Tech Study Guide

Debian and Ubuntu Operations

Ubuntu-first Linux operations: apt, dpkg, systemd, journald, netplan, ufw, CA certificates, logs, services, and package troubleshooting.

linux ubuntu debian operations

Debian and Ubuntu Operations

The study guide is Linux-first, but the default operational assumption is now Debian-family systems, especially Ubuntu Server. That matters because package tools, network configuration, service defaults, certificate stores, log locations, and firewall tooling differ by distribution. Canonical’s Ubuntu Server documentation tracks the latest LTS, so always check the target release notes or manpages before relying on release-specific behavior.

Command Examples

cat /etc/os-release
uname -a
apt-cache policy
systemctl --failed
journalctl -p warning..alert -b
ls -l /etc/netplan

Example output and meaning:

Command Example output What it does
cat /etc/os-release PRETTY_NAME="Ubuntu 24.04.2 LTS". Identifies the distro baseline before applying package or service commands.
uname -a Linux host 6.8.0-xx-generic x86_64. Shows kernel version and architecture for driver, eBPF, and tuning checks.
apt-cache policy Package versions, installed candidate, and repository priority. Shows what version apt can install or upgrade to.

Package Management

apt is the day-to-day package interface. dpkg is the lower-level package database and installer. Use apt-cache policy to see candidate versions and repositories before changing packages.

sudo apt update
apt-cache policy nginx
sudo apt install nginx
dpkg -l | grep nginx
dpkg -L nginx

Services and Logs

Ubuntu uses systemd by default. For most service incidents, start with:

systemctl status <service>
journalctl -u <service> -b
systemctl cat <service>
systemctl list-dependencies <service>

Package-owned unit files usually live under /usr/lib/systemd/system or /lib/systemd/system, with admin overrides under /etc/systemd/system.

Networking Defaults

Ubuntu Server commonly uses Netplan to describe network configuration, which then renders configuration for systemd-networkd or NetworkManager. Cloud images may also be influenced by cloud-init.

ip addr
ip route
resolvectl status
sudo netplan status
sudo netplan try

Firewall and Certificates

Ubuntu often uses ufw as a human-facing firewall tool over lower-level packet filtering.

sudo ufw status verbose
sudo nft list ruleset
sudo update-ca-certificates
ls -l /usr/local/share/ca-certificates /etc/ssl/certs

Troubleshooting Habits

  • Check /etc/os-release before assuming commands or paths.
  • Prefer journalctl for systemd services, but know app logs may still live in /var/log.
  • Use apt-cache policy before upgrades to understand repository sources.
  • Use sudo netplan try when changing remote network config.
  • Treat /usr/local/share/ca-certificates plus update-ca-certificates as the standard Ubuntu path for local root CAs.

Study Cards

Question

What is the default distro focus for this guide?

Answer

Debian-family Linux, especially Ubuntu Server, where distro-specific commands matter.

Question

What does apt-cache policy show?

Answer

Installed and candidate package versions plus the repositories that provide them.

Question

Why use netplan try remotely?

Answer

It applies network changes with rollback behavior if connectivity is lost or the change is not confirmed.

References