linux-commands-cheat-sheet

The cheat-sheet

This cheat sheet is based on the book "Linux Basics for Hackers" by OccupyTheWeb.

Please note that this cheat sheet is not intended to replace the book in any way. It serves simply as a reminder of the most commonly used commands. It does not provide exhaustive details of each command. For more in-depth information, I recommend using the man command or --help option to learn about each command. The book provides detailed explanations of each command with examples, which I strongly recommend exploring. You can find it on Amazon and their website: Amazon Link Website Link

Basic Commands

Command	Description	Example Usage
pwd	Prints the current working directory.	pwd
whoami	Displays the current username.	whoami
cd	Changes the current directory.	cd /path/to/directory
ls	Lists directory contents.	ls -la
--help	Displays help information for a command.	ls --help
man	Shows the manual for a command.	man ls
locate	Finds files by name.	locate filename
find	Searches for files in a directory hierarchy.	find /path -name filename
which	Shows the path of a command.	which ls
ps	Displays information about running processes.	ps aux
cat	Concatenates and displays file contents.	cat file.txt
mkdir	Creates a new directory.	mkdir new_directory
rm	Removes files or directories.	rm file.txt rm -rf directory_name
rmdir	Removes empty directories.	rmdir empty_directory
mv	Moves or renames files or directories.	mv oldname.txt newname.txt
touch	Changes file timestamps or creates an empty file.	touch newfile.txt

Text Manipulation

Command	Description	Example Usage
cat	Concatenates and displays file contents.	cat file.txt
head	Outputs the first part of files.	head -n 10 file.txt
tail	Outputs the last part of files.	tail -n 10 file.txt
nl	Numbers lines of files.	nl file.txt
sed	Stream editor for filtering and transforming text.	sed 's/old/new/g' file.txt
more	View file contents one screen at a time.	more file.txt
less	Similar to more, but with backward movement.	less file.txt

System Management Commands

Command	Description	Example Usage
ps	Displays information about running processes.	ps
ps aux	Displays detailed information about all running processes.	ps aux
nice	Runs a command with modified scheduling priority.	nice -n 10 command
kill	Sends a signal to terminate a process.	kill 1234
killall	Kills processes by name.	killall firefox
fg	Brings a background job to the foreground.	fg %1
at	Schedules commands to run at a later time.	echo "command" | at 10:00
chown	Changes file ownership.	chown user:group file.txt
chmod	Changes file permissions.	chmod 755 file.txt

Add or Install Software Commands

Command	Description	Example Usage
apt	Package handling utility for Debian-based systems.	apt update
apt-get	APT package handling utility.	apt-get install package_name

Network Commands

Command	Description	Example Usage
ifconfig	Configures network interfaces.	ifconfig eth0
iwconfig	Configures wireless network interfaces.	iwconfig wlan0
dhclient	Dynamic Host Configuration Protocol Client.	dhclient eth0
dig	DNS lookup utility.	dig example.com
iwlist wlan0 scan	Scans for available wireless networks.	iwlist wlan0 scan
nmcli dev wifi	Lists available Wi-Fi networks.	nmcli dev wifi
nmcli dev wifi connect some-network password somePassword	Connects to a Wi-Fi network using nmcli.	nmcli dev wifi connect MyWiFi password MyPassword
airmon-ng	WLAN monitor mode enabling tool.	airmon-ng start wlan0
airmon-ng start wlan0	Puts interface wlan0 into monitor mode.	airmon-ng start wlan0
airodump-ng wlan0	Captures raw 802.11 frames.	airodump-ng wlan0
aireplay-ng	Packet injection tool for 802.11 networks.	aireplay-ng -0 5 -a 00:11:22:33:44:55 wlan0
aircrack-ng	802.11 WEP and WPA-PSK keys cracking program.	aircrack-ng -w wordlist.txt captured.cap
hcitool	Configures Bluetooth connections.	hcitool scan

