Getting Started with Linux cgroups: A Practical Guide

What are cgroups?

They're a Linux kernel feature that allows the allocation, limiting and prioritisation of system resources across processes. They are a foundation for container technologies like Docker and Kubernetes.

The first thing is to install cgroup-tools. This package is a collection of command-line utilities for managing and interacting with Linux control groups or cgroups.

$ sudo apt update
$ sudo apt install -y cgroup-tools

To test things are working we can run a command like lscgroup which lists all the current cgroups configured on the system. The output is in the format

controler:path

Where the cgroup controller, or subsystem, is before the colon, e.g., cpu, memory, and the path in the cgroup hierarchy after the colon. We can also list cgroups by process ID or PID. For example:

$ sudo cat /proc/1/cgroup

This lists the cgroups associated with processes with PID 1, or the first process started at boot.

bernie@ubuntu:~$ sudo cat /proc/1/cgroup
13:memory:/init.scope
12:devices:/init.scope
11:freezer:/
10:cpuset:/
9:rdma:/
8:perf_event:/
7:pids:/init.scope
6:cpu,cpuacct:/init.scope
5:blkio:/init.scope
4:hugetlb:/
3:misc:/
2:net_cls,net_prio:/
1:name=systemd:/init.scope
0::/init.scope