressed files

gunzip file.txt.gz

ssh - connect to a remote server securely

ssh username@server_address

scp - securely copy files between systems

scp myfile.txt user@remotehost:/home/user/

ping - test network connectivity

ping 8.8.8.8

ifconfig - display or configure network interfaces

ifconfig

netstat - display network connection information

netstat

route - view or configure network routing tables

route [options] [add/delete/show]

top - display system resource usage and processes

top

ps - display information about running processes

ps aux

kill - terminate a process

kill [PID]

systemctl - control system services and settings

Start the nginx service

systemctl start nginx

Check the status of the nginx service

systemctl status nginx

Stop the nginx service

systemctl stop nginx

service - control system services

service apache2 start

useradd - add a new user to the system

useradd harry

passwd - change the password for a user

passwd harry

userdel - delete a user from the system

userdel harry

su - switch user to become another user

su john

sudo - execute a command as another user or with elevated privileges

sudo

uptime - display system uptime and load average

uptime

df - display disk space usage

df

du - display disk usage by file or directory

du

mount - mount a file system

sudo mount /dev/sdb1 /mnt/usb

umount - unmount a file system

sudo umount /mnt/usb

date - display or set the system date and time

date

whoami - display the current user name

whoami

which - locate a program or command in the system path

which ls

finger - displays all the information about a user

finger harry

uname - display system information

uname uname -a

history - display a list of previously executed commands

history

echo - display text or variables to the console

echo 'I need Tshirt from codeswear!'

tee - redirect output to both a file and the console

ls | tee file.txt

locate - locate any file on the system

locate file.txt

sort - sort lines of text in a file or input

cat file.txt

banana

orange

apple

sort file.txt

apple

banana

orange

uniq - remove duplicate lines from a file or input

cat file.txt

apple

orange

banana

apple

banana

uniq file.txt

apple

orange

banana

head/tail - display the first/last few lines of a file or input

display first 10 lines

head file.txt

display last 10 lines

tail file.txt