Understanding the structure of cgroups Version 1

To understand the structure of cgroups, you'll need to understand some of the cgroups terminology. Let's start with just a few terms that you need to know:

• cgroups: The term cgroup has two different meanings. What concerns us most is that a cgroup is a collection of processes. The processes within each cgroup are bound to limits and parameters that are defined within the cgroup filesystem. (We'll talk more about the cgroup filesystem in a bit.) The term cgroup can also refer to the Linux kernel code that implements cgroups technology.
• services: These are groups of processes that are started by systemd, and that are configured by the different unit configuration files. The individual processes in a service are started and stopped as one set. An example of a service would be the Apache web server service, which would be called httpd.service or apache2.service. (Okay, you already knew this, but I told you again...