System Level Commands Guide

If I had to relearn Linux for observability…

I would master basic system-level commands —

because observability is not just about metrics —

it’s about knowing the system you are observing.

🛠️ System-Level Commands Explained

1️⃣ uname

uname -a        

• Shows system information: kernel name, version, architecture.

✅ Check if the server is Linux, what version, what hardware.

2️⃣ uptime

uptime        

• Shows how long the system has been running + load average.

✅ Great to know if the server recently rebooted or is under load.

3️⃣ date

date        

• Displays current system date and time.

✅ Critical for log correlation and time-sensitive debugging.

4️⃣ who and whoami

who        

• Shows who is logged in to the system.

whoami        

• Shows your own username.

✅ Good for checking active sessions and permissions.

5️⃣ which

which nginx        

• Shows the path of a binary (program) that will run when you type the command.

✅ Useful for verifying which version or path of a tool is being used.

6️⃣ id

id        

• Displays UID, GID, and groups of the current user.

✅ Important for permission and security audits.

7️⃣ sudo

sudo command        

• Runs a command as another user (usually root) temporarily.

✅ Essential for privileged operations — but needs careful monitoring.

8️⃣ shutdown

sudo shutdown now        

• Safely powers off the system.

✅ Always prefer controlled shutdowns over power cuts.

9️⃣ reboot

sudo reboot        

• Restarts the server cleanly.

✅ Useful for applying kernel updates or recovering after major config changes.

10️⃣ apt

sudo apt update
sudo apt install nginx        

• Package manager for Debian/Ubuntu systems.

✅ Used to install, update, upgrade, or remove software.

11️⃣ yum

sudo yum install nginx        

• Older package manager for Red Hat/CentOS systems.

✅ Used similarly for installing/removing software.

12️⃣ dnf

sudo dnf install nginx        

• Modernized yum, used by newer Red Hat-based systems (Fedora, RHEL8+).

✅ Faster and smarter dependency handling.

13️⃣ pacman

sudo pacman -S nginx        

• Package manager for Arch Linux.

✅ Very lightweight and efficient for bleeding-edge setups.

14️⃣ portage

emerge nginx        

• Advanced source-based package manager for Gentoo Linux.

✅ Powerful but complex — compiles packages from source.

🧠 Simple Analogy

Think of your Linux server like a restaurant kitchen:

• uname = What kind of kitchen is it?
• uptime = How long has it been open today?
• date = What's the time now?
• who / whoami = Who's currently working?
• which = Where is the knife (binary) stored?
• id = What's the chef's ID badge (UID/GID)?
• sudo = Asking the head chef for permission to use restricted tools.
• shutdown = Closing the kitchen.
• reboot = Restarting the kitchen after cleaning.
• apt/yum/dnf/pacman/portage = Ordering new ingredients (software) from different suppliers (package managers).

🗺️ Where Are We in the Linux Journey?

System Basics → User Sessions → Package Management → Admin Privileges → Full Observability        

✅ Understanding these commands gives you confidence when investigating or fixing a server.