Linux Essentials Guide: Master the Essential Commands

If you're starting your Linux journey or already manage servers and want to review the basics, this guide is for you. Mastering basic commands not only speeds up your routine, it also gives you more confidence to solve problems, automate tasks and better understand what happens under the hood.

In this article we'll explore the essential Linux commands in a practical, hands-on way, without dumping a pile of loose instructions. Each command comes with context, real examples, use cases and practical mini tutorials for you to try right in the terminal.

📂 Exploring Files and Folders with ls

ls is the most commonly used command to list files and directories. It looks simple, but with a few parameters it becomes powerful.

# Listar arquivos e pastas
ls


# Listar em formato detalhado (permissões, dono, tamanho, data)
ls -l


# Incluir arquivos ocultos (aqueles que começam com .)
ls -la


# Ordenar por data de modificação (mais recentes no fim)
ls -lt

💡 Extra tip: combine ls -lh to see human-readable sizes (KB, MB, GB).

Mini tutorial:

cd ~ # Vá para sua pasta pessoal
mkdir teste # Crie uma pasta chamada teste
cd teste # Acesse a pasta criada
ls -la # Liste os arquivos e confirme que está vazia

Linux • Command

Quick comparison: ls with different parameters

Open the items to see the description and typical output.

$ ls
arquivo1.txt  notas.md  pasta1/  script.sh

$ ls -l
-rw-r--r-- 1 user user  1240 Jan 21 10:15 script.sh
drwxr-xr-x 3 user user  4096 Jan 20 09:02 pasta1
-rw-r--r-- 1 user user  2789 Jan 18 18:40 notas.md

$ ls -a
.  ..  .gitignore  .env  arquivo1.txt  pasta1  script.sh

$ ls -lh
-rw-r--r-- 1 user user 12K Jan 21 10:15 script.sh
-rw-r--r-- 1 user user 2.7K Jan 18 18:40 notas.md

$ ls -R
.:
arquivo1.txt  pasta1

./pasta1:
subpasta  dados.csv

./pasta1/subpasta:
notas.md

$ ls -lt
-rw-r--r-- 1 user user 2.7K Jan 22 09:10 changelog.md
-rw-r--r-- 1 user user  12K Jan 21 10:15 script.sh

$ ls -lah
drwxr-xr-x  6 user user 4.0K Jan 22 09:10 .
drwxr-xr-x 18 user user 4.0K Jan 20 08:00 ..
-rw-r--r--  1 user user 2.7K Jan 18 18:40 .env
-rw-r--r--  1 user user  12K Jan 21 10:15 script.sh

🔒 Permissions with chmod

On Linux, every file and directory has read, write and execute permissions for the user, group and others.

# Dar permissão de execução a um script
chmod +x script.sh


# Definir permissões numéricas (r=4, w=2, x=1)
chmod 755 script.sh

• 755 → the owner can do everything; group and others can only read and execute.
• 644 → the owner can read and write; group and others can only read.

Mini tutorial:

touch meu_script.sh # Crie um arquivo vazio
ls -l meu_script.sh # Veja as permissões atuais
chmod +x meu_script.sh # Adicione permissão de execução
ls -l meu_script.sh # Confira a mudança

Linux • Permissions and Metadata

Understanding Every Number and Permission in ls -l

Open the items to see descriptions, examples and tips.

$ ls -l
-rw-r--r-- 1 alice dev 2789 Jan 18 18:40 notas.md
^ ^^^^^^^^^ ^ ^^^^^ ^^^^ ^^^ ^^ ^^ ^^^^^^^
| |         | |     |    |   |  |  └─── Nome (+ "→ alvo" se link)
| |         | |     |    |   └────── Data/Hora
| |         | |     |    └────────── Tamanho (bytes; use -h p/ KB/MB)
| |         | |     └─────────────── Grupo
| |         | └────────────────────── Dono (usuário)
| |         └──────────────────────── Nº de links (hard links / dirs)
| └────────────────────────────────── Permissões (rwx para U/G/O)
└──────────────────────────────────── Tipo de arquivo (-, d, l, c, b, p, s)

-rw-r--r--  → dono: rw-, grupo: r--, outros: r--

chmod u+s arquivo   # setuid
chmod g+s pasta     # setgid
chmod +t  pasta     # sticky

