## 📝 Author

Birat Aryal — birataryal.github.io
Created Date: 2025-06-23
Updated Date: Monday 23rd June 2025 07:52:15
Website - birataryal.com.np
Repository - Birat Aryal
LinkedIn - Birat Aryal
DevSecOps Engineer | System Engineer | Cyber Security Analyst | Network Engineer

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🐧 Linux Cheat Sheet

📁 File & Directory Management

Command	Description
ls -l	List with long format
ls -a	Show hidden files
cd /path	Change directory
pwd	Show current directory
mkdir dir	Create directory
rmdir dir	Remove empty directory
rm -r dir	Remove directory and contents
cp file1 file2	Copy file
mv file1 file2	Move/rename file
touch file	Create empty file
find /path -name "*.txt"	Find files

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📝 File Viewing & Manipulation

Command	Description
cat file	View file
tac file	View file in reverse
more file / less file	Paginated view
head -n 10 file	First 10 lines
tail -n 10 file	Last 10 lines
tail -f file	Live log view
cut -d':' -f1 /etc/passwd	Column cut
awk '{print $1}' file	Print first field
sed 's/foo/bar/g' file	Replace in file

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🗃️ File Permissions

Command	Description
chmod 755 file	Set permission (u=rwx, g=rx, o=rx)
chown user file	Change owner
chown user:group file	Change owner and group
umask	Show default permission mask

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📦 Package Management

Debian/Ubuntu (apt)

Bash

apt update && apt upgrade
apt install <package>
apt remove <package>

Red Hat/CentOS/Alma (dnf/yum)

Bash

dnf install <package>
dnf remove <package>
dnf update

Arch (pacman)

Bash

pacman -Syu
pacman -S <package>
pacman -R <package>

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👤 User Management

Command	Description
adduser username	Add user
passwd username	Set user password
deluser username	Remove user
usermod -aG sudo user	Add to group
id user	Show user info
who / w / users	Logged-in users

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🧠 System Info & Resources

Command	Description
uname -a	Kernel and system info
uptime	System uptime
top / htop	Running processes
free -h	RAM usage
df -h	Disk usage
du -sh *	Folder sizes
lscpu / lsblk / lsusb / lspci	Hardware info
dmesg	Kernel logs
vmstat	Performance stats

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⚙️ Process Management

Command	Description
ps aux	All processes
kill PID	Kill process
killall process_name	Kill by name
nice -n 10 command	Set priority
renice -n 5 PID	Change priority

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🔐 Permissions & Security

Command	Description
chmod, chown, setfacl	File permissions
sudo	Run as root
visudo	Edit sudoers safely
firewall-cmd	Firewalld (RHEL)
ufw	Firewall (Ubuntu)
sshd, ss, iptables	SSH & networking

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🌐 Networking

Command	Description
ip a / ifconfig	Show IP address
ip r / route	Show routing
ping 8.8.8.8	Test connection
traceroute google.com	Trace route
netstat -tuln / ss -tuln	Open ports
dig domain.com / nslookup	DNS lookup
curl -I url	HTTP headers
wget url	Download file

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🔁 Archiving & Compression

Command	Description
tar -czvf archive.tar.gz folder/	Compress folder
tar -xzvf archive.tar.gz	Extract archive
zip -r file.zip folder/	Create ZIP
unzip file.zip	Extract ZIP
gzip file / gunzip file.gz	Compress/Extract GZ

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🛠️ Services & Startup

Command	Description
systemctl start service	Start service
systemctl stop service	Stop service
systemctl status service	Service status
systemctl enable service	Auto-start
systemctl disable service	Remove auto-start
journalctl -xeu servicename	Logs

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🐚 Bash & Scripting Basics

Syntax	Description
#!/bin/bash	Shebang line
var=value	Declare variable
echo $var	Print variable
read var	Get user input
if, elif, else, fi	Conditional
for, while, do, done	Loops
function fname {}	Define function
$(command)	Command substitution
"$@", $#, $?, $$	Script args, status, PID

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🧪 Useful Utilities

Command	Description
cron, crontab -e	Scheduled tasks
logrotate	Log file management
env, export	Environment variables
alias, unalias	Command shortcuts
xargs, tee, watch	Command chaining
ncdu, iotop, glances	Monitoring tools

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⏰ Cron Job Format

Text Only

* * * * * /path/to/script.sh
│ │ │ │ │
│ │ │ │ └─── Day of the week (0 - 7) (Sunday = 0 or 7)
│ │ │ └───── Month (1 - 12)
│ │ └─────── Day of month (1 - 31)
│ └───────── Hour (0 - 23)
└─────────── Minute (0 - 59)

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