Linux Commands 101

Linux Commands 101

Cloud Maestro
·May 15, 2021·

8 min read

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adduser/addgroup

Allows us to add users and groups to the system

agetty

A program which manages physical or virtual terminals and is invoked by init. When it detects a connection, it opens a tty port, asks for a user’s login name and calls up the /bin/login command.

alias

Creates aliases to a Linux command. Its temporary for a session, you can make it permanent by adding them to ~/.bashrc file.

anacron

Used to run commands periodically with a frequency defined in days, weeks and months (Similar to CRON where CRON is appropriate for servers and ACRON is for desktop/laptop machines).

Remember: CRON is a daemon where anacron is not a daemon

apropos

Used to search and display a short man page description of a command/program.

apt

A higher-level package manager.

apt-get

A Front-end package manager.

aptitude

A powerful text-based interface to the package management system.

arch

Displays machine architecture or hardware name.

arp

Maps IP network addresses of a network neighbor with the hardware (MAC) addresses in an IPv4 network.

at [An alternative to cron and anacron]

Schedule tasks to run in a future time.

atq

View jobs in at command queue.

atrm

Used to remove/deletes at command jobs.

awk

A powerful programming language created for text processing and generally used as a data extraction and reporting tool.

batch

Used to schedule tasks to run a future time, similar to the at command.

basename

Prints the name of a file stripping of directories in the absolute path.

bc

Powerful and Arbitrary Precision CLI Calculator.

bg

Sends a process to the background.

bzip2

Used to compress or decompress a file.

cal

Prints the Calendar.

chrgrp

Changes the group ownership of a file.

chmod

Changes File access permissions.

chown

Changes the user/group ownership of a file.

cksum

Display the CRC checksum and byte count of an input file.

clear

Clears the Terminal.

cmp

Compares between bytes of two files.

comm

Compares to two sorted files line-by-line.

cp

Used to Copy files and folders.

date

Displays the system date and time.

dd

Used for copying files, converting and formatting according to flags provided.

df

Shows file system disk space usage.

diff

Compare two files line by line.

dir

Lists the contents of the directory.

dmidecode

A tool for retrieving hardware information of any Linux system.

du

Show disk space usage of files present in a directory as well as its sub-directories.

echo

Prints a text of line provided to it.

eject

Ejects removable media such as DVD/CD ROM or floppy disk from the system.

env

Lists all the current environment variables and used to set them as well.

exit

Used to exit a Shell.

expr

Used to calculate an expression.

factor

Shows the Prime factors of the number.

find

Search for files in a directory as well as its sub-directories.

free

Shows the system memory usage.

grep

Searches for a specified pattern in a file or files.

group

Displays all the names of groups a user is a part of.

Gzip

Helps to compress a file, replaces it with one having a .gz extension.

Gunzip

Expands or restores files compressed with gzip command.

Shows first lines (10 lines by default) of the specified file or stdin to the screen.

history

Shows previously used commands or to get info about command executed by a user.

hostname

Used to print or set system hostname in Linux.

hostnamectl

Used to print or modify the system hostname and any related settings.

hwclock

A tool for managing the system hardware clock; read or set the hardware clock.

hwinfo

Used to probe for the hardware present in a Linux system.

id

Shows user and group information for the current user or specified username.

ifconfig

Used to configure a systems network interfaces.

ionice

Used to set or view process I/O scheduling class and priority of the specified process.

iostat

Used to show CPU and input/output statistics for devices and partitions.

ip

Used to display or manage routing, devices, policy routing and tunnels.

iptables

For managing incoming and outgoing traffic via a set of configurable table rules.

iw

Used to manage wireless devices and their configuration.

iwlist

Displays detailed wireless information from a wireless interface.

kill

Used to kill a process using its PID by sending a signal to it.

killall

Used to kill a process by its name.

kmod

Used to manage Linux kernel modules.

last

Displays a listing of last logged in users.

ln

Used to create a soft link between files.

locate

Used to find a file by name.

login

Used to create a new session with the system.

ls

Used to list contents of a directory.

lshw

A minimal tool to get detailed information on the hardware configuration of the machine.

