20 Essential Linux Commands for the Beginner VPS Sysadmin

Find the current directory and list its contents:

pwd
ls -lah

pwd (print working directory) shows the absolute path where you are — useful when you get lost after several cd calls. ls -lah lists files with permissions (l), human-readable sizes (h), and includes hidden files (a). It’s the canonical way to inspect a directory.

Change directories and jump back quickly:

cd /var/log
cd -
cd ~

cd /var/log enters an absolute path. cd - returns to the previous directory — a shortcut that saves a lot of time. cd ~ (or just cd) goes to your home (/home/your-user).

Create and remove directories and files:

mkdir -p projects/site/logs
touch projects/site/index.html
rm -ri projects/test

mkdir -p creates the entire tree at once (doesn’t fail if intermediates already exist). touch creates an empty file or updates its timestamp. rm -ri removes with interactive confirmation — recommended while you don’t yet trust your paths 100%.

View small and large files:

cat /etc/hostname
less /var/log/syslog
tail -f /var/log/auth.log
head -n 50 /etc/ssh/sshd_config

cat dumps the entire file — good for short files. less opens navigable pagination (arrows, / to search, q to quit) — use it whenever the file exceeds one screen. tail -f follows files being written in real time, like logs. head -n 50 shows only the first 50 lines.

Edit files directly in the terminal:

sudo nano /etc/ssh/sshd_config

nano is the friendliest editor for people coming from a GUI — shortcuts are shown on the bottom bar (Ctrl+O saves, Ctrl+X exits). When you gain more experience, the professional standard is vim or vi, present on any server even the most minimal.

Adjust permissions on files and directories:

chmod 644 index.html
chmod 755 /var/www/site
chmod +x script.sh

The numbers are octal: 644 = owner reads/writes, others only read. 755 = owner can do everything, others read and execute (required for directories). +x adds execute permission for everyone without touching the rest — a handy shortcut for scripts.

Change file owner and group:

sudo chown www-data:www-data /var/www/site -R

chown user:group file changes owner and group. The -R flag applies recursively across the whole tree. Classic case: after running git clone as your user, adjust ownership to the web server user so it can serve the files.

Monitor processes in real time:

top
htop

top ships with any Linux — q quits, M sorts by memory, P by CPU. htop (install with sudo apt install htop) is the modern version: colors, arrow navigation, F9 to kill a process. For production VPS, keep htop installed by default.

List and kill specific processes:

ps aux | grep nginx
sudo kill 1234
sudo kill -9 1234

ps aux lists all system processes; combined with grep, it filters by name. kill PID sends SIGTERM (polite termination). kill -9 PID sends SIGKILL (brute force) — use only when SIGTERM doesn’t resolve it, because it gives the process no chance to clean up state.

Check disk and memory usage:

df -h
du -sh /var/log/*
free -h

df -h shows free space per partition in human-readable format. du -sh /path/* shows the size of each item inside the path — invaluable for finding out who’s filling the disk. free -h shows total, used, and available RAM.

View interfaces, IPs, and listening ports:

ip addr
ss -tulpn

ip addr (or ip a) shows IPs configured on each interface — replaces the old ifconfig. ss -tulpn lists all open TCP/UDP ports and which process is listening — replaces the old netstat. Memorize this command: tcp, udp, listen, process, numeric.

Test connectivity and DNS:

ping -c 4 hostini.com.br
curl -I https://hostini.com.br
dig hostini.com.br

ping -c 4 sends 4 ICMP packets — confirms the machine reaches the destination. curl -I issues an HTTP HEAD request — confirms the web application responds, showing headers. dig resolves DNS in detail — useful when ping works by IP but fails by name.

Update the index and install packages:

sudo apt update
sudo apt upgrade -y
sudo apt install -y nginx git curl
sudo apt remove --purge old-package

apt update downloads the up-to-date package list — doesn’t install anything yet. apt upgrade applies available updates. apt install downloads and installs; -y confirms automatically. remove --purge uninstalls including configuration files.

Query system logs with journalctl:

journalctl -p err -n 50
journalctl -u nginx -f
journalctl --since "1 hour ago"

journalctl is the unified log interface on systemd distros. -p err filters only errors, -n 50 shows the last 50 lines. -u nginx -f follows the nginx service in real time. --since accepts natural expressions (“yesterday”, “2 hours ago”).

Manage system services:

sudo systemctl status nginx
sudo systemctl restart nginx
sudo systemctl enable nginx

status shows whether the service is running plus the latest log lines. restart restarts it (use after changing config). enable makes the service start automatically on boot — forgetting this is a common cause of “the site didn’t come back after the reboot”.