802.11

User Environment Variable Management Commands

Command	Description	Example Usage
env	Displays the current environment variables.	env
set | more	Displays all shell variables and functions, paginated.	set | more
HISTSIZE	Sets the number of commands to remember in the command history.	HISTSIZE=1000
echo $HISTSIZE	Displays the current value of the HISTSIZE variable.	echo $HISTSIZE
export	Sets environment variables or marks shell variables for export.	export VAR=value
export HISTSIZE	Exports the HISTSIZE variable to the environment.	export HISTSIZE=1000
echo $PATH	Displays the current value of the PATH variable.	echo $PATH
someNewVariable="Some value"	Sets a new shell variable.	someNewVariable="Some value"
echo $someNewVariable	Displays the value of someNewVariable.	echo $someNewVariable
unset someNewVariable	Removes someNewVariable from the shell environment.	unset someNewVariable

Compressing and Decompressing Commands

Command	Description	Example Usage
tar	Creates an archive from a list of files.	tar cvf archive.tar file1 file2
tar -rvf	Appends files to an existing archive.	tar -rvf archive.tar newfile
tar -xvf	Extracts files from an archive.	tar -xvf archive.tar
tar -xf	Extracts files from an archive without verbose output.	tar -xf archive.tar
gzip	Compresses files using gzip.	gzip file.txt
bzip2	Compresses files using bzip2.	bzip2 file.txt
compress	Compresses files using the compress program.	compress file.txt
uncompress	Decompresses files compressed by the compress program.	uncompress file.txt.Z

Mounting and Unmounting Commands

Command	Description	Example Usage
mount	Mounts a filesystem.	mount /dev/sdb1 /mnt
umount	Unmounts a filesystem.	umount /mnt
fsck	Checks and repairs a filesystem.	fsck /dev/sdb1
df	Reports file system disk space usage.	df -h

Service and Database Commands

Command	Description	Example Usage
service	Controls system services.	service apache2 start
show databases	Lists all databases in a DBMS.	show databases (MySQL)
use mysql	Switches to the MySQL system database.	use mysql
use somedatabase	Switches to a specific database in DBMS.	use somedatabase (MySQL)
show tables	Lists tables in the current database.	show tables (MySQL)
describe sometable	Shows the structure of a table.	describe sometable (MySQL)
su postgres	Switches user to postgres (switch user).	su postgres
db_status	Checks the status of a database (generic).	db_status

Network Tracing and Proxy Commands

Command	Description	Example Usage
traceroute www.shanick.dev	Traces the route packets take to a network host.	traceroute www.shanick.dev
proxychains	Forces any TCP connection made by any given application through a proxy.	proxychains command
proxychains nmap	Uses nmap with proxychains to scan a host through a proxy.	proxychains nmap -sV -T5 10.19.15.2
cat /etc/proxychains.conf	Displays the content of /etc/proxychains.conf using cat.	cat /etc/proxychains.conf
proxychains firefox www.shanick.dev	Opens Firefox and forces it to use a proxy specified in proxychains.conf.	proxychains firefox www.shanick.dev

System Information and Kernel Commands

Command	Description	Example Usage
uname -a	Displays system information including kernel version.	uname -a
cat /proc/version	Displays Linux kernel version information.	cat /proc/version
sysctl -a | less	Displays kernel parameters and their values interactively.	sysctl -a | less
lsmod	Lists loaded kernel modules.	lsmod
modprobe -a <module name>	Loads specified kernel module(s).	modprobe -a usb-storage
modprobe -r <module to delete>	Unloads specified kernel module.	modprobe -r usb-storage
dmesg	Displays kernel ring buffer messages.	dmesg

Scheduling Tasks and Service Management

Command	Description	Example Usage
crontab -e	Edits the user's crontab file to schedule tasks.	crontab -e
update-rc.d	Updates the System V init links for service control scripts.	update-rc.d apache2 defaults
rrconf	Manages configuration for RunRev scripts.	rrconf list

• 0 8 * * 1 /path/to/command
• 0 indicates the minute (in this case, 0).
• 8 indicates the hour (in this case, 8 AM).
• * * indicates that the task will run any day of the month and any month.
• 1 indicates that the task will run every Monday (Monday is day 1 of the week in cron).
• /path/to/command is the path to the command that will be executed.

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Pull requests are welcome for adding or removing commands, as well as for modifying or correcting errors.