essential-commands.md

Essential Linux Commands Cheatsheet

Navigation

Command	Description
pwd	Print working directory
cd /path	Change directory
cd ~ or cd	Go to home
cd -	Go to previous directory
ls -la	List all files with details
tree -L 2	Show directory tree

File Operations

Command	Description
cp src dst	Copy file
cp -r src dst	Copy directory
mv src dst	Move/rename
rm file	Delete file
rm -rf dir	Delete directory
mkdir -p a/b/c	Create nested dirs
touch file	Create empty file
ln -s target link	Symbolic link

Viewing Files

Command	Description
cat file	Print entire file
less file	Paginated viewing
head -20 file	First 20 lines
tail -20 file	Last 20 lines
tail -f file	Follow file (live)
wc -l file	Count lines

Searching

Command	Description
find / -name "*.log"	Find by name
find / -size +100M	Find by size
find / -mtime -7	Modified last 7 days
grep "text" file	Search in file
grep -r "text" /dir	Recursive search
grep -i "text" file	Case-insensitive
which command	Find command path
locate filename	Fast file search

Permissions

Command	Description
chmod 755 file	rwxr-xr-x
chmod 644 file	rw-r--r--
chmod +x file	Add execute
chown user:group file	Change owner
chown -R user dir	Recursive owner

Disk & Storage

Command	Description
df -h	Disk usage (filesystems)
du -sh /dir	Directory size
du -sh * | sort -rh	Sorted sizes
lsblk	Block devices
mount | column -t	Mounted filesystems
free -h	Memory usage

Process Management

Command	Description
ps aux	All processes
top / htop	Interactive monitor
kill PID	Graceful kill
kill -9 PID	Force kill
killall name	Kill by name
bg / fg	Background / foreground
jobs	List background jobs
nohup cmd &	Run after logout

Networking

Command	Description
ip addr show	Show IP addresses
ip route show	Show routes
ping host	Test connectivity
ss -tuln	Listening ports
curl -I url	HTTP headers
dig domain	DNS lookup
traceroute host	Trace route
wget url	Download file

Archives

Command	Description
tar -czf a.tar.gz dir/	Create .tar.gz
tar -xzf a.tar.gz	Extract .tar.gz
tar -xjf a.tar.bz2	Extract .tar.bz2
zip -r a.zip dir/	Create zip
unzip a.zip	Extract zip

System Info

Command	Description
uname -a	System info
hostnamectl	Hostname & OS
uptime	Uptime & load
whoami	Current user
id	User ID & groups
date	Current date/time
last	Recent logins

Package Management

Distro	Install	Update	Remove	Search
Debian/Ubuntu	apt install pkg	apt update && apt upgrade	apt remove pkg	apt search pkg
Fedora/RHEL	dnf install pkg	dnf upgrade	dnf remove pkg	dnf search pkg
Arch	pacman -S pkg	pacman -Syu	pacman -R pkg	pacman -Ss pkg

Pipes & Redirection

Syntax	Description
cmd > file	Stdout to file (overwrite)
cmd >> file	Stdout to file (append)
cmd 2> file	Stderr to file
cmd &> file	Both stdout+stderr
cmd1 | cmd2	Pipe output to next
cmd < file	File as stdin
cmd1 && cmd2	Run cmd2 only if cmd1 succeeds
cmd1 || cmd2	Run cmd2 only if cmd1 fails