Linux Security

Introduction to SSH Keys and Agents

I’ve seen many Linux users struggle with managing multiple remote systems, but SSH keys and agents can make a huge difference. By using SSH keys, you can authenticate to remote servers without entering a password, making it easier to manage multiple systems. In practice, this means you can quickly switch between systems without having to remember a bunch of passwords.

Generating SSH Keys

To start using SSH keys, you need to generate a key pair on your local system. I usually start with the ssh-keygen command to generate a key pair:

Introduction to SSH Connection Sharing

I’ve seen this go wrong when people don’t understand how SSH connection sharing works. It’s actually pretty simple: SSH connection sharing is a feature that allows you to reuse an existing SSH connection for multiple SSH sessions. This can significantly speed up your workflow, especially when working with remote servers. In this article, we’ll explore how to master SSH connection sharing using ControlMaster and ControlPersist.

Introduction to pgrep and pkill

When I’m managing background tasks and processes in Linux, I always reach for pgrep and pkill. These two commands are often overlooked, but they’re incredibly useful for searching for and managing processes by name. I’ve seen this go wrong when people use ps with grep - it’s just not as precise. With pgrep and pkill, you can avoid common mistakes when dealing with background tasks.

Introduction to Remote File Transfers

I’ve seen this go wrong when you’re trying to transfer files between machines, especially in scenarios where direct access is not possible. Using a jump host can simplify the process. A jump host, also known as a bastion host, is an intermediary server that you use to access other servers. In this article, we’ll explore how to use SSH and rsync over a jump host for secure and efficient remote file transfers.

Introduction to Log Rotation

Log rotation - it’s one of those tasks that’s easy to overlook, but can quickly become a major headache if you don’t stay on top of it. I’ve seen this go wrong when log files consume all the available disk space, bringing a system to its knees. With many Linux distributions now using systemd-journald as the default logging mechanism, understanding how to manage log rotation is more important than ever.

Introduction to Log Rotation

I’ve seen log files grow out of control and bring down entire systems, so log rotation is something I take seriously. It’s a crucial aspect of Linux system maintenance, ensuring that log files don’t consume all available disk space. On busy systems, logs can fill up quickly, leading to issues with system performance and even causing services to fail.

Understanding Log Rotation

Log rotation involves periodically switching out log files, typically by renaming the current log file and starting a new one. This process can be configured to occur at set intervals, such as daily or weekly, and can also be triggered by the size of the log file. Most Linux distributions come with a log rotation system pre-configured, often using the logrotate utility. Don’t bother with manual log rotation unless you have a specific reason to do so - logrotate is a well-tested and reliable tool.

Introduction to systemd Service Restart Behavior

I’ve seen this go wrong when a service is not properly configured - systemd, the core component of most modern Linux distributions, is responsible for managing system services. One of its key features is the ability to automatically restart services that fail or terminate unexpectedly, controlled by the Restart directive in the service unit file. However, I’ve found that the Restart directive alone may not be sufficient to handle all scenarios, which is where the Retry and Timeout options come into play.

Introduction to Shared Directory Permissions

When working with shared directories in Linux, permissions can quickly become a complex issue. I’ve seen this go wrong when multiple users need to collaborate on the same project, and suddenly, nobody can access the files they need. The setgid bit and Access Control Lists (ACLs) are two powerful tools for managing these permissions. In this article, we’ll explore how to troubleshoot broken permissions on shared directories using setgid and ACLs.

Introduction to systemd-resolved

I’ve been using systemd-resolved for a while now, and I have to say, it’s a game-changer when it comes to managing DNS resolution on Linux systems. As of 2026, it’s become a crucial component in many Linux distributions, including Ubuntu, Debian, and Fedora. In this article, I’ll walk you through how to use systemd-resolved with multiple DNS servers and split horizon DNS, including some practical examples and troubleshooting notes.

Introduction to Dependency Management

As someone who’s spent years running Linux systems, I can tell you that dependency management is crucial for maintaining a healthy and stable system. You’re probably already familiar with keeping your packages up to date, but sometimes you need to pin specific packages to prevent them from being updated. This can help maintain system stability or prevent potential security issues. In this article, I’ll walk you through how to use apt-mark to pin packages in Debian-based systems.