Basic Linux Commands

Linux Commands

Linux command‑line tools are the backbone of reconnaissance, exploitation, and post‑exploitation on Unix‑like systems.

Common Commands

Navigation & File Management

Command	Description	Usage
pwd	Print working directory	pwd
cd	Change directory	cd [DIRECTORY]
ls	List directory contents	ls [OPTIONS] [FILE...]
tree	Recursively list directories as tree	tree [DIRECTORY]
mkdir	Create directory	mkdir [OPTIONS] DIRECTORY
rmdir	Remove empty directory	rmdir DIRECTORY
cp	Copy files or directories	cp SOURCE DEST
mv	Move or rename files/directories	mv SOURCE DEST
rm	Delete files or directories	rm [OPTIONS] FILE...
touch	Create empty file or update timestamp	touch FILENAME
ln	Create hard or symbolic links	ln [OPTIONS] TARGET LINK_NAME
stat	Display detailed file information	stat FILE
file	Detect file type	file FILE
basename	Strip directory and suffix from filename	basename PATH
dirname	Extract directory part of file path	dirname PATH
find	Search for files and directories	find [PATH] [OPTIONS] [EXPRESSION]
locate	Find files using database (faster than find)	locate FILENAME
chmod	Change file permissions	chmod [OPTIONS] MODE FILE
chown	Change file ownership (user)	chown [OPTIONS] USER FILE
chgrp	Change group ownership	chgrp [OPTIONS] GROUP FILE
umask	Set default file permission mask	umask [MASK]
tar	Archive files into tarball	tar -czf ARCHIVE.tar.gz FILES
gzip	Compress files using Gzip	gzip FILE
gunzip	Decompress Gzip files	gunzip FILE.gz
zip	Compress files into ZIP archive	zip ARCHIVE.zip FILES
unzip	Extract ZIP archive	unzip ARCHIVE.zip
dd	Copy and convert data (low-level)	dd if=SOURCE of=DEST bs=BLOCKSIZE
mount	Mount a filesystem	mount [DEVICE] [MOUNTPOINT]
umount	Unmount a filesystem	umount [MOUNTPOINT]

Viewing & Text Processing

Command	Description	Usage
cat	Concatenate & display files	cat [OPTIONS] FILE...
less	Paginate large files	less FILE
more	View file one page at a time	more FILE
head	Show first lines of a file	head [OPTIONS] FILE
tail	Show last lines / follow file	tail [OPTIONS] FILE
grep	Search for patterns	grep [OPTIONS] PATTERN FILE
awk	Pattern scanning & processing language	awk 'pattern { action }' FILE
sed	Stream editor for filtering & transforming text	sed [OPTIONS] 'SCRIPT' FILE
cut	Remove sections from each line	cut [OPTIONS] FILE
tr	Translate or delete characters	tr SET1 SET2
sort	Sort lines of text files	sort [OPTIONS] FILE
uniq	Filter out repeated lines	uniq [OPTIONS] FILE
wc	Count lines, words, bytes	wc [OPTIONS] FILE
nl	Number lines of a file	nl FILE
diff	Show differences between files	diff FILE1 FILE2
tee	Read from stdin and write to file and stdout	tee FILE

System & User Info

Command	Description	Usage
whoami	Show current user	whoami
id	Display user/group IDs	id [USERNAME]
df	Disk usage overview	df [OPTIONS]
du	Show disk usage for files/directories	du [OPTIONS] [PATH]
uptime	Show how long the system has been running	uptime
uname	System information (kernel, OS, architecture)	uname -a
hostname	Show or set system hostname	hostname
date	Display or set system date/time	date
cal	Display a calendar	cal
env	Show environment variables	env
set	Display shell variables and functions	set
history	List previously executed commands	history
ps	Display running processes	ps aux
top	Real-time system process monitor	top
kill	Terminate process by PID	kill [-9] PID
pkill	Kill processes by name	pkill PROCESS_NAME
pgrep	Search for processes by name	pgrep PROCESS_NAME
w	Show who is logged in and what they are doing	w
who	Show who is logged in	who
last	Show login history	last
free	Show memory usage	free -h

Networking

Command	Description	Usage
ping	Test network connectivity (ICMP)	ping [OPTIONS] DESTINATION
curl	Retrieve data from URLs / APIs	curl [OPTIONS] URL
ssh	Secure remote shell & tunnelling	ssh [OPTIONS] USER@HOST

Help & Documentation

Command	Description	Usage
man	Read manual pages	man COMMAND
echo	Display text / variables	echo [STRING]

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Examples

Print Working Directory

pwd

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Change Directory

cd /var/www

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List All Files (long + hidden)

ls -la

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Create Directory

mkdir backups

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Remove Empty Directory

rmdir backups

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Copy File

cp secrets.txt /tmp/secrets.bak

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Move & Rename

mv old.log archive/old.log

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Force‑Delete Directory

rm -rf /tmp/testdir

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Show File Contents

cat /etc/passwd | grep ":/bin/bash"

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View Large Log

less /var/log/auth.log

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First 10 Lines

head -n 10 notes.txt

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Follow File Growth

tail -f /var/log/nginx/access.log

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Search Pattern

grep -R \"passwd\" /etc

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Current User

whoami

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User & Group IDs

id

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Human‑Readable Disk Usage

df -h

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Show Last 20 Commands

history | tail -n 20

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Ping Host 4 Times

ping -c 4 example.com

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Download Web Page

curl -o index.html http://example.com

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SSH on Custom Port

ssh -p 2222 user@target

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Read Manual Page

man ssh

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Write to File

echo \"hacked\" > /tmp/proof.txt

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See Also

• Bash Scripting Basics
• Privilege Escalation
• Netcat