Linux Café

Introduction to journalctl Filtering

I’ve been using journalctl for years, and I’ve learned that it can be overwhelming if you don’t know how to filter the noise. By default, journalctl displays a vast amount of information that may not be relevant to your current needs. In this article, I’ll share how I tame the noise in journalctl using custom filters and priorities.

Understanding journalctl Basics

Before we dive into filtering, let’s cover some journalctl basics. The command journalctl is used to query the systemd journal, which stores log messages from various system components, including systemd services, kernel messages, and other system logs. I usually start with a simple command to view the most recent journal logs:

Introduction to Log Noise

I’ve seen this go wrong when dealing with large systems - log files can quickly become overwhelming. In my experience, log noise is a significant issue, especially with the increasing complexity of systems and applications. Log noise refers to the irrelevant or redundant data in log files that can make it difficult to find the information you need. To tackle this, I usually start with jq and yq, two powerful command-line tools for parsing JSON and YAML data.

Introduction to DNS Resolution Issues

I’ve had my fair share of DNS resolution issues in my homelab over the years. Recently, I switched from using a single DNS resolver to a combination of Unbound and dnsmasq. This setup has been working well for me, but I’ve still encountered some issues that required troubleshooting. The real trick is identifying the root cause of the problem, which can be tricky.

Understanding Unbound and dnsmasq

Unbound is a recursive DNS resolver that provides a secure and private way to resolve domain names. It’s designed to be fast, efficient, and highly configurable. Dnsmasq, on the other hand, is a lightweight DNS forwarder and DHCP server. I’ve seen this go wrong when people don’t configure them correctly, so it’s essential to understand how they work together. In practice, using Unbound and dnsmasq together provides a good balance between security and performance.

Introduction to Slow Boot Times

I’ve had my fair share of slow boot times on Linux. When I upgraded my desktop to the latest version of my distribution in 2025, I noticed some new systemd services that were slowing down my boot process. The real trick is identifying which services are causing the issue. After digging around, I found that some of these services weren’t essential for my daily usage, and disabling them made a significant difference.

Introduction to Btrfs Send and Receive

I’ve been working with Btrfs for a while now, and I have to say, its send and receive functionality is one of my favorite features. It makes efficient backups and data replication across systems a breeze. However, like any complex operation, things can go wrong, and you’re left with incomplete or corrupted data. That’s where having a safety net like rsync comes in handy.

Introduction to Container Logs

I’ve been running a homelab with various self-hosted services for a while now, and managing container logs has been a challenge. With containerization making it easy to spin up multiple containers, keeping track of their logs can be overwhelming. In my experience, using Podman and systemd-journald has been a game-changer for taming container logs.

What are Container Logs?

Container logs are essentially the output of a container’s stdout and stderr streams. They contain valuable information about the container’s execution, such as errors, warnings, and debug messages. By default, container logs are stored in the container’s filesystem, which can lead to log rotation issues and make it difficult to manage logs across multiple containers. I’ve seen this go wrong when logs start filling up the container’s disk space, causing all sorts of issues.

Introduction to Podman Container Networking

I’ve been working with Podman for a while now, and I’ve found that networking issues can be a real pain point. When containers can’t communicate with each other or the host machine, it’s frustrating and can cause downtime. In this article, I’ll show you how to use the ss and nftables commands to troubleshoot Podman container networking issues.

Understanding Podman Networking

Before we dive into troubleshooting, it’s essential to understand how Podman handles networking. By default, Podman uses a bridge network, which allows containers to communicate with each other and the host machine. You can verify this by running podman network ls, which lists all available networks.

Introduction to Disk Space Management

I’ve been running a homelab server for a while now, and one thing that’s always been a challenge is managing disk space. With multiple services and projects running on my server, it’s easy to lose track of disk usage. I’ve seen this go wrong when you’re not paying attention, and suddenly you’re scrambling to free up space. Recently, I started exploring ways to better manage my disk space, and I stumbled upon btrfs snapshots and quotas. In practice, these features have been a game-changer for me.

Introduction to tmux

I’ve been using Linux for years, and one thing that’s made a huge difference in my productivity is being able to manage multiple terminal sessions efficiently. For me, tmux has been a game-changer. If you’re not familiar with it, tmux is a terminal multiplexer that lets you create and manage multiple terminal sessions from a single window. In this article, I’ll share some of my favorite tmux config tweaks that have helped me streamline my workflow.

Introduction to DNS Troubles

I’ve been running my homelab for years, and one thing that still gets me is DNS troubles. Last year, I decided to set up systemd-resolved and dnsmasq to manage my home network’s DNS. The idea was to use systemd-resolved as the primary resolver and dnsmasq as a caching layer to improve performance. Sounds simple, but it didn’t quite work out that way.

Setting Up systemd-resolved

To start, I enabled systemd-resolved on my Ubuntu-based server. This involved editing the /etc/systemd/resolved.conf file to set the DNS servers and domains. I opted for Cloudflare’s DNS servers - they’re known for being fast and secure.