Tecmint: Linux Inside

When a Linux service stops working as expected, troubleshooting usually comes down to the same small group of commands. You check whether the service is running, look through its logs, confirm that it is listening on the correct port, test the network, and then check whether CPU, memory, or disk usage is causing the problem. In this chapter, we'll work through ten commands you will use again and again when managing Linux servers: systemctl, journalctl, ss, ip, curl, ps, free, df, du, and grep.

Most compose.yaml files slowly turn into long, copy-pasted blocks with fragile startup dependencies. Docker Compose includes several built-in features that can keep your stack cleaner, more reusable, and predictable. Imagine a small web stack with a Python app, a worker, PostgreSQL, and an Nginx proxy defined in a single compose.yaml file. As the stack grows, you end up repeating the same settings across services.

DevOps job listings often mention dozens of tools, from Docker and cloud-init to monitoring and automation platforms. If you are just getting started, it can be difficult to understand what a DevOps engineer actually does with these tools on a real Linux server.

A Docker host can run reliably for months and still fill its disk overnight or expose a port to your firewall that should have been blocked. These 12 practical tips use docker system prune, daemon.json, restart policies, and health checks to help prevent those problems. Imagine receiving a disk-space alert from a server that has been running the same containers for months.

Edge servers with 1 GB of RAM and a unreliable, slow uplink need more than a general-purpose container tool. In this guide, we’ll look at nerdctl, balenaEngine, Incus, systemd-nspawn, and K3s, including how to install each tool and when it makes more sense than Podman. Imagine you manage a few dozen small ARM boxes in shops, each with limited flash storage and a 4G connection that drops several times a day. Podman can run containers on these devices perfectly fine.

Most Linux interviews now describe a broken server and ask how you would fix it. Here are 10 real troubleshooting scenarios, solved step by step with lsof, df, journalctl, ss, ausearch, and dmesg. Linux interviews used to be full of definition questions, such as what the chmod command does or which file stores user passwords.

Paying a WhatsApp API provider just to send server alerts becomes expensive as your scripts send more messages. Here's how to self-host OpenWA on Linux with Docker Compose, link a number, and send messages and webhooks through its REST API. Imagine a backup job fails at 2 AM on one of your servers, and the alert email lands in a mailbox nobody checks until morning, because email is where every other notification goes too.

When a package upgrade stops halfway through, your package manager can stay locked and leave many packages only partly installed. Here’s how to safely release the lock and repair the damage using fuser, dpkg, apt, dnf check, and rpm. Imagine you start a routine apt upgrade or dnf upgrade on a server over SSH, your Wi-Fi drops for ten seconds, and when you reconnect, the upgrade is no longer running.

Squid records every request that passes through the proxy in access.log, but reading raw epoch timestamps won't tell you which client is using most of your bandwidth. Here's how to load that log into GoAccess and view it as a live dashboard behind Nginx. If you run a Squid proxy for an office, a lab, or a group of build servers, sooner or later someone asks why the internet is slow, and the honest answer is usually "let me check the logs".

Most AI assistants on Linux can explain how to switch your Wi-Fi but can’t actually do it. openKylin 3.0 ships KylinBot and the Xiao K assistant, so we’ll test whether they really change network, Bluetooth, and display settings. If you have used an AI chatbot for Linux work, you have probably had it tell you exactly which nmcli command to run, and then you still had to open a terminal and type it yourself.