Linux Terminal: Vital Commands

Lists all files including hidden ones with permission, size, and date details

ls -lah

When to useWhen you need to view all files with detailed information, including hidden files (starting with .)

Copies directories and their content recursively, preserving attributes

cp -r /origem /destino

When to useFor backing up entire directories or duplicating folder structures

Moves files/directories or renames if destination is in the same directory

mv arquivo.txt /novo/caminho/
mv arquivo_antigo.txt arquivo_novo.txt

When to useTo organize files or rename them directly via the terminal

Locates files in the system recursively using glob patterns

find /caminho -name "*.log"
find . -type f -name "config*"

When to useWhen you need to locate specific files in large directory structures

Creates multiple levels of directories at once

mkdir -p /projeto/src/components/ui

When to useTo quickly create complex folder structures without needing to create each level manually

Sets permissions using octal notation (rwx = 7, rw- = 6, r-x = 5)

chmod 755 script.sh
chmod 644 arquivo.txt

When to use755 for executables (rwxr-xr-x), 644 for data files (rw-r--r--)

Modifies permissions using symbolic notation (u=user, g=group, o=others)

chmod u+x script.sh
chmod go-w arquivo.txt

When to useWhen you want to modify specific permissions without changing others

Changes the owner and group of files/directories recursively

chown -R usuario:grupo /var/www/html

When to useTo correct permissions after deployment or web server configuration

Displays file permissions in numeric format

stat -c '%a %n' arquivo.txt

When to useTo quickly check the numeric value of current permissions

Displays all processes of the current user with CPU and memory details

ps aux | grep usuario
ps -ef | grep nginx

When to useTo identify PIDs of specific processes or diagnose resource usage

Interactive interface with real-time process updates

top
htop

When to useFor continuous monitoring of CPU, memory, and identifying problematic processes

Terminates process using different signal levels

kill 1234
kill -9 1234
kill -SIGTERM 1234

When to usekill for graceful termination, kill -9 to force immediate termination

Terminates all processes matching the name

pkill nginx
killall node

When to useWhen you know the process name but not the PID

Starts process in the background, freeing up the terminal

npm run dev &
nohup python3 script.py &

When to useTo run long scripts without blocking the terminal (nohup keeps it running after logout)

Sends ICMP packets to check if the host is reachable

ping -c 4 google.com
ping 192.168.1.1

When to useTo check network connectivity and latency (-c limits the number of packets)

Downloads files from the web via HTTP/HTTPS

wget https://example.com/file.zip
curl -O https://example.com/file.tar.gz

When to usewget for simple downloads, curl for APIs and more complex requests

Lists all open TCP/UDP ports and associated processes

netstat -tulpn
ss -tulpn

When to useTo identify port conflicts or check if a service is listening

Copies files between machines via SSH

scp arquivo.txt user@servidor:/path/
scp -r /pasta user@servidor:/destino

When to useTo securely transfer files between servers (use -r for directories)

Discovers the machine's public IP address

curl ifconfig.me
wget -qO- ifconfig.me

When to useTo know your public IP when working remotely or configuring firewalls

Synchronizes the list of available packages with repositories

sudo apt update

When to useAlways before installing new packages to ensure updated versions

Downloads and installs package with all dependencies

sudo apt install nginx -y

When to useTo install software via official repositories (-y automatically confirms)

Updates all installed packages to newer versions

sudo apt update && sudo apt upgrade -y

When to useRegular system maintenance for security patches and improvements

Uninstalls package, keeping configuration files

sudo apt remove pacote
sudo apt purge pacote

When to useremove keeps configs, purge removes everything (useful for clean reinstallation)

Searches for available packages in repositories

apt search python3
apt-cache search nodejs

When to useTo find the exact package name before installing

Displays used and available space on all mounted partitions

df -h

When to useTo check for sufficient disk space (-h displays in human-readable format)

Calculates total size of directories and files

du -sh /var/log
du -h --max-depth=1 /home

When to useTo identify which directories are consuming the most space

Shows RAM and swap usage in human-readable format

free -h

When to useTo diagnose memory issues or check if swap is being used

Displays processor details (model, cores, frequency)

lscpu
cat /proc/cpuinfo

When to useTo check hardware specifications before optimizations

Shows how long the system has been running and average load

uptime

When to useTo check server stability and load average

Identifies Linux distribution and kernel version

uname -a
cat /etc/os-release

When to useTo document environment or check software compatibility