$ ln arquivo a2 && ls -l arquivo a2
-rw-r--r-- 2 alice dev 0 Jan 21 10:00 a2
-rw-r--r-- 2 alice dev 0 Jan 21 10:00 arquivo  # “2” = dois nomes p/ o mesmo inode

$ chown alice:dev arquivo   # muda dono e grupo
$ chgrp dev arquivo         # muda só o grupo

$ ls -lh /dev/null
crw-rw-rw- 1 root root 1, 3 Jan  1 12:00 /dev/null   # major,minor

$ ln -s /etc/hosts hosts-link && ls -l hosts-link
lrwxrwxrwx 1 alice dev 10 Jan 21 10:20 hosts-link → /etc/hosts

7 = rwx (4+2+1)
6 = rw- (4+2)
5 = r-x (4+1)
4 = r-- (4)
0 = ---

# Exemplos
chmod 644 arquivo   # -rw-r--r--
chmod 755 script.sh # -rwxr-xr-x
chmod 770 pasta     # rwx para dono e grupo; outros sem acesso

⚙️ Managing Processes with ps and kill

Every running process on Linux has a PID (Process ID). To find and terminate processes, we use ps and kill.

# Listar processos do usuário atual
ps


# Listar todos os processos
ps aux


# Procurar por um processo específico (exemplo: nginx)
ps aux | grep nginx


# Encerrar processo pelo PID
kill 1234


# Encerrar processo à força
kill -9 1234

💡 Best practice: before using kill -9, try to terminate the process normally. The -9 signal forces termination and can cause problems if the process is handling files.

Mini tutorial:

sleep 1000 & # Crie um processo de teste em background
ps aux | grep sleep # Encontre o PID
kill <PID> # Encerre o processo

Linux • Processes

Steps: Finding and Terminating Processes

Use with care ⚠️ terminating critical processes can freeze the system.

1. 1

   List running processes

   $ ps aux        # visão geral
   $ top           # monitor interativo
   $ htop          # versão avançada (se instalado)

2. 2

   Find by name

   $ pidof firefox        # retorna PID
   $ pgrep -l nginx       # lista PIDs + nomes
   $ ps aux | grep python # filtra manualmente

3. 3

   Terminate by PID

   $ kill 1234       # encerra com SIGTERM (educado)
   $ kill -9 1234    # encerra forçado (SIGKILL)

4. 4

   Terminate by name

   $ killall firefox   # encerra todos os processos firefox
   $ pkill -f script.py # encerra por padrão ou comando

5. 5

   Confirm the process stopped

   $ pgrep firefox  # nada retornado → sucesso
   $ ps aux | grep nome

🔄 Controlling Services with systemctl

systemctl is used to manage services on modern Linux distributions that use systemd as their init system (such as Ubuntu, Debian and CentOS). It is the standard tool for controlling and monitoring system services.

# Iniciar um serviço
sudo systemctl start nginx


# Parar um serviço
sudo systemctl stop nginx


# Reiniciar um serviço
sudo systemctl restart nginx


# Verificar status
sudo systemctl status nginx


# Habilitar para iniciar automaticamente no boot
sudo systemctl enable nginx

Mini tutorial:

sudo systemctl status ssh # Veja se o SSH está rodando
sudo systemctl stop ssh # Pare o serviço
sudo systemctl start ssh # Inicie novamente

Click here to read more about How to Manage an Ubuntu Server with systemctl and Other Essential Commands.

🌐 Network Configuration with ifconfig and ip

Historically, we used ifconfig. Today the recommended command is ip.

# Ver interfaces de rede
ifconfig


# Alternativa moderna
ip addr show


# Exibir rotas
ip route


# Subir ou derrubar interface de rede
sudo ip link set eth0 up
sudo ip link set eth0 down

Mini tutorial:

ip addr show # Veja suas interfaces
ping 8.8.8.8 # Teste conectividade com Google DNS

💡 Extra tip: ip is more complete and supported on modern systems. Use it whenever possible.

🌐 ifconfig × ip

The ifconfig command is obsolete on most distros. ip is the modern, more powerful alternative.

🕹️ ifconfig (old)

• ifconfig → list interfaces
• ifconfig eth0 up → enable the interface
• ifconfig eth0 192.168.1.10 → assign an IP

⚡ ip (modern)

• ip addr → list interfaces
• ip link set eth0 up → enable the interface
• ip addr add 192.168.1.10/24 dev eth0 → assign an IP

💡 Tip: always use ip for better compatibility and extra features (ip route, ip neigh, etc.).

