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When dealing with network connectivity issues in Linux, I’ve found the ss command to be one of the most useful tools in my toolkit. ss stands for “socket statistics” and is used to dump socket statistics. It can display stats for PACKET sockets, TCP sockets, UDP sockets, DCCP sockets, RAW sockets, Unix domain sockets, and more. In practice, this command has helped me identify and resolve a wide range of network connectivity issues.
I’ve seen this go wrong when running a multi-service Linux host - local port conflicts can be a real headache. These conflicts arise when two or more services attempt to bind to the same port, causing one or more of them to fail. To troubleshoot local port conflicts, I usually start with the ss command and nftables on a Linux system.
A port conflict occurs when a service tries to bind to a port that is already in use by another service. This can happen when multiple services are configured to use the same port, or when a service is not properly configured to use a unique port. Don’t bother with the traditional netstat command - the ss command is a more modern replacement.
I’ve seen this go wrong when people expose their homelab services directly to the internet - it’s a security risk waiting to happen. Exposing multiple services can make them vulnerable to attacks and unauthorized access. One way to mitigate this risk is to use a reverse proxy, which acts as an intermediary between your services and the internet. In practice, this means you can expose a single IP address and port to the internet, while keeping your services hidden behind the reverse proxy.
[Read More]I’ve seen systemd-resolved cause its fair share of issues with split DNS and local hostnames, but it’s actually a powerful tool for managing DNS resolution on Linux systems. As part of the systemd ecosystem, it aims to improve the DNS resolution process and provide better integration with other systemd services.
Split DNS, or split-horizon DNS, is a technique used to provide different DNS responses based on the client’s location. This is commonly used in environments where internal and external DNS zones need to be separated - think of a company with an internal DNS zone for its internal network and a separate external DNS zone for its public-facing services. Don’t bother with split DNS if you don’t need it, but if you do, systemd-resolved can be configured to handle it.
[Read More]I’ve seen container log management become a real challenge for many Linux administrators. As the number of containers grows, so does the volume of logs, making it tough to keep track of important events and debug issues. In my experience, using the right tools and techniques can make all the difference. In this article, I’ll share how to use Podman and systemd-journald to manage container logs effectively.
[Read More]I’ve seen this go wrong when you’re managing multiple SSH connections to various servers - it can quickly lead to a tangled mess of SSH config files. You end up with a dozen different servers, each with its own set of configuration options, and it’s a nightmare to keep track of which server uses which settings. Don’t bother with manual editing of the SSH config file; there are better ways to organize your connections.
[Read More]I’ve seen this go wrong when working with mixed-distro environments - managing package dependencies can become a complex task. Apt pinning is a feature in Debian-based systems that allows you to control the package versions installed on your system. This is particularly useful when you need to ensure that specific packages are installed from a particular repository or at a specific version.
The real trick is to understand how apt pinning works. It assigns a priority to each package version, and the package with the highest priority is the one that will be installed. You can set priorities using the /etc/apt/preferences file or by creating a new file in the /etc/apt/preferences.d/ directory. Don’t bother with creating a new file unless you have a lot of packages to pin - the /etc/apt/preferences file is usually sufficient.
I’ve seen this go wrong when you have multiple SSH connections to manage - it’s easy to end up with a messy ~/.ssh/config file. Don’t bother with manual editing; there are better ways to organize your SSH config. The real trick is to use the features already available in OpenSSH.
One approach to cleaning up your SSH config is to use include files, a feature available in OpenSSH 7.3 and later. This lets you split your config into multiple files, each containing a subset of your hosts. For example, you can create separate files for personal, work, and homelab servers. To use include files, add the following line to your ~/.ssh/config file:
I’ve seen this go wrong when a Linux system encounters a critical issue during boot - it drops into emergency mode. This mode provides a minimal environment for troubleshooting and repair, allowing you to diagnose and fix issues that prevent the system from booting normally. In this article, we’ll explore how to troubleshoot failed mounts in emergency mode with systemd.
Emergency mode is a special boot target in systemd that provides a basic environment for troubleshooting. When a system enters emergency mode, it means that an error occurred during the boot process, and the system was unable to mount the root filesystem or other critical filesystems. The real trick is to understand that, in emergency mode, you’ll have access to a root shell, but many system services will not be started.
[Read More]I’ve seen this go wrong when a Linux system fails to boot due to a broken initramfs - it can be a real headache, especially if you rely on your system for daily work or critical services. The recent updates to the Linux kernel and initramfs tools may have introduced compatibility issues for some users, making it crucial to understand how to recover from such failures.
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