Control groups

Google's own container journey started in 2006 when two of their engineers made a start on the control groups (cgroups) project. This is the Linux kernel feature which makes it possible to isolate resources such as RAM, CPU, networking, and disk I/O for a collection of processes. cgroups was initially released in 2007, and in early 2008 the functionality was merged into the Linux kernel mainline version 2.6.24.

You can find the release notes for version 2.6.24 of the Linux kernel at https://kernelnewbies.org/Linux_2_6_24. You can find information about the introduction of cgroups at point 10 in the Important things list where it discusses the framework that allows cgroups to hook into the kernel.