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

ln || Create hard or symbolic links || ln [OPTIONS] TARGET LINK_NAMEfind || Search for files and directories || find [PATH] [OPTIONS] [EXPRESSION]chmod || Change file permissions || chmod [OPTIONS] MODE FILEchown || Change file ownership (user) || chown [OPTIONS] USER FILEchgrp || Change group ownership || chgrp [OPTIONS] GROUP FILEumask || Set default file permission mask || umask [MASK]tar || Archive files into tarball || tar -czf ARCHIVE.tar.gz FILESgzip || Compress files using Gzip || gzip FILEzip || Compress files into ZIP archive || zip ARCHIVE.zip FILES

Command	Description	Usage
pwd	Print working directory	pwd [OPTIONS]
cd	Change directory	cd [DIRECTORY]
ls	List directory contents	ls [OPTIONS] [FILE...]
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

Viewing & Text Processing

Command	Description	Usage
cat	Concatenate & display files	cat [OPTIONS] FILE...
less	Paginate large files	less 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

System & User Info

Command	Description	Usage
whoami	Show current user	whoami
id	Display user/group IDs	id [USERNAME]
df	Disk usage overview	df [OPTIONS]
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

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