How to Update Ubuntu/Debian with apt update & apt upgrade

What this is

This guide explains how to update an Ubuntu or Debian server using apt (the package manager).

What it is for

• Install security patches and bug fixes
• Keep your VPS stable and supported
• Reduce risk of vulnerabilities

Prerequisites

• SSH access to your VPS
• A user with sudo privileges (or root)
• Recommended: a backup/snapshot before updating

Step-by-step (extremely detailed)

Step 1) Confirm the OS is Ubuntu/Debian

cat /etc/os-release

What it does: Shows your distribution and version.

Why it is needed: These commands are specifically for APT-based systems.

Expected output: Lines like NAME="Ubuntu" or NAME="Debian".

Step 2) Update the package list

sudo apt update

What it does: Downloads the latest package index from your repositories.

Why it is needed: Without this, your server may not “see” the newest updates.

Expected output: You will see repository lines and a final message like Reading package lists... Done.

Warning: If you see repository errors, stop and fix them before upgrading.

Step 3) See what would be upgraded (optional but recommended)

apt list --upgradable

What it does: Lists packages with available upgrades.

Expected output: A list of packages (or nothing if up to date).

Step 4) Install upgrades

sudo apt upgrade -y

What it does: Upgrades installed packages to newer versions.

Why it is needed: This is the main step that applies security patches.

Expected output: Downloads and installs packages; may restart some services.

Important note: If it says packages are “kept back”, run the next step.

Step 5) If packages were kept back: full upgrade

sudo apt full-upgrade -y

What it does: Upgrades packages even when dependencies change.

Why it is needed: Kernel and some system updates require dependency changes.

Expected output: Similar to apt upgrade, but may install/remove packages as needed.

Warning: Read the summary; it may remove packages (rare, but possible).

Step 6) Clean up unused packages

sudo apt autoremove -y

What it does: Removes packages no longer required.

Why it is needed: Saves disk space and reduces clutter.

Expected output: A list of packages removed (or nothing to remove).

Step 7) Check if a reboot is required

if [ -f /var/run/reboot-required ]; then echo "Reboot required"; else echo "No reboot required"; fi

What it does: Checks if Ubuntu/Debian marked the system for reboot.

Expected output: Reboot required or No reboot required.

Step 8) Reboot (only if needed)

sudo reboot

What it does: Restarts the server.

Expected result: SSH disconnects. Wait 30–120 seconds, then reconnect.

Final verification

Verify the server is up

uptime

Expected output: Shows load and uptime (after reboot it should be low).

Verify no failed services

systemctl --failed

Expected output: Ideally 0 loaded units listed.

Conclusion

You updated your Ubuntu/Debian server safely. Repeat this regularly (weekly/monthly) to keep your VPS secure.