Mid level

This part follows junior administration. You already create users, bring up services and schedules, and write simple scripts that do the job. Here we drop one level down: scripts that do not fall over on the first error, storage and filesystems, networking from the interface to the route, boot and the kernel, monitoring and the security of a single host. The commands are the same, but now what happens underneath them matters.

What you need. A separate Linux system you can afford to break: a virtual machine or a dedicated server where you are root and can edit the bootloader, rebuild the network, and crash services with no consequences for your working machine. Ubuntu or any systemd distribution will do. Break it, roll back the snapshot or reinstall.

How to read. Chapters go in order, each builds on the previous one. The "how it works" boxes are a second layer for those curious about how things work underneath; you can skip them and come back later. Each chapter ends with exercises and a short summary.