system_scripts/linux-commands.txt at main · Macheing/system_scripts · GitHub

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Basic Linux Commands Cheat-Sheet

This list includes a bunch of different commands that are useful to know when working with Linux.
Not all of these commands are covered in the videos, so feel free to investigate them on your own.

Managing files and directories

cd directory: 			changes the current working directory to the specified one

pwd: 				prints the current working directory

ls: 				lists the contents of the current directory

ls directory: 			lists the contents of the received directory

ls -l: 				lists the additional information for the contents of the directory

ls -a: 				lists all files, including those hidden

ls -la: 			applies both the -l and the -a flags

mkdir directory: 		creates the directory with the received name

rmdir directory: 		deletes the directory with the received name (if empty)

cp old_name new_name: 		copies old_name into new_name

mv old_name new_name: 		moves old_name into new_name

touch file_name: 		creates an empty file or updates the modified time if it exists

chmod modifiers files: 		changes the permissions for the files according to the provided modifiers;
				we've seen +x to make the file executable

chown user files: 		changes the owner of the files to the given user

chgrp group files: 		changes the group of the files to the given group


Operating with the content of files

cat file: 			shows the content of the file through standard output

wc file: 			counts the amount of characters, words, and lines in the given file;
				can also count the same values of whatever it receives via stdin

file file: 			prints the type of the given file, as recognized by the operating system

head file: 			shows the first 10 lines of the given file

tail file: 			shows the last 10 lines of the given file

less file: 			scrolls through the contents of the given file (press "q" to quit)

sort file: 			sorts the lines of the file alphabetically

cut -dseparator -ffields file: 	for each line in the given file, splits the line according to the given
				separator and prints the given fields (starting from 1)


Additional commands

echo "message": 		prints the message to standard output

date: 				prints the current date

who: 				prints the list of users currently logged into the computer

man command: 			shows the manual page of the given command; manual pages contain a lot of
				information explaining how to use each command (press "q" to quit)

uptime: 			shows how long the computer has been running

free: 				shows the amount of unused memory on the current system


Redirections, Pipes and Signals Managing streams

These are the redirectors that we can use to take control of the streams of our programs

command > file: 		redirects standard output, overwrites file

command >> 			file: redirects standard output, appends to file

command < file: 		redirects standard input from file

command 2> file: 		redirects standard error to file

command1 | command2: 		connects the output of command1 to the input of command2


OS and Monitoring processes

These are some commands that are useful to know in Linux when interacting with processes.
Not all of them are explained in videos, so feel free to investigate them on your own.

ps: 				lists the processes executing in the current terminal for the current user

ps ax: 				lists all processes currently executing for all users

ps e: 				shows the environment for the processes listed

kill PID: 			sends the SIGTERM signal to the process identified by PID

fg: 				causes a job that was stopped or in the background to return to the foreground

bg: 				causes a job that was stopped to go to the background

jobs: 				lists the jobs currently running or stopped

top: 				shows the processes currently using the most CPU time (press "q" to quit)

strace:				shows us all the system calls our program made. System calls are the calls
				that the programs running in our computer make to the running kernel.


Network Commands:		Discriptions:

tcpdump 			tool is a powerful command-line analyzer that captures or "sniffs" TCP/IP packets

ab -n 500 google.com		tool for measuring speed and responsiveness of given website and generates overall stats.

ssh webserver			connects to webserver.

netstat -nlp | grep :80		generates stat for services connected or listening at port 80.

iftop				displays bandwidth usages

nload				displays network usage

nethogs				monitor network traffic bandwidth flows.

vnstat				monitors network Traffic.

bmon				monitors bandwidth and rate estimator.

iperf/iperf3			measures network bandwidth.


Network GUI tools

Zabbix				free open-source bandwidth monitoring application.

Nagios Core 			a free open-source application used for Monitors Systems, Networks and Infrastructure.

Cacti 				a network monitoring tool that uses PHP and runs in a browser window.