sysfscgroups

Sysfscgroups refers to the sysfs-based interface used to manage Linux control groups (cgroups). Through the sysfs filesystem, typically mounted at /sys/fs/cgroup, the kernel exposes cgroup hierarchies as directories and control files. This interface enables inspecting the structure of cgroups, creating and deleting groups, and attaching processes to specific groups. It also provides a location to view resource usage and to adjust limits by writing values to appropriate control files within each cgroup.

Cgroups are a kernel feature that allow limiting, accounting for, and isolating the resource usage of processes. Systems may implement cgroups in two major ways: cgroup v1, which uses separate hierarchies for different controllers (such as CPU, memory, and I/O), and cgroup v2, which introduces a unified hierarchy with a common set of control files. The sysfscgroups interface adapts to these architectures, exposing the relevant directories and files in a way that is consistent with the active cgroup model.

Typical operations include creating a new cgroup by creating a directory under the appropriate hierarchy, adding a process to a cgroup by moving its PID into a tasks or cgroup.procs file, and configuring limits by writing values to specific limit or max files. Practical management is often performed by higher-level tools and services (for example, container runtimes or systemd), which interact with the sysfscgroups interface or with dedicated libraries to manage cgroups.

Access to the sysfscgroups interface generally requires elevated privileges (such as CAP_SYS_ADMIN). The exact layout and file names can vary between kernel versions and distributions, so consult system documentation for specifics.

See also: cgroups, sysfs, /sys/fs/cgroup, Linux namespaces.