Remember: Invoke it with superuser privileges to get a comprehensive information.

lscpu

Displays system’s CPU architecture information.

lsof

Displays information related to files opened by processes.

lsusb

Shows information about USB buses in the system and the devices connected to them.

man

Used to view the on-line reference manual pages for commands/programs.

md5sum

Used to compute and print the MD5 message digest of a file.

Remember: If run without arguments, debsums checks every file on your system against the stock md5sum files

mkdir

Creates one or more folders.

more

Enables you to view through relatively lengthy text files one screenful at a time.

mv

Used to move a file or folder and also used to rename a file or folder.

nano

A Small and Friendly Text Editor

nc (or) netcat

Used for performing any operation relating to TCP, UDP, or UNIX-domain sockets.

netstat

Displays useful information concerning the Linux networking subsystem like

  • network connections,
  • routing tables,
  • interface statistics,
  • masquerade connections,
  • and multicast memberships.

nice

Used to show or change the nice value of a running program.

nmap

A popular and powerful open source tool for network scanning and security auditing.

nproc

Shows the number of processing units present to the current process.

openssl

A command line tool for using the different cryptography operations of OpenSSL’s crypto library from the shell.

passwd

Used to create/update passwords.

pid

Displays the process ID of a running program/command.

ping

Used to determine connectivity between hosts on a network.

ps

Shows useful information about active processes running on a system.

pstree

Displays running processes as a tree which is rooted at either PID or init if PID is omitted.

pwd

Displays the name of current/working directory.

rdiff

A powerful local/remote incremental backup script written in Python.

reboot

Used to halt, power-off or reboot a system.

rename

Used to rename many files at once.

rm

Used to remove files or directories.

rmdir

Helps to delete/remove empty directories.

scp

Enables you to securely copy files between hosts on a network.

shutdown

Schedules a time for the system to be powered down.

sleep

Used to delay or pause.

sort

Used to sort lines of text in the specified file(s) or from stdin.

split

Used to split a large file into small parts.

ssh

An application for remotely accessing and running commands on a remote machine.

stat

Used to show a file or file system status.

su

Used to switch to another user ID or become root during a login session.

sudo

Allows a permitted system user to run a command as root or another user.

sum

Used to show the checksum and block counts for each each specified file on the command line.

tac

Concatenates and displays files in reverse.

tail

Used to display the last lines (10 lines by default) of each file to standard output.

talk

Used to talk to another system/network user.

tar

A most powerful utility for archiving files.

tee

Used to read from standard input and prints to standard output.

tree

A tiny, cross-platform command-line program used to recursively list or display the content of a directory in a tree-like format.

time

Runs programs and summarizes system resource usage.

top

Displays all processes on a Linux system in regards to memory and CPU usage and provides a dynamic real-time view of a running system.

touch

Changes file timestamps

tr

A useful utility used to translate or delete characters from stdin, and write the result to stdout or send to a file.

uname

Displays system information such as operating system, network node hostname kernel name, version and release etc.

uniq

Displays or omits repeated lines from input.

uptime

Shows how long the system has been running.

users

Shows the user names of users currently logged in to the current host.

vim

Used to edit all kinds of plain text and program files.

w

Displays system uptime, load averages and information about the users currently on the machine, and what they are doing.

wall

Used to send/display a message to all users on the system.

watch

Runs a program repeatedly while displaying its output on fullscreen.

wc

Used to display newline, word, and byte counts for each file specified, and a total for many files.

wget

A simple utility used to download files from the Web in a non-interactive way.

whatis

Searches and shows a short or one-line manual page descriptions of the provided command name

which

Displays the absolute path of the files which would be executed in the current environment.

who

Shows information about users who are currently logged in.

whereis

Helps us locate the binary, source and manual files for commands.

xargs

A useful utility for reading items from the standard input, delimited by blanks or newlines, and executes the entered command.

yes

Used to display a string repeatedly until when terminated or killed.

zcmp and zdiff

A minimal utilities used to compare compressed files.

zip

A simple and easy-to-use utility used to package and compress files.

zz

Offers quick access to files and directories

and there more commands. Comment Below the commands that are left out...😉


Reference : tecmint.com

 
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