📡 Monitoring Connections with netstat and ss

netstat is a classic, but just like ifconfig, it is being replaced by ss.

# Mostrar conexões ativas
netstat -tulnp


# Usando ss (mais rápido e moderno)
ss -tulnp


# Ver portas abertas
ss -ltn

• -t → TCP connections
• -u → UDP connections
• -l → listening services
• -n → show numeric IPs/ports
• -p → show the associated process

Mini tutorial:

ss -ltn # Veja portas abertas
ss -tulnp # Veja processos associados

🔗 netstat × ss

netstat is obsolete on several distributions. Use ss as a faster, more modern alternative.

💡 ss is more efficient on modern systems and can replace practically every use of netstat.

✍️ Creating and Editing Files

Besides managing processes and networks, you'll need to handle files every day. Here are some fundamental commands:

# Criar um arquivo vazio
touch exemplo.txt


# Adicionar conteúdo com echo
echo "Olá Linux!" > exemplo.txt


# Visualizar conteúdo com cat
cat exemplo.txt


# Editar com nano
nano exemplo.txt


# Editar com vim
vim exemplo.txt


# Renomear arquivo
mv exemplo.txt novo_nome.txt


# Apagar arquivo
rm novo_nome.txt

Mini tutorial:

cd ~
mkdir projeto
cd projeto
touch notas.txt
nano notas.txt # Escreva algo e salve (CTRL+O, ENTER, CTRL+X)
cat notas.txt # Veja o conteúdo
mv notas.txt ideia.txt
rm ideia.txt

🎯 Extra Tips for Everyday Use

Ready-to-Copy Shortcuts

Use man <comando> for help • combine pipes | for powerful filters • create aliases to speed things up.

# Listagem detalhada + ocultos + tamanhos legíveis
alias ll='ls -lah'
# Listagem leve com colunas
alias l='ls -CF'
# Apenas ocultos inclusos (sem . e ..)
alias la='ls -A'
# Ordenar por tempo (mais recentes no fim) e tamanhos legíveis
alias lt='ls -lht'

# Subir diretórios rápido
alias ..='cd ..'
alias ...='cd ../..'
alias ....='cd ../../..'
# Voltar ao diretório anterior
alias -- -='cd -'
# Criar pasta e entrar
mkcd(){ mkdir -p "$1" && cd "$1"; }

# Status curto + branch/graph
alias gs='git status -sb'
# Add tudo e commit rápido
alias ga='git add -A'
alias gc='git commit -m'
# Push/pull diretos
alias gp='git push'
alias gpl='git pull --rebase'
# Log compacto
alias gl='git log --oneline --graph --decorate --all'

# Meu IP público
alias myip='curl -s https://ifconfig.me'
# Interfaces e endereços
alias ipa='ip -brief addr'
# Portas em escuta (TCP)
alias listen='ss -lnt'
# Rotas rápidas
alias routes='ip route show'

# Buscar processo por nome (case-insensitive)
psg(){ ps aux | grep -i --color=auto "$1"; }
# Encerrar com SIGKILL rapidamente
alias k9='kill -9'
# Top simplificado (se instalado)
alias htop5='htop -d 10'

# Uso de disco por FS (legível + tipo)
alias dfh='df -hT'
# Espaço por pasta (ordem crescente)
alias duh='du -sh -- * | sort -h'
# Repetir último comando com sudo
please(){ sudo $(fc -ln -1); }

echo "alias ll='ls -la'" >> ~/.bashrc
# Dica: cole também outros aliases acima no mesmo arquivo
source ~/.bashrc
ll  # Agora você pode usar ll no lugar de ls -la

🔗 External References

• Arch Linux Coreutils documentation
• systemd documentation
• Official guide to the ip command
• ss command manual

🚀 Conclusion

Mastering essential Linux commands is like learning to drive: at first it seems like a lot, but soon it becomes second nature. Every command presented here, from the simple ls to the powerful systemctl, is a tool that will make you more productive and safer when using the system.

👉 Now it's your turn: open a terminal and follow this article's mini tutorials. Try creating files, editing with nano, killing processes and checking open ports. The more you practice, the more natural your command of Linux will be.

And if you want to deepen your knowledge of Linux, automation and DevOps, keep following the Forcoder blog. 😉