linux

Kernel Parameters and sysctl

sysctl lets you read and modify hundreds of kernel parameters at runtime — memory management, network stack tuning, security hardening. Understanding what to change and why is what kernel tuning actually is.

The /sys Filesystem and udev

/sys exposes the kernel's hardware device tree as a filesystem. Every device, driver binding, and hardware parameter is visible and writable. udev sits on top and automates responses to hardware events. Together they are the kernel's live hardware interface.

The /proc Filesystem — In Depth

/proc is a virtual filesystem generated on the fly by the kernel. Nothing in it exists on disk. It gives you a live window into CPU info, memory state, process details, network state, and the kernel's own runtime configuration.

Kernel Module Management

The Linux kernel uses a modular system — most functionality loads as separate modules at runtime without rebooting. Understanding lsmod, modprobe, blacklisting, and module configuration gives you real control over what the kernel is doing.

Log Management

When something goes wrong on a Linux system, logs are where you find out why. Knowing where logs live, how to read and filter them efficiently, and how to stop them eating all your disk space is core sysadmin knowledge.

Environment Variables and the Shell

Every time you open a terminal the shell sets up an environment — variables that control how it and every program you run behave. Understanding PATH, export, and shell startup files makes everything click into place.

Firewall — iptables and ufw

The Linux firewall is built into the kernel. iptables has been the tool to configure it for decades. ufw makes the common cases much simpler. This post covers how it all fits together.

Cron and Scheduled Tasks

cron is the classic Linux task scheduler. It runs commands on a schedule — every minute, every hour, every day, or any combination you define. Understanding the syntax and the gotchas makes it reliable.

Users and Groups — In Depth

The earlier permissions post covered the basics. This one goes deeper — how Linux stores user accounts in /etc/passwd and /etc/shadow, how to manage users properly, and how the sudoers file actually works.