Unified Control Group hierarchy (cgroup v2)

A Control Group (cgroup) is a Linux kernel feature to hierarchically organize processes and distribute system resources between them. Control Groups are used extensively to implement a container runtime, and by systemd.

AL2 supports cgroupv1, and AL2023 supports cgroupv2. This is notable if running containerized workloads, such as when Using AL2023 based Amazon ECS AMIs to host containerized workloads.

Although AL2023 still includes code that can make the system run using cgroupv1, this is not a recommended or supported configuration, and will be completely removed in a future major release of Amazon Linux.

There is extensive documentation regarding the low-level Linux Kernel interfaces, as well as systemd cgroup delegation documentation.

A common use case outside of containers is for creating systemd units that have limits placed on the system resources they can use. For more information, see systemd.resource-control.