join_root_cgroup(9)

💅 join_root_cgroup(9) — Kernel API Manual

okay so bestie, welcome to the join_root_cgroup manpage, section 9, straight out of the Kernel API Manual ✨ this one's short and sweet, so let's go 🫶

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🌸 NAME 🌸

join_root_cgroup — literally just, join the root cgroup. that's the whole vibe 💖

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🎀 SYNOPSIS 🎀

int join_root_cgroup (void );

like, yes, that's the entire signature. she's minimal. she's iconic. 👑

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🦋 ARGUMENTS 🦋

• void — no arguments, bestie. zero. none. she takes nothing and she needs nothing 🙈

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⭐ DESCRIPTION ⭐

So here's the tea: this function joins the root cgroup. that's it, that's the function 💀 no cap, that's the entire description.

On success, it returns 0, otherwise on failure it returns 1. so like, 0 = slay, 1 = not slay 😭 keep that in mind for your error checking, okay? 🍓

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🔥 SEE ALSO 🔥

Kernel file ./tools/testing/selftests/bpf/cgroup_helpers.c — that's where she lives, go read the source if you're nosy (respectfully) 💜

and then the whole friend group, fr fr:

• enable_controllers(9)
• write_cgroup_file(9)
• write_cgroup_file_parent(9)
• setup_cgroup_environment(9)
• join_cgroup(9)
• join_parent_cgroup(9)
• set_cgroup_xattr(9)
• __cleanup_cgroup_environment(9)
• cleanup_cgroup_environment(9)
• get_root_cgroup(9)
• create_and_get_cgroup(9)
• get_cgroup_id_from_path(9)
• setup_classid_environment(9)
• set_classid(9)
• join_classid(9)
• cleanup_classid_environment(9)
• get_classid_cgroup_id(9)
• get_cgroup1_hierarchy_id(9)
• open_classid(9)

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bestie reminder: this page is filed under ./tools/testing/selftests/bpf and it's dated October 2026 — so like, mark your calendar or whatever 📅✨

that's the whole page, you ate it up, go join that root cgroup 💅🌈👑