100 Linux Commands Every User Should Know

essential commands every system administrator, SAP HANA professional, and Linux user should know. Organized into clear categories like file management, networking, user control, and system monitoring, this guide serves as a daily reference for both beginners and experienced users. Whether you're troubleshooting servers, managing SAP HANA, or just exploring Linux, these commands will boost your productivity and command-line confidence.

📁 File and Directory Management

Command	Description	Example
ls	List files and directories	ls -l /home/user — Shows detailed list of files
cd	Change directory	cd /etc — Move to /etc directory
pwd	Show current directory path	pwd — Shows your current directory
mkdir	Create new directory	mkdir myfolder — Creates a folder named myfolder
rmdir	Remove empty directory	rmdir olddir — Deletes the directory if empty
rm	Remove files or directories	rm file.txt — Deletes file.txt
rm -r	Remove folders recursively	rm -r myfolder — Deletes folder and contents
cp	Copy files/directories	cp a.txt b.txt — Copies a.txt to b.txt
mv	Move or rename files/folders	mv old.txt new.txt — Renames file
touch	Create an empty file	touch notes.txt — Creates notes.txt
cat	View file contents	cat readme.txt — Prints file contents
more	View file contents page-wise	more bigfile.txt
less	Scrollable file viewer	less bigfile.txt
head	Show first lines of a file	head -n 10 file.txt
tail	Show last lines of a file	tail -n 10 file.txt
stat	Show file/directory details	stat file.txt
file	Show file type	file image.jpg
basename	Show filename from path	basename /path/to/file.txt
dirname	Show directory name from path	dirname /path/to/file.txt
find	Search files/directories	find /home -name '*.txt'

📦 File Permissions and Ownership

Command	Description	Example
chmod	Change file permissions	chmod 755 script.sh
chown	Change file owner	chown user:group file.txt
chgrp	Change group ownership	chgrp staff file.txt
umask	Default permission mask	umask 022
ls -l	View file permissions	ls -l file.txt

🔎 Search and Filter

Command	Description	Example
grep	Search in files	grep "error" logfile.log
egrep	Extended grep	`egrep "error
fgrep	Fixed-string grep	fgrep "error" logfile.log
locate	Find files by name (uses DB)	locate file.txt
which	Find location of command	which python
whereis	Locate binary/source/man	whereis ls
type	Display command type	type cd

💻 System Monitoring

Command	Description	Example
top	View real-time system processes	top
htop	Enhanced process viewer	htop
free -h	Show memory usage	free -h
df -h	Show disk space	df -h
du -sh	Folder size summary	du -sh *
vmstat	System performance	vmstat 1
iostat	CPU & disk I/O stats	iostat
uptime	Show uptime/load	uptime
who	Show logged-in users	who
w	Show who is logged in & what they are doing	w

🧩 User and Group Management

Command	Description	Example
adduser	Add new user	adduser sanjay
useradd	Add user (low-level)	useradd -m raj
passwd	Change password	passwd sanjay
deluser	Remove a user	deluser sanjay
usermod	Modify user	usermod -aG sudo sanjay
groupadd	Create group	groupadd admin
groupdel	Delete group	groupdel admin
groups	Show user's groups	groups sanjay
id	Show UID/GID of user	id sanjay

🔐 Network Commands

Command	Description	Example
ping	Test connectivity	ping google.com
netstat	Network statistics	netstat -tulpn
ss	Socket statistics	ss -tuln
ifconfig	Show IP info (older)	ifconfig
ip addr	Show IP info (modern)	ip addr show
hostname	Show system name	hostname
traceroute	Trace route to host	traceroute google.com
nslookup	DNS lookup	nslookup openai.com
curl	Fetch URL data	curl http://example.com
wget	Download file	wget http://example.com/file.txt

⚙️ Process Management

Command	Description	Example
ps	Show processes	`ps aux
kill	Kill a process	kill 1234
killall	Kill by name	killall firefox
nice	Start process with priority	nice -n 10 command
renice	Change process priority	renice -n 5 -p 1234

🗃️ Archives and Compression

Command	Description	Example
tar	Create/extract archive	tar -czf archive.tar.gz folder/
gzip	Compress file	gzip file.txt
gunzip	Decompress .gz file	gunzip file.txt.gz
zip	Create zip archive	zip file.zip file1 file2
unzip	Extract zip file	unzip file.zip

⌛ Scheduling and Background Tasks

Command	Description	Example
cron	Schedule jobs	Edit with crontab -e
at	Run command at a certain time	at 14:00
bg	Resume job in background	bg %1
fg	Bring job to foreground	fg %1
jobs	List background jobs	jobs

🧹 System Utilities

Command	Description	Example
clear	Clear terminal screen	clear
history	Show command history	history
alias	Create shortcut	alias ll='ls -l'
uname -a	Show system info	uname -a
date	Show current date/time	date
cal	Show calendar	cal
echo	Display message	echo Hello World
whoami	Show current user	whoami