Linux Terminal: Vital Commands

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

ls -lah

When to use: When 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 use: For 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 use: To 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 use: When 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 use: To 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.shchmod 644 arquivo.txt

When to use: 755 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.shchmod go-w arquivo.txt

When to use: When 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 use: To correct permissions after deployment or web server configuration

Displays file permissions in numeric format

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

When to use: To quickly check the numeric value of current permissions

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

ps aux | grep usuariops -ef | grep nginx

When to use: To identify PIDs of specific processes or diagnose resource usage

Interactive interface with real-time process updates

tophtop

When to use: For continuous monitoring of CPU, memory, and identifying problematic processes

Terminates process using different signal levels

kill 1234kill -9 1234kill -SIGTERM 1234

When to use: kill for graceful termination, kill -9 to force immediate termination

Terminates all processes matching the name

pkill nginxkillall node

When to use: When 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 use: To 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.comping 192.168.1.1

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

Downloads files from the web via HTTP/HTTPS

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

When to use: wget for simple downloads, curl for APIs and more complex requests

Lists all open TCP/UDP ports and associated processes

netstat -tulpnss -tulpn

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

Discovers the machine's public IP address

curl ifconfig.mewget -qO- ifconfig.me

When to use: To know your public IP when working remotely or configuring firewalls

Synchronizes the list of available packages with repositories

sudo apt update

When to use: Always before installing new packages to ensure updated versions

Downloads and installs package with all dependencies

sudo apt install nginx -y

When to use: To install software via official repositories (-y automatically confirms)

Updates all installed packages to newer versions

sudo apt update && sudo apt upgrade -y

When to use: Regular system maintenance for security patches and improvements

Uninstalls package, keeping configuration files

sudo apt remove pacotesudo apt purge pacote

When to use: remove keeps configs, purge removes everything (useful for clean reinstallation)

Searches for available packages in repositories

apt search python3apt-cache search nodejs

When to use: To find the exact package name before installing

Displays used and available space on all mounted partitions

df -h

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

Calculates total size of directories and files

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

When to use: To identify which directories are consuming the most space

Shows RAM and swap usage in human-readable format

free -h

When to use: To diagnose memory issues or check if swap is being used

Displays processor details (model, cores, frequency)

lscpucat /proc/cpuinfo

When to use: To check hardware specifications before optimizations

Shows how long the system has been running and average load

uptime

When to use: To check server stability and load average

Identifies Linux distribution and kernel version

uname -acat /etc/os-release

When to use: To document environment or check software compatibility